Dissertations / Theses: 'Intraocular pressure'

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Rai, Gurjeet Kaur. "Accommodation and intraocular pressure." Thesis, Aston University, 2007. http://publications.aston.ac.uk/14645/.

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The relationship between accommodation and intraocular pressure (IOP) has not been addressed as a research question for over 20 years, when measurement of both of these parameters was less advanced than today. Hence the central aim of this thesis was to evaluate the effects of accommodation on lOP. The instrument of choice throughout this thesis was the Pulsair EasyEye non-contact tonometer (NCT) due principally to its slim-line design which allowed the measurement of lOP in one eye and simultaneous stimulation of accommodation in the other eye. A second reason for using the Pulsair EasyEye NCT was that through collaboration with the manufacturers (Keeler, UK) the instrument's operational technology was made accessible. Hence, the principle components underpinning non-contact lOP measures of 0.1mmHg resolution (an order of magnitude greater than other methods) were made available. The relationship between the pressure-output and corneal response has been termed the pressure-response relationship, aspects of which have been shown to be related to ocular biometric parameters. Further, analysis of the components of the pressure-response relationship together with high-speed photography of the cornea during tonometry has enhanced our understanding of the derivation of an IOP measure with the Pulsair EasyEye NCT. The NCT samples the corneal response to the pressure pulse over a 19 ms cycle photoelectronically, but computes the subject's lOP using the data collected in the first 2.34 ms. The relatively instantaneous nature of the lOP measurement renders the measures susceptible to variations in the steady-state lOP caused by the respiratory and cardiac cycles. As such, the variance associated with these cycles was minimised by synchronising the lOP measures with the cardiac trace and maintaining a constant pace respiratory cycle at 15 breathes/minute. It is apparent that synchronising the lOP measures with the peak, middle or trough of the cardiac trace significantly reduced the spread of consecutive measures. Of the 3 locations investigated, synchronisation with the middle location demonstrated the least variance (coeflicient of variation = 9.1%) and a strong correlation (r = 0.90, p = <0.001) with lOP values obtained with Goldmann contact tonometry (n = 50). Accordingly IOP measures synchronised with the middle location of the cardiac cycle were taken in the RE while the LE fixated low (L; zero D), intermediate (I; 1.50 D) and high (H; 4 D) accommodation targets, Quasi-continuous measures of accommodation responses were obtained during the lOP measurement period using the portable infrared Grand Seiko FR-5000 autorefractor. The lOP reduced between L and I accommodative levels by approximately 0.61 mmHg (p <0.00 I). No significant reduction in IOP between L and H accommodation levels was elicited (p = 0.65) (n = 40). The relationship between accommodation and lOP was characterised by substantial inter-subject variations. Myopes demonstrated a tendency to show a reduction in IOP with accommodation which was significant only with I accommodation levels when measured with the NCT (r = 0.50, p = 0.01). However, the relationship between myopia and lOP change with accommodation reached significance for both I (r = 0.61, p= 0.003) and H (r = 0.531, p= 0.0 1) accommodation levels when measured with the Ocular blood Flow Analyser (OBFA). Investigation of the effects of accommodation on the parameters measured by the OBFA demonstrated that with H accommodation levels the pulse amplitude (PA) and pulse rate (PR) responses differed between myopes and emmetropes (PA: p = 0.03; PR: p = 0.004). As thc axial length increased there was a tendency for the pulsatile ocular blood flow (POBF) to reduce with accommodation, which was significant only with H accommodation levels (r = 0.38, p = 0.02). It is proposed that emmetropes arc able to regulate the POBF responses to changes in ocular perfusion pressure caused by changes in lOP with I (r = 0.77, p <0.001) and H (r = 0.73, p = 0.001) accommodation levels. However, thc relationship between lOP and POBF changes in the myopes was not correlated for both I (r = 0.33, p = 0.20) and H (r = 0.05, p = 0.85) accommodation levels. The thesis presents new data on the relationships between accommodation, lOP and parameters of the OBFA,: and provides evidence for possible lOP and choroidal blood flow regulatory mechanisms. Further the data highlight possible deficits in the vascular regulation of the myopic eye during accommodation, which may play a putative role in the aetiology of myopia development.

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Johansson, Gabriella. "Effect of phacoemulsification on intraocular pressure." Thesis, Linnéuniversitetet, Institutionen för naturvetenskap, NV, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-12619.

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Aim: The purpose of this study was to evaluate whether there is an effect of cataractsurgery with phacoemulsification on IOP after one week of surgery. To investigate whether there is a correlation between Axial length (AL), Anterior chamber depth ACD, K-readings with preoperative (preop) and postoperative (postop) IOP. Methods: The subjects for this study were extracted from the records at the Eye department in Kalmar Hospital, Sweden. From an existing data file 72 eyes out of 72 subjects were then analysed. The subjects were divided into 4 groups based on the axial length of the eyes, forstatistical analysis in Microsoft Excel and Statistica 6.0. Preoperative and postoperative IOP was evaluated to look for statistical significance. IOP was compared to AL, ACD and Kreadingsto look for any correlations. Results: Preoperative IOP and postoperative IOP did not show any statistically significant difference after phacoemsulification, p > 0.05. There was no statistical significance orcorrelation for the axial length, ACD and K-readings compared to pre and post IOP,p > 0.05.Conclusion: There was no change in IOP before and after surgery. This study did not show any significance between the preoperative and postoperative mean IOP after cataract surgery. Axial length was not a factor to the intraocular pressure. There was neither any statistical significance nor correlation between the anterior chamber depth and K-readings in relation to IOP.

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Morgan, Andrew J. "Analysis of the intraocular pressure pulse." Thesis, Aston University, 2003. http://publications.aston.ac.uk/14542/.

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This thesis was concerned with investigating methods of improving the IOP pulse’s potential as a measure of clinical utility. There were three principal sections to the work. 1. Optimisation of measurement and analysis of the IOP pulse. A literature review, covering the years 1960 – 2002 and other relevant scientific publications, provided a knowledge base on the IOP pulse. Initial studies investigated suitable instrumentation and measurement techniques. Fourier transformation was identified as a promising method of analysing the IOP pulse and this technique was developed. 2. Investigation of ocular and systemic variables that affect IOP pulse measurements In order to recognise clinically important changes in IOP pulse measurement, studies were performed to identify influencing factors. Fourier analysis was tested against traditional parameters in order to assess its ability to detect differences in IOP pulse. In addition, it had been speculated that the waveform components of the IOP pulse contained vascular characteristic analogous to those components found in arterial pulse waves. Validation studies to test this hypothesis were attempted. 3. The nature of the intraocular pressure pulse in health and disease and its relation to systemic cardiovascular variables. Fourier analysis and traditional parameters were applied to the IOP pulse measurements taken on diseased and healthy eyes. Only the derived parameter, pulsatile ocular blood flow (POBF) detected differences in diseased groups. The use of an ocular pressure-volume relationship may have improved the POBF measure’s variance in comparison to the measurement of the pulse’s amplitude or Fourier components. Finally, the importance of the driving force of pulsatile blood flow, the arterial pressure pulse, is highlighted. A method of combining the measurements of pulsatile blood flow and pulsatile blood pressure to create a measure of ocular vascular impedance is described along with its advantages for future studies.

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Hallberg, Per. "Applanation Resonance Tonometry for Intraocular Pressure Measurement." Doctoral thesis, Umeå : Tillämpad fysik och elektronik, Umeå univ, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-784.

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Chang, Jason (Yin-Hao). "Mechano-regulation of intraocular pressure through eNOS." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/58342.

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Glaucoma is the leading cause of irreversible blindness worldwide, and is characterized by elevated intraocular pressure (IOP) caused by increased resistance to aqueous humor outflow. The majority of outflow resistance is generated near the inner wall endothelium of Schlemm’s canal (SC). The inner wall experiences a basal-to-apical directed flow as aqueous humor crosses the outflow pathway. As IOP increases, the outflow pathway responds in a pressure-dependent manner, resulting in the expansion of the trabecular meshwork (TM) and the collapse of SC. This effectively reduces the cross-sectional area of the SC lumen and increases the shear stress experienced by SC cells, reaching levels known to activate endothelial nitric oxide synthase (eNOS) in vascular endothelia. Our central hypothesis examines the role of eNOS as part of a dynamic mechano-regulatory feedback system to regulate the outflow resistance sites through nitric oxide (NO) production to maintain IOP homeostasis. We firstly demonstrated the physiological role of NO and eNOS in regulating aqueous humor outflow through the use of NO-donor and NOS-inhibitors. We also demonstrated that spatial variations in eNOS expression in the SC correlates with regions of greater outflow in the TM. Furthermore, we developed NO-sensitive biosensors to detect changes in NO production in response to elevated IOP, showing that NO production was pressure-dependent. Finally, we demonstrated that targeted delivery of NO to the outflow resistance sites in the TM results in a ~3-fold increase in outflow facility. Taken together, these studies reveal that eNOS plays a crucial regulatory role in conventional outflow physiology by modulating outflow resistance through NO production. This mechano-regulatory feedback mechanism appears to be altered in glaucoma, and thus leads to ocular hypertension and pathogenesis of the disease. Therefore, targeting the NO-regulatory machinery within the outflow pathway may provide a promising therapeutic target for treating glaucoma.

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Gerzenstein, Sabrina Melisa. "Pharmacogenomics of the Intraocular Pressure Response to Glucocorticoids." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_theses/285.

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Glucocorticoids (GCs) have been widely used as a therapeutic agent for diverse inflammatory ocular diseases. However, a high percentage of patients undergoing this treatment develop high intraocular pressure (IOP), which if left unsupervised may lead to glaucoma. It is believed that the IOP elevation in response to GC treatment has a genetic determinant. In order to test this hypothesis, we analyzed in 52 patients the presence of single nucleotide polymorphisms (SNPs) in the glucocorticoid receptor gene (GR), the principal mediator of GCs uptake by the cells. We studied six GR SNPs previously reported to be associated with sensitivity and resistance to GCs: GluArg22/23GluLys (codon 22-23), Asn363Ser (codon 363), IVS2+646C>G (intron 2/BclI), IVS3-46G>C (intron 3), IVS4-16G>T (intron 4), Asn766Asn (Codon 766). Nevertheless, the results of this preliminary study did not show any specific correlation between SNPs in the GR gene and IOP elevation. Therefore, we proceeded to perform a whole genome SNP screen with the DNA samples of these patients to search for possible target genes responsible for the elevated IOP after GC treatment. As a result, we identified forty-eight SNPs in thirty-three genes that correlate with the high IOP response. The gene showing the strongest association is a poorly known G-protein coupled receptor. In addition, four SNPs hit a single transporter gene. Other candidate genes identified are a translation elongation factor, an F-box protein, an oxysterol binding protein, and a solute carrier family gene. These results support our hypothesis that IOP elevation following GC treatment is a genetically determined response. GCs are a common treatment for innumerable medical conditions; we believe that a genetic association between GC treatment and its physiological response may be important for improving treatment management and drug development for retinal diseases as well as for other medical ailments. However, further studies need to be performed to analyze in depth the association between the candidate genes identified in this study and the steroid response.

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Jóhannesson, Gauti. "Intraocular pressure : clinical aspects and new measurement methods." Doctoral thesis, Umeå universitet, Oftalmiatrik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-40383.

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Intraocular pressure (IOP) measurement is a routine procedure and a fundament in glaucoma care. Elevated IOP is the main risk factor for glaucoma, and to date, reduction of IOP is the only possible treatment. In a retrospective clinical material, the prevalence of open angle glaucoma was estimated on the west coast of Iceland. IOP measurement and optic nerve head examination were used to capture glaucoma suspects, within the compulsory ophthalmological examination for the prescription of eye glasses. The results were mainly in agreement with a recent prospective study in the same region. This indicated that retrospective data, under certain conditions, may contribute with useful information on the prevalence of glaucoma. However, normal tension glaucoma is underestimated if perimetry and/or fundus photography are not included in the examination. Three studies focused on the measurement of IOP. Goldmann applanation tonometry (GAT) is the standard method. GAT is affected by corneal properties, e.g. central corneal thickness (CCT) and corneal curvature (CC). Refractive surgery changes these properties. This has put focus on how corneal biomechanics translate into tonometric errors and stimulated the development of new methods. As a result, Pascal ® Dynamic Contour Tonometry (PDCT) and Icare® rebound tonometry have been introduced. A method under development by our research group is Applanation Resonance Tonometry (ART). It is based on resonance technology and estimates IOP from continuous measurement of force and contact area. Comparison of PDCT, Icare and GAT in a prospective study showed that the concordance to GAT was close to the limits set by the International Standard Organization (ISO) for PDCT, while Icare was outside the limits. To investigate if laser-assisted subepithelial keratectomy (LASEK) affects tonometry, a study was performed where measurements with GAT, PDCT and ART were obtained before, three and six months after LASEK. The hypothesis was that PDCT and ART would be less affected by LASEK than GAT. The results showed a statistically significant reduction of measured IOP three and six months after LASEK for all tonometry methods. Change in visual acuity and IOP between three and six months suggested a prolonged postoperative process. A servo-controlled prototype (ART servo) was developed. A study was undertaken to assess the agreement of ARTservo and a further developed v manual prototype (ART manual) with GAT. The study design was in accordance with the requirements of the ISO standard for tonometers. ARTmanual fulfilled the precision requirements of the ISO standard. ARTservo did not meet all the requirements of the standard at the highest pressure levels. Four tonometry methods, GAT, PDCT, Icare and ART, were investigated. None of them was independent of both CCT and CC. The inconsistencies in the results emphasize the importance of study design. A meta-analysis comprising healthy eyes (IOP ≤ 21 mmHg) in the three papers, revealed age as an important confounder. In summary, glaucoma prevalence in Iceland was investigated and the results indicated that a retrospective approach can contribute with meaningful information. ART and PDCT had a similar agreement to GAT. ART manual fulfilled the precision requirements set by the ISO-standard, ARTservo and PDCT were close, while Icare was distinctly outside the limits. All tonometry methods were affected by LASEK and no method was completely independent of corneal properties.

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Bello, Simon Antonio. "Intraocular Pressure Sensing and Control for Glaucoma Research." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6466.

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Animal models of ocular hypertension are important for glaucoma research but come with experimental costs. Available methods of intraocular pressure (IOP) elevation are not always successful, the amplitude and time course of IOP changes are unpredictable and irreversible, and IOP measurement by tonometry is laborious. This dissertation focuses on the development and implementation of two novel systems for monitoring and controlling IOP without these limitations. The first device consists of a cannula implanted in the anterior chamber of the eye, a pressure sensor that continually measures IOP, and a bidirectional pump driven by control circuitry that can infuse or withdraw fluid to hold IOP at user-desired levels. A portable version was developed for tethered use on rats. The system was fully characterized and deemed ready for cage- or bench-side applications. The results lay the foundation for an implantable version that would give glaucoma researchers unparalleled knowledge and control of IOP in rats and potentially larger animals. Moreover, a novel mathematical technique was developed to efficiently analyze IOP records obtained using the pressure controlling device. The algorithm successfully yields the value of several parameters that influence ocular physiology and are commonly linked to glaucoma development. This unique methodology uses information regarding the amount of volume necessary to maintain IOP at different levels to quantify the outflow facility of perfused eyes. The use of this technology largely simplifies the investigator’s experimental set-up and cuts procedural times in half. The second device is an implantable pressure sensor for continuously monitoring IOP. The miniature system is equipped with pressure and temperature transducers, on-board amplifiers and a powerful microcontroller that ensure data quality. The sensor is able to obtain measurements with twice the accuracy and precision of any other IOP sensor used to date, avoid electronic drifts commonly seen in commercial sensing devices, and can potentially be used in a variety of animal models. The sensor was characterized and tested in alert rats for weeks on end. Data obtained with this device showed the presence of previously reported circadian rhythms, with IOP significantly increasing during nocturnal cycles. This technology provides researchers with an unprecedented tool to analyze IOP dynamics over time. The characterization of the amplitude, period and phase of the IOP profiles of normal and glaucomatous eyes may help establish a definitive correlation between ocular hypertension and glaucoma progression. While implantable systems provide investigators with essential physiological data, their implementation can be difficult. Challenges such as reduced operational lifetimes and limited data acquisition capabilities are commonly faced by most bio-devices. These limitations are frequently linked to small battery capacities, however the implementation of bigger batteries is not usually viable due to size requirements. Energy harvesting technologies have surfaced in recent years in an attempt to replace battery applications; however, most technologies provide low power densities and cannot deliver continuous telemetric operation. An innovative wireless powering system was developed to overcome these limitations. The technology uses radio frequency (RF) energy transfer to continuously harvest high energy levels. Taking advantage of the controlled environment under which most research animals are housed, RF transmitters are placed around the cage to form strong, omnidirectional electric fields. An especial antenna was designed to be worn by the animal and collect large energy levels, irrespective of animal movements and positioning. The system was tested on the implantable IOP sensor for weeks, providing robust performances and allowing the sensor to collect data continuously with high precision. The device consistently generated power densities much greater than those required by the sensor. The surplus of energy could be used to operate multiple sensors simultaneously, greatly increasing the investigator’s leverage. The technology is easily adaptable to other bio-sensors and has the potential to revolutionize the biomedical field.

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Polyzoev, Vasco. "HAND-HELD TONOMETER FOR TRANSPALPEBRAL INTRAOCULAR PRESSURE MEASUREMENT." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202517.

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This dissertation describes the development of a portable, hand-held tonometer for measurement of the intraocular pressure through the eyelid. The primary use of such device will be by people diagnosed with the eye disease glaucoma. Glaucoma is the second leading cause of blindness in the world and is asymptomatic to the patient in its early stages. This allows it to remain undiagnosed for prolonged periods, causing irreversible damage to the affected person's vision. Elevated intraocular pressure is the main risk factor associated with the development of glaucoma, and is currently the only symptom that is treatable for the slowing down or stopping of the progression to blindness caused by the disease. The effectiveness of the medications or procedures aimed at reducing the pressure to below risk levels is currently monitored through visits to the ophthalmologists' offices, which makes the frequent monitoring of the pressure inconvenient, expensive and sometimes impossible. Due to the variation of the pressure throughout the day and during different activities or food and beverage intake, the portability of the device is important in order to allow the user to carry it with them and take measurements as frequent as needed. The option to perform the measurement through the eyelid avoids direct contact with the eye, eliminating possible discomfort, the use of anesthetics, and the risk of contamination.Several designs and measuring concepts are evaluated using a custom made pressure regulation system. A series of prototypes have been built and tested and the results are reported in the respective sections of the dissertation. The final concept selected for the measurement technique was based on multiple force probe indentation and a custom MEMS-based force sensor for it was designed and tested.The main contributions of this dissertation are the design, fabrication and test of the prototype devices and the MEMS force sensors. The obtained results and experience described here can serve as a platform for further optimization and improvement of the device, and eventual development of a prototype capable of performing clinical research studies and passing FDA approval for home and clinical use.

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Ljubimova, Darja. "Biomechanics of the Human Eye and Intraocular Pressure Measurements." Doctoral thesis, KTH, Strukturmekanik, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11420.

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This thesis addresses the reliability of Goldmann-type applanation tonometers (GAT). It deals with the investigation of the relation between predicted intraocular pressure, IOPG and true pressure, IOPT. The problem of the accuracy of GAT readings has acquired special importance over the last two decades as new types of surgical procedures to correct vision disorders are being explored and gain universal acceptance. The overall aim of the present study is to assess the effects of individual variations in the corneal central thickness (CCT), material properties of the involved tissues and paracentral applanation on the accuracy of IOPG. Two finite element models have been constructed: a two-dimensional axisymmetric model of the cornea and a three-dimensional model of the whole corneoscleral envelope. Various material descriptions were adopted for the cornea in 2D, whereas the 3D model accounted for collagen microstructure and represented a hyperelastic ber reinforced material. Nonlinear analyses were carried out using the commercial general-purpose finite element software ABAQUS. An extensive literature survey and consultations with ophthalmologists and clinicians were the platform for establishing relevant modelling procedures. The results reveal a clear association between all considered parameters and measured IOPG. The effect of assumed CCT is highly dependent on the corneal material properties. Material model alone has a profound effect on predicted IOPG. Variations in tonometer tip application produce clinically signi cant errors to IOPG measurements. Potential effects of corneal stiffness and paracentral applanation on GAT readings are larger than the impact of CCT. The behaviour of the models is broadly in agreement with published observations. The proposed procedures can be a useful tools for suggesting the magnitudes of corrections for corneal biomechanics and possible human errors. The present modelling exercise has an ability to reproduce the behaviour of human cornea and trace it under IOP and GAT, providing potentially useful information on the distribution of stresses and strains. Some recommendations can be drawn in pursuit of the clinical imperatives of ophthalmologists.
QC 20100729

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Agar, Ashish Medical Sciences Faculty of Medicine UNSW. "Pressure effects on neurons: investigations into the pathogenesis of glaucoma." Awarded by:University of New South Wales. School of Medical Sciences, 2006. http://handle.unsw.edu.au/1959.4/31548.

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Cellular responses to changes in pressure are implicated in numerous disease processes. In glaucoma apoptosis of retinal ganglion cells (RGCs) is associated with elevated intra-ocular pressure (IOP), however the exact cellular basis of this link remains unclear. This research aimed to examine the direct response of neuronal cells to elevated hydrostatic pressure in terms of apoptosis. We developed an in vitro model consisting of a pressure chamber to adjust ambient hydrostatic pressure, a source of neuronal cells and methods to measure apoptosis in these cells. The neural cells examined were primary retinal cultures, four neuronal cell lines (B35, PC12, C17, NT2), and the RGC-5 cell line. Pressure conditions selected were within physiological limits; 100 mmHg above atmospheric pressure (as seen clinically in severe acute glaucoma) and extended in RGC-5 neurons to 30 mmHg (chronic glaucoma) and 15 mmHg (normal IOP). Apoptosis was detected by cell morphology and specific immunochemical markers: TUNEL and Annexin V. Caspase-3 activation, a known pathway of apoptosis, was also investigated in RGC-5 neurons. These fluorescent markers were detected and quantified by automated Laser Scanning Cytometry. Negative controls were treated identically except for the application of pressure, while positive controls were generated by treatment with a known apoptotic stimulus. The results showed that neurons responded to elevated hydrostatic pressure directly and that an apoptotic process was induced. There was a greater level of apoptosis in pressurised cells compared to the negative controls. This apoptotic effect at high pressures was seen in primary rat retinal cultures and in both undifferentiated (B35, C17, NT2, RGC-5) and differentiated (PC12, RGC-5) neuronal cell lines. RGC-5 neurons showed a graded response, proportionate to the level of pressure elevation, representative of the severity of analogous clinical settings (acute, chronic glaucoma & normal). RGC-5 neurons also showed increased activation of Capsase-3. Thus this pathway may play a role in pressure induced apoptosis. Our findings indicate that pressure alone may act as a stimulus for apoptosis in neuronal cells. We suggest the possibility of novel mechanisms of pressure related mechanotransduction and cell death, relevant to the pathogenesis of glaucoma.

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Lai, Wing-ki, and 黎穎琪. "Off anti-glaucoma medication study: changes in visual field, retinal nerve fiber layer thickness and riskestimation of glaucoma onset in 1 year follow up." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48333967.

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Objective: To examine the changes of visual field and retinal nerve fiber layer (RNFL) measurements and the risk of glaucoma progression before and after taking off intraocular pressure (IOP) lowering medication in Chinese patients with ocular hypertension. Design: Prospective study. Participants: 106 ocular hypertension patients (4 were excluded because there was no 1 year follow up examination). Method: All patients underwent visual field testing by Humphrey Field Analyser and Retinal Nerve Fiber Layer (RNFL) thickness measurement by a spectral-domain optical coherence tomography. Eyes without glaucomatous visual field defect and had an IOP ?30mmHg were instructed to stop taking IOP lowering medication and measurements of IOP, visual field and RNFL measurements were taken. Changes in the visual field mean deviation, average, superior and inferior RNFL thickness and the risk of developing glaucoma between the baseline and follow-up examinations were compared between the groups with and without stopping IOP lowering medications. Logistic regression was used to analyze the association between corneal hysteresis, ocular pulse amplitude and the onset of glaucoma. Results: There were 73 patients with IOP lowering medications taken off and 29 with continued medications. No significant differences were found in the changes of visual field mean deviation, average RNFL thickness and the risk of glaucoma progression (P=0.92, P=0.81, P=0.35, respectively) between the groups. Ocular pulse amplitude was a significant predictor of glaucoma development by functional (-0.61, P=0.047) and structural criteria (-0.74, P=0.024). Conclusion: There were no functional and structural changes in patients with ocular hypertension after stopping IOP lowering medications in one year. Low ocular pulse amplitude could be a predictive factor for the conversion from ocular hypertension to glaucoma. Clinicians should not prescribe IOP-lowering medication simply base on high IOP.
published_or_final_version
Medicine
Master
Master of Medical Sciences

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Nilsson, Emelie. "Changes in the intraocular pressure value, when wearing orthokeratology lenses." Thesis, University of Kalmar, School of Pure and Applied Natural Sciences, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:hik:diva-2280.

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Introduction: Quite new on the Swedish market are orthokeratology lenses, used for both correction and myopia control. At the moment there are 22 practitioners in Sweden fitting orthokeratology lenses and 5 of those stands for 75 % of all fittings. Measuring the intraocular pressure in the eye is an important part of an eye- examination, because high intraocular pressure can result in glaucomatous changes. When using the orthokeratology lenses the corneal thickness changes, it decreases in the central epithelium and increases in the midperipheral stroma. The corneal thickness is affecting the intraocular pressure value.

Aim: The aim of the study was to evaluate how the intraocular pressure, measured with a non-contact tonometer, changes when using orthokeratology lenses.

Method: 7 people were fitted with orthokeratology lenses. The intraocular pressure was measured before using the lenses, after the first night, after the third night and after the seventh night. 12 eyes were measured after the tenth night, because of drop- out of two eyes.

Result: Already after the first night a significant decrease in the intraocular pressure occurred with 1, 34 mm Hg (p= 0,049). Day ten the intraocular pressure had an average decrease of 2, 67 ± 2, 14 mm Hg, which was a significant change (p= 0, 002 ).

Discussion: This study shows when wearing orthokeratology lenses a decrease in 2, 67 ± 2, 14 mm Hg at day 10 can be expected.

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Chiu, Flora T. (Flora Tze Kwan). "An exploration of through-the-eye intraocular pressure measurement device." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/42118.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.
Includes bibliographical references (leaves 70-71).
Glaucoma, caused by an elevated intraocular pressure (IOP), is one of the leading causes of blindness. As constant monitoring of IOP is essential in the treatment of glaucoma, the IOP measurement techniques described in patents and patent applications since 1950 are examined. None of the methods provides a simple and comfortable approach for patients to self monitor their IOPs at different times throughout the day. A through-the-eyelid tonometry method is proposed to address the deficiencies of the previous techniques. Two through-the-eyelid tonometers are designed, and parts of the prototypes are built.
by Flora T. Chiu.
M.Eng.

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Nunes, Mariana Pinto. "Effects of methadone on intraocular pressure in dogs and cats." Master's thesis, Universidade de Lisboa, Faculdade de Medicina Veterinária, 2018. http://hdl.handle.net/10400.5/16470.

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Dissertação de Mestrado Integrado em Medicina Veterinária
Objective: The purpose of this study was to determine the effects of methadone as a solo-agent of anaesthetic premedication, on intraocular pressure (IOP) in dogs and cats undergoing both elective surgeries or diagnostic procedures. Methods: The study group was composed of 32 and 5 cats. The baseline IOP (T0) of the subjects were registered before IV methadone at the 0.2 mg kg-1 dosage. IOP variations were registered ten (T10) and twenty (T20) minutes after the drug administration. IOP values were measured with rebound tonometry (Icare ®, Helsinki, Finland), each animal being positioned in sternal recumbency, without e-collars and with the head maintained relaxed at the level of the thorax. All variables were compared at each specific time point using a repeated-measures analysis of variance (ANOVA) with R® 3.3.3 software and the R-Commander extension. The differences were considered significant when p < 0.05. Results: The study group was composed of 32 dogs with a mean age of 8,6 ± 3,3 years and 5 cats with a mean age of 6,02 ± 5,3 years. Ophthalmic exam was normal. The mean ± SD baseline (T0) and post-treatment (T10, T20) IOP values were respectively: 17,1 ± 3,32 mm Hg, 16,9 ± 3,37 mm Hg and 16,3 ± 3,33 mm Hg. In the majority of the individuals, IOP levels decreased less significantly at T10 comparing to the mean values at T20. There were no statistically significant differences between baseline values and post-treatment values (p=0.296). Conclusions: There were no statistically significant variations in IOP values in dogs and cats after the administration of methadone as a solo-agent of anaesthetic premedication. Methadone may be a good alternative as anaesthetic premedication in intraocular surgery or in sedation of glaucoma patients since it apparently does not interfere with IOP.
RESUMO - Objetivo: Este estudo teve como objetivo determinar os efeitos do uso de metadona como fármaco único de pré-medicação cirúrgica, na pressão intraocular, tanto em cães, como em gatos, submetidos a procedimentos cirúrgicos eletivos e/ou exames de diagnóstico complementares que necessitassem de sedação prévia. Métodos: O grupo em estudo incluiu cães e gatos submetidos a sedação. Os valores de pressão intraocular foram medidos antes da administração intravenosa de metadona, na dose de 0,2 mg kg-1, e após 10 minutos (T10) e 20 minutos (T20) da mesma. As medições foram efetuadas por tonometria de ressalto (Icare ®, Helsínquia, Finlândia) com o animal posicionado em decúbito ventral, sem uso de colar isabelino e com a cabeça mantida numa posição relaxada ao nível do tórax. Os valores da variável pressão intraocular, obtidos nos três tempos, foram comparados utilizando o teste de análise de variância (ANOVA) para medidas repetidas, com o auxílio do software R® 3.3.3 software e na sua extensão R-Commander. As diferenças foram consideradas significativas quando p< 0.05. Resultados: O grupo em estudo foi composto por 32 cães e 5 gatos com uma média de idades de 8,6 ± 3,3 e 6,02 ± 5,3 anos de idade, respetivamente. Os valores da média ± desvio padrão da pressão intraocular basais (T0) e após a administração de metadona (T10 e T20) foram, respetivamente: 17,1 ± 3,32 mm Hg, 16,9 ± 3,37 mm Hg e 16,3 ± 3,33 mm Hg. Na maioria dos indivíduos, os níveis de pressão intraocular diminuíram de forma menos marcada em T10 comparativamente com T20. Não se observou diferença estatisticamente significativa entre os três tempos em estudo (p=0,296). Conclusões: Não se observaram variações estatisticamente significativas na pressão intraocular em cães e gatos após a administração de metadona como fármaco único de pré-medicação. Este fármaco pode ser uma boa opção na cirurgia intraocular ou na sedação de animais com diagnóstico prévio de glaucoma, uma vez que aparentemente não interfere com a pressão intraocular.
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Irby, Alice L. "Social economic status association with intraocular pressure in rural Alabama." Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2009m/irby.pdf.

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Eklund, Anders. "Resonator sensor technique for medical use : An intraocular pressure measurement system." Doctoral thesis, Umeå University, Radiation Sciences, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1.

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In the work of this doctoral dissertation a new resonator sensor technique, first presented in 1989, has been further developed and evaluated with focus on technical characteristics and applications within the medical field.

In a first part a catheter-type tactile sensor using the resonator sensor technique was evaluated in a silicone model and applied to human prostate in vitro. The main finding was that different histological compositions of prostate tissue correlated with the frequency shift, .fS, of the resonator sensor and that the common property was the hardness of the tissue. The results indicated that hardness of the prostate tissue, and maybe hardness of human tissue in general, can be expressed according to a cone penetration standard (DIN ISO 2137) and that the hardness can be measured with this tactile sensor system. The tissue hardness application for the resonator sensor technique has to be further developed and evaluated in a larger study. The study also produced results that has led to the basic understanding of the resonator sensor system. One important result was that .fS of the sensor system was related to the contact area between sensor and sample. This indicated that the resonance sensor could be used for contact area measurement.

In a second part, containing three studies, the area-sensing capability from the first study was utilised in the development and evaluation of the applanation resonator sensor (ARS) for measurement of intraocular pressure (IOP). For the purpose of evaluating IOP-tonometers, an in vitro pig-eye model was developed, and it was shown that a saline column connected to the vitreous chamber could be used successfully to induce variations in IOP.

A ARS sensor with a flat contact surface was applied onto the cornea with constant force and .fS was measured. A mathematical model based on the Imbert-Fick law and the assumption that .fS was linearly related to contact area was proposed and verified with a convincing result. IOP measured with the ARS correlated well (r=0.92, n=360) with the IOP elicited by a saline column.

The ARS in a constant-force arrangement was evaluated on healthy human subjects in vivo. The results verified the sensor principle but revealed a nonnegligible source of error in off-centre positioning between the sensor and cornea. The sensor probe was redesigned and evaluated in the in vitro model. The new probe, with a spherical contact surface against the eye reduced the sensitivity to off-centre positioning. It was also shown that a .fS normalisation procedure could reduce the between-eye differences.

The ARS method for IOP measurement was further developed using combined continuous force and area measurement during the dynamic phase when the sensor initially contacts the cornea. A force sensor was included with the resonator sensor in one probe. Evaluation was performed with the in vitro pig-eye model. The hypothesis was that the IOP could be deduced from the differential change of force and area during that phase. The study showed good accuracy and good reproducibility with a correlation of r=0.994 (n=414) between measured pressure in the vitreous chamber and IOP according to the ARS. Measurement time was short, 77 ms after initial contact. Problems with inter-eye differences and low resolution at high pressures were reduced. The ARS method is the first to combine simultaneous, continuous sampling of both parameters included in the applanation principle. Consequently, there is a potential for reducing errors in the clinical IOP tonometry.

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Luce, Alexander Vallejo. "Design of Automated Digital Eye Palpation Exam for Intraocular Pressure Measurement." Thesis, The University of Arizona, 2009. http://hdl.handle.net/10150/192537.

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Chiu, Yee-hang Thomas. "Intraocular pressure, optic nerve fiber layer thickness and visual field in normotensive eyes with narrow drainage angle /." View the Table of Contents & Abstract, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37207994.

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Chiu, Yee-hang Thomas, and 趙懿行. "Intraocular pressure, optic nerve fiber layer thickness and visual field in normotensive eyes with narrow drainage angle." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B45011102.

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Laiquzzaman, Mohammad. "Inter-relations between eyeblinking, tear film and corneal health in older people." Thesis, Glasgow Caledonian University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322281.

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Pillai, Aditi. "Effects of Body Temperature and General Anesthetics on Intraocular Pressure in Rats." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7351.

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Ocular hypertension has been identified as the fundamental risk factor in glaucoma which is the leading cause for irreversible blindness in the world. Understanding the different factors that affect IOP is of utmost importance in clinical management as IOP is considered as the fundamental factor in assessing the efficiency of glaucoma medications. Several studies have attempted to assess factors that could affect IOP including age, body position, blood pressure, anesthetics commonly used during eye operations, etc. However, in most of these studies IOP is measured under anesthesia using rodent models and these anesthetics could affect the IOP measurements directly or indirectly. The use of tonometry in such experiments also includes certain limitations like acquiring IOP at discrete moments in time, human error while handling the instrument and stress induced spikes in IOP while handling awake animals. This study uses a wireless continuously monitoring device to eliminate these limitations while also acquiring IOP at a higher rate. Anesthesia induction is known to lower body temperature. However, previous studies on the effects of various anesthetic agents fail to take into account this drop in body temperature which could potentially lead to erroneous results. This thesis focuses on studying the effects of two commonly used anesthetic agents, isoflurane and ketamine while accounting for loss in body temperature. The effects of changing body temperature on intraocular pressure was also studied to help understand the effects of these factors accurately. There was a statistically significant drop (p<0.001) in intraocular pressure post isoflurane induction with no heat support across several animals. The addition of heat support in the next set of experiments resulted in an almost steady pressure throughout the experiment. Since the body temperature was maintained constant throughout the experiment, there was no statistically significant difference (p>0.05) among IOP’s for the awake and anesthetized condition. This conclusion was then confirmed by obtaining a direct effect of changing body temperature on IOP. There was a rise in IOP while the animal was placed on a 42 degree Celsius heating pad and a drop in IOP while the animal was placed on a 20 degree Celsius surface with no heat support. The corresponding changes in body temperature were confirmed using a rectal thermometer. There were no significant changes in the IOP measured by the sensor while measuring pressure with the iCare tonolab. Applanation tonometry however produced an average mean intraocular pressure increase of 2.11 ± 1.62 mmHg.

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Hamilton, Kirsten School of Optometry &amp vVsion Science UNSW. "Corneal hydration and the accuracy of Goldmann tonometry." Awarded by:University of New South Wales. School of Optometry and vVsion Science, 2006. http://handle.unsw.edu.au/1959.4/30468.

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The purpose of this thesis was to investigate the effect of corneal swelling on the accuracy of Goldmann tonometry estimates of intraocular pressure (IOP). In the first experiment, central corneal thickness (CCT, ultrasonic pachymetry), IOP (Goldmann tonometry) and corneal curvature (keratometry) was measured in one eye of 25 subjects every two hours for 24 hours, except for 8 hours overnight (no measurements taken), and for the first two hours after awakening (measurement frequency 20 minutes). CCT (+20.1??10.9 pm) and IOP (+3.1??2.4 mmHg) peaked on eye opening, and then decreased at a similar rate (r=0.967, p<0.001) for the next two hours. Corneal swelling may have influenced the accuracy of Goldmann IOP measurements during this time. In the second and third studies, the CCT, IOP and corneal curvature were measured in both eyes of two groups of 25 subjects before and after the induction of corneal swelling, resulting from two hours of monocular closed eye contact lens wear. The increase in IOP was correlated to the increase in CCT at a rate of 0.33 to 0.48 mmHg per 10 pm, which signified an overestimation error in Goldmann IOP measurement. However, the change in IOP could not be accounted for solely by the change in CCT. In the fourth study, CCT, IOP and corneal curvature were used in conjunction with the Orssengo-Pye algorithm to determine the range of Young's modulus in the normal population, which was 0.29??0.06 MPa. Physiological variations in Young's modulus had a similar effect on Goldmann tonometry to CCT. In the fifth study, the data collected for studies 2 and 3 was used to calculate the Young's modulus changes associated with corneal swelling, again with the assistance of the Orssengo-Pye algorithm. No systematic change in Young's modulus was recorded after contact lens wear, but the model suggested that corneal biomechanical changes were responsible for the remainder of the change in IOP. All experimental results were combined to develop a model to calculate the diurnal variation of Goldmann IOP errors. The likely error in IOP due to overnight corneal swelling was 0.6 to 1.4 mmHg, which may explain as much as 45% (1.4 mmHg) of the 3.1 mmHg diurnal variation of IOP. In summary, small amounts of corneal swelling were shown to have a clinically significant impact on the accuracy of Goldmann tonometry. This may interfere with the measurement of the diurnal variation of IOP, particularly if measurements are taken prior to the resolution of overnight corneal swelling.

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McCafferty, Sean, Garrett Lim, William Duncan, Eniko Enikov, and Jim Schwiegerling. "Goldmann Tonometer Prism with an Optimized Error Correcting Applanation Surface." ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2016. http://hdl.handle.net/10150/622594.

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Purpose: We evaluate solutions for an applanating surface modification to the Goldmann tonometer prism, which substantially negates the errors due to patient variability in biomechanics. Methods: A modified Goldmann or correcting applanation tonometry surface (CATS) prism is presented which was optimized to minimize the intraocular pressure (lOP) error due to corneal thickness, stiffness, curvature, and tear film. Mathematical modeling with finite element analysis (FEA) and manometric lOP referenced cadaver eyes were used to optimize and validate the design. Results: Mathematical modeling of the optimized CATS prism indicates an approximate 50% reduction in each of the corneal biomechanical and tear film errors. Manometric lOP referenced pressure in cadaveric eyes demonstrates substantial equivalence to GAT in nominal eyes with the CATS prism as predicted by modeling theory. Conclusion: A CATS modified Goldmann prism is theoretically able to significantly improve the accuracy of lOP measurement without changing Goldmann measurement technique or interpretation. Clinical validation is needed but the analysis indicates a reduction in CCT error alone to less than +/- 2 mm Hg using the CATS prism in 100% of a standard population compared to only 54% less than +/- 2 mm Hg error with the present Goldmann prism. Translational Relevance: This article presents an easily adopted novel approach and critical design parameters to improve the accuracy of a Goldmann applanating tonometer.

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Borges, Alessandra Gonçalves. "Efeito do cloridrato de dorzolamida a 2%, maleato de timol a 0,5% e associação de ambos na pressão intra-ocular : estudo experimental em cães /." Botucatu : [s.n.], 2004. http://hdl.handle.net/11449/89128.

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Orientador: Cláudia Valéria Seullner Brandão
Resumo: Dentre as doenças oculares diagnosticadas no cão, o glaucoma reveste-se de singular importância, como afecção potencial causadora de cegueira. O aumento da pressão intra-ocular (PIO) é o fator de risco primário para o desenvolvimento da neuropatia óptica glaucomatosa canina. A dorzolamida e o timolol, fármacos utilizados para o tratamento do glaucoma, reduzem a PIO pela diminuição da produção do humor aquoso, embora utilizem diferentes mecanismos de ação. O objetivo do trabalho foi avaliar o efeito do cloridrato de dorzolamida 2%, maleato de timolol 0,5% e da combinação de ambos na pressão intra-ocular de cães normais e verificar possíveis alterações na PIO do olho contra-lateral sem tratamento. Foram utilizados 60 cães, distribuídos em três grupos (G) aleatórios de 20 animais. Cada grupo recebeu tratamento tópico no olho esquerdo com timolol 0,5% (GT), dorzolamida 2% (GD) ou a combinação, timolol 0,5% e dorzolamida 2% (GTD). Em todos os grupos, a mensuração da PIO foi realizada utilizando-se tonômetro de aplanação (Tonopen). As medidas foram realizadas, em ambos os olhos, uma hora antes e uma, duas, quatro, seis e oito horas após a instilação de uma gota do colírio no olho esquerdo. No olho tratado percentual de redução máxima da associação timolol/dorzolamida foi numericamente superior (27%) comparado ao timolol (21,9%) e dorzolamida (22,4%) quando utilizados como monoterapia. O olho não tratado apresentou uma redução significativa da PIO, sendo que a redução máxima para o GT foi de 7%, para o GD de 13,8% e para o GTD de 13,6%. A dorzolamida e a associação timolol/dorzolamida promoveram uma ação redutora maior, após uma e seis horas da sua instilação no olho tratado. A administração tópica do timolol 0,5%, dorzolamida a 2% como monoterapia e a associação fixa destes fármacos resultou na redução significativa da PIO de cães clinicamente normais.
Abstract: Glaucoma is one of the most important ocular diseases in the dog. Increased intraocular pressure (IOP) is the major risk factor for the development of glaucoma. Dorzolamide and timolol are drugs used for the treatment of glaucoma. Both drugs modify aqueous humor outflow by different mechanisms, resulting in decreased IOP. The aim of this work was to evaluate the efficacy of dorzolamide hydrochloride, timolol maleate and the combination of both drugs on IOP of healthy dogs. Sixty adult dogs were randomly and equally assigned to three groups (n = 20 per group). Each group received topical treatment in the left eye with 0,5% timolol, 2% dorzolamide or the combination (0,5% timolol / 2% dorzolamide). IOP measurements were made using aplanation tonometry (Tono-pen) after local instillation of 0,5% proparacaine in he both eyes. Measurements were performed 1 hour before (baseline) instillation of a single drop of the test drugs in the left eye, and at 1, 2, 4, 6 and 8 hours after treatment. Similar measurements were also performed in the right eye (nontreated eye). In the nontreated eye, IOP decreased over time, with a maximum decrease from baseline of 7%, 13,8% and 13,6% in the timolol, dorzolamide e timolol/dorzolamide groups, respectively. In the treated eye, there was a greater reduction in IOP for the combination (27% maximum decrease from baseline) when compared with timolol (21,9%) and dorzolamide (22,4%) groups. Dorzolamide and timolol/dorzolamide caused greater decreases in IOP at 1 and 6 hours after drug instillation. It was concluded that 0,5% timolol, 2% dorzolamide and the combination of these drugs are effective in reducing IOP in healthy dogs.
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Hedman, Katarina. "Pooling Data from Similar Randomized Clinical Trials Comparing Latanoprost with Timolol; Medical Results and Statistical Aspects." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3392.

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Pereira, Fabiana Quartiero. "Comparação entre o tonômetro de rebote (Tonovet) e o novo tonômetro de aplanação (Tono-pen a via) durante curva diurna da pressão intraocular de coelhos adultos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/27277.

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A determinação da pressão intraocular (PIO) é fundamental no exame oftálmico. Atualmente, novos tonômetros, baseados em diferentes princípios, estão sendo continuamente desenvolvidos. O objetivo deste estudo foi estabelecer os valores de referência da PIO de coelhos adultos, sem efeito de tranquilizantes, mensurada com o tonômetro de rebote (Tonovet) e o de aplanação (Tono-Pen Avia). Também foi preconizada a mensuração da PIO ao longo do dia nesta espécie e a comparação dos resultados obtidos com os dois tonômetros. A PIO foi aferida ao longo do dia (6h, 9h, 12h, 15h e 18h) em 38 coelhos (76 olhos) da raça Nova Zelândia Branca, adultos, com idade média de seis meses, machos ou fêmeas, com massa corporal média de 3,5kg. Previamente, foi realizado teste da lágrima de Schirmer, prova da fluoresceína, biomicroscopia com lâmpada de fenda e oftalmoscopia direta em todos os animais. A tonometria de rebote foi realizada primeiro e, decorridos 10 minutos, foi instilado colírio anestésico e realizada a tonometria de aplanação. A PIO obtida utilizando as duas técnicas foi comparada estatisticamente. A média da PIO com o Tonovet foi de 9,51 ± 2,62 mmHg (variação de 3- 23mmHg) e 15,44 ± 2,16 mmHg (variação de 8 – 26mmHg) com o Tono-Pen Avia. Houve diferença estatística significante entre os valores obtidos com os dois tonômetros (P < 0,001). A relação entre os dois tonômetros foi representada através da equação de regressão linear: y = 0,4923x + 10,754 (y= Tonovet e x= Tono-Pen Avia). No início do dia foram registradas PIOs mais elevadas, mas a média dos valores ao longo do dia, com ambos os aparelhos, foi estatisticamente o mesmo (p = 0,086). O valor do coeficiente de correlação obtido foi r2= 0,357. Os resultados demonstram que o Tono-Pen Avia é mais variável e superestima a PIO de coelhos quando comparado ao Tonovet. Nas primeiras horas do dia, a PIO de coelhos foi mais alta que nos demais horários, independentemente do tonômetro utilizado.
The determination of intraocular pressure (IOP) is crucial in eye examination. Currently, new tonometers based on different principles are being continuously developed. The objective was to establish reference values of IOP of adults rabbits without the effect of tranquilizers, utilizing the rebound tonometer (Tonovet ) and the applanation tonometer (Tono-Pen Avia) for measurements. It also aimed to advocate the measurement of IOP throughout the day in this species and compare the results obtained with the two tonometers. The IOP was measured throughout the day (6h, 9h, 12h, 15h and 18h) in 38 New Zealand White rabbits (76 eyes), adults, males or females, with mean weight of 3.5kg and an average age of six months. Previously, the Schirmer tear test, fluorescein test, biomicroscopy with slit lamp and direct ophthalmoscopy were performed in all animals. First, the rebound tonometry was performed and after a minimum of 10 minutes anesthetic drops were instilled and applanation tonometry was carried out. IOP obtained using the two techniques was compared by statistical analysis. The average IOP was 9.51 ± 2.62 mmHg (range 3 - 23 mmHg) and 15.44 ± 2.16 mmHg (range 8 – 26mmHg), with Tonovet and Tono-Pen Avia, respectively. Statistic significant difference between the two tonometers was (P <0.001). The linear regression equation that describes the relationship between the two tonometers was: y = 0.4923 x + 10.754 (y= Tonovet e x= Tono-Pen Avia). Earlier in the day, higher IOPs were recorded, but the average behavior of IOP throughout the day with both devices was statistically the same (p = 0.086). The value of the correlation coefficient was r2 = 0.357. The results show that the Tono-Pen Avia is more variable and overestimates the IOP of rabbits when compared with the Tonovet. In the early hours, the IOP of rabbits was higher than at other times, regardless of the tonometer used.

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Claros, Chacaltana Flor Diana Yokoay. "Avaliação da pressão intraocular em chinchilas (chinchilla Lanigera) de diferentes faixas etárias utilizando tonometria de rebote." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2013. http://hdl.handle.net/10183/76540.

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A aferição da pressão intraocular (PIO) é fundamental durante o exame oftálmico. Objetivou-se estabelecer os valores de referência da PIO de chinchilas de diferentes faixas etárias utilizando o tonômetro de rebote. A PIO foi aferida ao longo do dia às 7, 12 e 19 horas utilizando o tonômetro de rebote (Tonovet®). As chinchilas foram subdivididas em três grupos com 12 animais cada, considerando as idades, designados por GI (animais com idade entre dois a seis meses), GII (com idade entre 20 e 34 meses) e GIII (animais com idade entre 37 e 135 meses). Previamente, foram realizados teste da lágrima de Schirmer, prova da fluoresceína, biomicroscopia com lâmpada de fenda e oftalmoscopia indireta em todos os animais. O valor médio da pressão intraocular encontrado foi 2,49 ± 0,56 mmHg, os valores médios para o grupo I foi de 2,47±0,581 mmHg, no grupo II de 2,47±0,581 mmHg e no grupo III de 2,51±0,531 mmHg. Não foram encontradas diferenças significativas entre a idade e a PIO (P = 0,756). Não foram encontradas diferenças significativas entre as horas do dia e a PIO (P = 0,415). Não foram encontradas diferenças significativas entre os sexos (P = 0,857). Os valores da PIO em chinchilas não sofrem alterações decorrentes do sexo e da idade dos animais. Não ocorre influência do ritmo circadiano na PIO de chinchilas.
The assessment of intraocular pressure (IOP) is essential for the ocular examination. The purpose of this study was to establish reference values of intraocular pressure chinchillas (Chinchilla lanigera) of different age groups. Thirty-six Chinchillas were divided in three groups of 12 animals each, considering the ages designated by GI (animals aged two to six months), GII (aged between 20 and 34 months) and GIII (animals aged between 37 and 135 months). Intraocular pressure was measured at 7, 12 and 19 hours. Tear production was measured, fluorescein test, slit-lamp biomicroscopy and indirect ophthalmoscopy in all animals and IOP was measured using the rebound tonometer (Tono Vet®) set on the P (undefined species) setting, with measurements obtained from each eye. No abnormalities were found on ophthalmic examination. The mean (±SD) of IOP was 2.49 ± 0.56 mmHg, with a range of 2-4 mmHg. The mean (±SD) of IOP for group I, II and III were 2.47 ± 0.581 mmHg, 2.47 ± 0.581 mmHg and 2,51 ± 0.531 mmHg, respectively. No significant differences were found between age and IOP and no significant differences were found between the hours of day and IOP. No significant differences were found between the genders. The IOP in chinchillas is unchanged between genders and age of the animals. The circadian rhythm is not influenced by IOP in chinchillas.

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Liu, M. "Characterization of dendritic changes induced by elevated intraocular pressure in a chronic glaucoma model." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1306761/.

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Visual information is sent from the retina to central visual targets through the optic nerve which is formed of retinal ganglion cells’ (RGCs) axons. In rodents, the superior colliculus (SC) is the major site of termination of retinal axons and the lateral geniculate nucleus (LGN) is another target of retinal axons. Glaucoma is a progressive optic neuropathy, characterized by RGC death. Dendrites are fine neuronal processes which support postsynaptic contact elements and are responsible for receiving synaptic signals. Accordingly, the morphology of dendrites has a profound impact on integrating neuronal input to the central nervous system from peripheral targets. Previous studies have documented dendritic changes in neuronal degenerative processes including those occurring in ageing and diseases. However, the morphological changes of dendrites in the visual pathway in glaucoma have not been well characterized. This thesis characterizes morphological changes of dendrites in the retina and the central visual targets in an experimental rat model of glaucoma for the first time. Dendritic labelling was achieved using the fluorescent dye DiI with in vivo and in vitro techniques. Dendrites of neurons in the SC and LGN were labelled in vitro using 0.1% DiI solution, and those of the RGCs were labelled using the biolistic technique. Confocal microscopy was next performed to image neurons, and dendrites were traced and quantified using Image J. Dendritic parameters including the mean dendritic length and the number of dendrites per neuron were analyzed in baseline, glaucoma animals and age-matched controls. Dendritic morphologies were studied in five types of neurons in the SC (including horizontal (H); piriform (P); narrow field vertical (V); wide field vertical (W) and stellate (S) cells), two types of neurons in the LGN (including the relay neuron type I (LG1) and type II (LG2)) and three types of RGCs (including type I (RI), type II (RII) and type III (RIII)). In this thesis, both age-related and glaucoma-related dendritic changes were demonstrated in the RGCs, SC cells and LGN cells in our rat model of experimental glaucoma. Firstly, the mean dendritic length and dendritic number of RGCs, SC cells and LGN cells were significantly reduced during ageing in normal animals, and more pronounced changes were observed in glaucoma animals. Secondly, significant dendritic shrinkage and losses were also shown in glaucoma animals compared with age-matched controls. Thirdly, the RGC was the first site to show dendritic changes following elevated IOP, but the most prominent changes were visible in the SC. The results in this study implicated that both the RGC and SC are potential sites for an early diagnosis strategy. Additionally, the glaucoma-related dendritic degeneration was demonstrated not only in the RGCs, but also in the SC and LGN, indicating that both the retina and the brain should be targeted when considering therapies for glaucoma. In conclusion, this thesis characterizes dendritic changes in the visual pathway in rats with chronic glaucoma, demonstrating that both ageing and elevated intraocular pressure (IOP) can affect dendritic morphology in the RGCs, SC cells and LGN cells. The findings in this study have contributed to the understanding of retinal and central neuronal degeneration in glaucoma, providing new insights into potential diagnosis and therapeutic strategies.

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Harju, Mika. "Exfoliation glaucoma : studies on intraocular pressure, optic nerve head morphometry, and ocular blood flow." Helsinki : University of Helsinki, 2001. http://ethesis.helsinki.fi/julkaisut/laa/kliin/vk/harju/.

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Renzo, Roberta [UNESP]. "Pressão intra-ocular, condições endoteliais e prostaglandina E2 no humor aquoso de cães com catarata senil madura ou hipermatura." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/88973.

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Made available in DSpace on 2014-06-11T19:23:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-16Bitstream added on 2014-06-13T20:50:54Z : No. of bitstreams: 1 renzo_r_me_jabo.pdf: 301706 bytes, checksum: 7ba09919044057e80244fe4b39f2b41e (MD5)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Estudaram-se a pressão intraocular, a densidade e a hexagonalidade de células endoteliais, níveis de Prostaglandina E2 e sua correlação com catarata senil madura (n=8) ou hipermatura (n=8). Adicionalmente, foram utilizados valores de Prostaglandina E2 do humor aquoso de cães oftalmologicamente saudáveis (n=7). Para avaliação da pressão intraocular empregou-se tonometria digital de aplanação. A avaliação da densidade e da hexagonalidade das células endoteliais foi realizada por meio de microscopia especular de não contato. Sob anestesia geral, 0,2mL de humor aquoso foram colhidos por meio de paracentese da câmara anterior. As amostras de aquoso foram congeladas e armazenadas à -80 oC para mensuração da concentração de PGE2, por imunoensaio enzimático competitivo. Os valores foram comparados estatisticamente, empregando-se análise de variância de via única, e o teste de múltiplas comparações de Bonferroni. Teste t não pareado foi utilizado para se avaliar os dados obtidos por microscopia especular. Possíveis correlações entre os resultados foram comparadas aplicando-se o teste de Person. Adotou-se nível de significância de p<0,05. Em ambos os grupos observou-se diminuição significativa da pressão intraocular (PIO), entretanto não houve diferença entre eles (p = 0,90). As médias dos valores de densidade celular (CD) e de hexagonalidade (HEX) foram 2253,363 cell/mm² e 59,03% para GSM e 2058,325 cell/mm² e 63,75% para GSH, respectivamente. Entretanto não houve diferença significativa entre ambos, tanto para CD (p=0,201), quanto para HEX (p=0,61). Observou-se incremento nos valores de PGE2 nos grupos com catarata em relação aos cães oftalmologicamente saudáveis (p<0,001), entretanto, não houve diferença significativa entre os grupos com catarata...
Intraocular pressure, endothelial cell density and hexagonality, and aqueous humor prostaglandin E2 (PGE2) were studied and correlated in dogs with mature (n=8) and hypermature (n=8) senil cataratcs. In addition, aqueous humor PGE2 values of ophthalmic healthy dogs (n=7) were used. Non contact specular microscopy was used to evaluate density and hexagonality of endothelial cells. 0.2mL of aqueous humor was collected by means of anterior chamber paracentesis. Aqueous humor samples were frozen at -80 oC and concentration of PGE2 were quantified by means of competitive enzyme immunoassay. PGE2 values were statistically compared with one way analysis of variance and Bonferroni´s multi comparison test. Specular microscopy data were assessed by means of unparied T test. Person´s test was used in order to assess possible correlations among data. Significance was set at value of P < 0.05. Values of endothelial cell density and hexagonality did not change significantly between groups (P = 0.61). PGE2 values were significantly higher in dogs with cataract, when compared with ophthalmic healthy dogs (P < 0.001), however, this parameter did not change significantly between mature and hypermature groups (P > 0.05). Is it possible tosay that cataract patients in stages of maturity or hipermaturity develop uveitis... (Complete abstract click electronic access below)

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Borges, Alessandra Gonçalves [UNESP]. "Efeito do cloridrato de dorzolamida a 2%, maleato de timol a 0,5% e associação de ambos na pressão intra-ocular: estudo experimental em cães." Universidade Estadual Paulista (UNESP), 2004. http://hdl.handle.net/11449/89128.

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Made available in DSpace on 2014-06-11T19:23:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2004Bitstream added on 2014-06-13T19:30:13Z : No. of bitstreams: 1 borges_ag_me_botfmvz.pdf: 619936 bytes, checksum: 26f3dbd1632fca5d2ec5d73fee61d030 (MD5)
Dentre as doenças oculares diagnosticadas no cão, o glaucoma reveste-se de singular importância, como afecção potencial causadora de cegueira. O aumento da pressão intra-ocular (PIO) é o fator de risco primário para o desenvolvimento da neuropatia óptica glaucomatosa canina. A dorzolamida e o timolol, fármacos utilizados para o tratamento do glaucoma, reduzem a PIO pela diminuição da produção do humor aquoso, embora utilizem diferentes mecanismos de ação. O objetivo do trabalho foi avaliar o efeito do cloridrato de dorzolamida 2%, maleato de timolol 0,5% e da combinação de ambos na pressão intra-ocular de cães normais e verificar possíveis alterações na PIO do olho contra-lateral sem tratamento. Foram utilizados 60 cães, distribuídos em três grupos (G) aleatórios de 20 animais. Cada grupo recebeu tratamento tópico no olho esquerdo com timolol 0,5% (GT), dorzolamida 2% (GD) ou a combinação, timolol 0,5% e dorzolamida 2% (GTD). Em todos os grupos, a mensuração da PIO foi realizada utilizando-se tonômetro de aplanação (Tonopen). As medidas foram realizadas, em ambos os olhos, uma hora antes e uma, duas, quatro, seis e oito horas após a instilação de uma gota do colírio no olho esquerdo. No olho tratado percentual de redução máxima da associação timolol/dorzolamida foi numericamente superior (27%) comparado ao timolol (21,9%) e dorzolamida (22,4%) quando utilizados como monoterapia. O olho não tratado apresentou uma redução significativa da PIO, sendo que a redução máxima para o GT foi de 7%, para o GD de 13,8% e para o GTD de 13,6%. A dorzolamida e a associação timolol/dorzolamida promoveram uma ação redutora maior, após uma e seis horas da sua instilação no olho tratado. A administração tópica do timolol 0,5%, dorzolamida a 2% como monoterapia e a associação fixa destes fármacos resultou na redução significativa da PIO de cães clinicamente normais.
Glaucoma is one of the most important ocular diseases in the dog. Increased intraocular pressure (IOP) is the major risk factor for the development of glaucoma. Dorzolamide and timolol are drugs used for the treatment of glaucoma. Both drugs modify aqueous humor outflow by different mechanisms, resulting in decreased IOP. The aim of this work was to evaluate the efficacy of dorzolamide hydrochloride, timolol maleate and the combination of both drugs on IOP of healthy dogs. Sixty adult dogs were randomly and equally assigned to three groups (n = 20 per group). Each group received topical treatment in the left eye with 0,5% timolol, 2% dorzolamide or the combination (0,5% timolol / 2% dorzolamide). IOP measurements were made using aplanation tonometry (Tono-pen) after local instillation of 0,5% proparacaine in he both eyes. Measurements were performed 1 hour before (baseline) instillation of a single drop of the test drugs in the left eye, and at 1, 2, 4, 6 and 8 hours after treatment. Similar measurements were also performed in the right eye (nontreated eye). In the nontreated eye, IOP decreased over time, with a maximum decrease from baseline of 7%, 13,8% and 13,6% in the timolol, dorzolamide e timolol/dorzolamide groups, respectively. In the treated eye, there was a greater reduction in IOP for the combination (27% maximum decrease from baseline) when compared with timolol (21,9%) and dorzolamide (22,4%) groups. Dorzolamide and timolol/dorzolamide caused greater decreases in IOP at 1 and 6 hours after drug instillation. It was concluded that 0,5% timolol, 2% dorzolamide and the combination of these drugs are effective in reducing IOP in healthy dogs.

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Kusne, Yael, Paul Kang, and Robert Fintelmann. "A retrospective analysis of intraocular pressure changes after cataract surgery with the use of prednisolone acetate 1% versus difluprednate 0.05%." DOVE MEDICAL PRESS LTD, 2016. http://hdl.handle.net/10150/622602.

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Purpose: To compare the effect of topical prednisolone acetate 1% (PA) used after routine cataract surgery to the effect of difluprednate 0.05% (DFBA) used for the same indication on intraocular pressure (IOP). Methods: An electronic query was created to gather information from all cataract surgeries between January 2010 and January 2015 within the electronic health record database at Barnet Dulaney Perkins, a multicenter, multiphysician private practice in Phoenix, Arizona. Information collected included age, sex, diabetes status, glaucoma history, medication regimen (use of PA or DFBA), and IOP before surgery, 5-10 days postoperatively (TP1) and 3-6 weeks postoperatively (TP2). Postoperative IOP measurements were compared to baseline IOP measurement in each patient. Results: Regardless of steroid used, all patients in this study experienced an increase in IOP within TP1 and returned to baseline IOP (+/- 2.0 mmHg) by TP2. Patients who received DFBA showed a statistically significant increase in IOP at TP1 compared to those on PA (P<0.001) with the mean IOP an average 0.60 mmHg higher (95% CI = 0.3, 0.9). The odds ratio of a clinically significantly increased IOP at TP1 (defined as overall IOP >= 21 mmHg and an increase of >= 10 mmHg) in DFBA-treated patients was 1.84 (95% CI = 1.4, 2.6). In patients treated with PA, 3% reached a significantly increased IOP, compared to 4.4% of patients in the DFBA group (P<0.05). Risk factors for increased IOP were identified, and include advanced age (>75) (P<0.005) and a history of glaucoma (P<0.001). Conclusion: In postoperative cataract patients, use of DFBA increased the risk of a clinically significant IOP increase.

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Åström, Siv. "Long-term follow-up of pseudoexfoliation, intraocular pressure and glaucoma : epidemiological studies in northern Sweden." Doctoral thesis, Umeå universitet, Oftalmiatrik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-64301.

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Purpose An age-cohort was studied with long-term follow-up. The population was born in 1915, living in the municipality of Skellefteå in 1981. The purpose was to investigate the prevalence and incidence of pseudoexfoliation (PEX), its influence on intraocular pressure (IOP) and development of open-angle glaucoma (OAG). Another purpose was to estimate the value of screening for glaucoma by comparing the screened group within the cohort with the remaining unscreened group. Methods In 1981, 339 (40%) of the 856 individuals in the cohort underwent an eye examination. This screened group was re-examined at seven-year intervals until 2002. At each visit the presence of PEX was registered, IOP was measured and the presence of glaucoma was assessed. After the 21-year follow-up period, glaucoma cases were also searched for in the medical records of the remaining unscreened individuals in the cohort. Proportions of glaucoma were compared between the two groups. Results The prevalence of PEX was 23% (95% confidence interval (CI): 20-26%) at the age of 66 and increased to 61% (CI: 50-71%) at the age of 87. The annual incidence of PEX was 1.8% (CI: 1.3-2.4%). The prevalence of OAG increased from 2.1% (CI: 0.8-4.3%) at the age of 66 years to 25 % (CI: 16-35%) at 87 years. The overall annual incidence of OAG was 0.9% (CI: 0.6-1.3%) and for OAG with PEX 2.1% (CI: 1.2-3.3%). PEX increased the risk of developing glaucoma at least four-fold. The incidence of diagnosed OAG in women was higher in the screened group than in the unscreened group (incidence rate ratio (IRR)=1.94, p=0.035). A corresponding difference could not be verified for men (p=0.58). The mean, agedependent, increase in IOP during the 21-year observation period was 0.05 mmHg/year. Conclusion The prevalence of PEX in this study population was the highest reported, and it increased with age. The presence of PEX increased the risk of developing OAG four times. In this study a higher proportion of OAG was revealed by screening among women but not among men. The age-related IOP increase was clinically insignificant.

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McCafferty, Sean, Jason Levine, Jim Schwiegerling, and Eniko T. Enikov. "Goldmann applanation tonometry error relative to true intracameral intraocular pressure in vitro and in vivo." BIOMED CENTRAL LTD, 2017. http://hdl.handle.net/10150/626266.

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Background: Goldmann applanation tonometry (GAT) error relative to intracameral intraocular pressure (IOP) has not been examined comparatively in both human cadaver eyes and in live human eyes. Futhermore, correlations to biomechanical corneal properties and positional changes have not been examined directly to intracameral IOP and GAT IOP. Methods: Intracameral IOP was measured via pressure transducer on fifty-eight (58) eyes undergoing cataract surgery and the IOP was modulated manometrically on each patient alternately to 10, 20, and 40 mmHg. IOP was measured using a Perkins tonometer in the supine position on 58 eyes and upright on a subset of 8 eyes. Twenty one (21) fresh human cadaver globes were Intracamerally IOP adjusted and measured via pressure transducer. Intracameral IOP ranged between 5 and 60 mmHg. IOP was measured in the upright position with a Goldmann Applanation Tonometer (GAT) and supine position with a Perkins tonometer. Central corneal thickness (CCT) was also measured. Results: The Goldmann-type tonometer error measured on live human eyes was 5.2 +/- 1.6 mmHg lower than intracameral IOP in the upright position and 7.9 +/- 2.3 mmHg lower in the supine position (p <.05). CCT also indicated a sloped correlation to error (correlation coeff. = 0.18). Cadaver eye IOP measurements were 3.1+/-2. 5 mmHg lower than intracameral IOP in the upright position and 5.4+/- 3.1 mmHg in the supine position (p <.05). Conclusion: Goldmann IOP measures significantly lower than true intracameral IOP by approximately 3 mmHg in vitro and 5 mmHg in vivo. The Goldmann IOP error is increased an additional 2.8 mmHg lower in the supine position. CCT appears to significantly affect the error by up to 4 mmHg over the sample size.

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Robinson, Christa Lee. "Evaluation of efficacy and biocompatibility of indirect intraocular pressure monitoring using a telemetric scleral sensor." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1274142444.

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Kim, Bongsu. "Multidisciplinary Engineered Approaches to Investigate Human Trabecular Meshwork Endothelial Cells in Regulation of Intraocular Pressure." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1307640155.

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Kotikoski, Hanna. "Effects of nitric oxide donors and cyclic GMP on intraocular pressure and aqueous humor dynamics." Helsinki : University of Helsinki, 2003. http://ethesis.helsinki.fi/julkaisut/laa/biola/vk/kotikoski/.

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Vitish-Sharma, Parveen. "The effect of Trendelenburg positioning in laparoscopic colorectal surgery on intraocular pressure and cognitive function." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/48966/.

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Trendelenburg positioning is frequently used during laparoscopic surgery particularly when access to the pelvis is required. With improvements in laparoscopic skills, high risk patients and more complex procedures are now frequently being performed laparoscopically. (Improvement, 2016) The aim of this thesis is to investigate the effect of Trendelenburg positioning on intraocular pressure (IOP) and cognitive function. Chapters 2 and 4 look at the effect of Trendelenburg positioning on IOP. Perioperative vision loss occurs rarely but it is a life changing complication. A rise in IOP is a recognised risk factor for POVL. The incidence of POVL following laparoscopic colorectal surgery has been quoted as 1.24 in 10,000 cases. (Pinkney et al., 2012) Chapter 2 is an observational study during which IOP was monitored during laparoscopic colorectal surgery. This was correlated with the degree of Trendelenburg tilt used during surgery. This study revealed an increase in IOP occurred which was dependent on the degree of Trendelenburg tilt as well as the time spent in this position (Pearson’s correlation coefficient was 0.78). Patients undergoing left-sided colonic resections had a mean maximum IOP rise of 15.2mmHg. Chapter 4 is a follow-on study which looked at acetazolamide as a method of reducing the IOP rise that occurred whilst in the Trendelenburg position. This was a randomised placebo controlled cross-over healthy volunteer study. After 4 hours of Trendelenburg, the mean IOP increase was 3.17mmHg in the placebo group compared to 0.02mmHg in the acetazolamide group (P < 0.05). This suggests acetazolamide has a role in reducing the IOP rise that occurs from Trendelenburg positioning. The second half of this thesis focuses on the effect of Trendelenburg positioning on cognitive function. Post-operative cognitive decline (POCD) is defined as cognitive impairment following surgical intervention. It is associated with increased hospital stay, longer return to work/normal functioning, and in patients with existing cognitive impairment a further decline can result in loss of ability to carry out activities of daily living. (Moller et al., 1998) Chapter 5 is an observational study that explores the incidence of short- or long-term POCD following laparoscopic colorectal surgery. Post-resectional surgery, 55.4% of patients had evidence of POCD on Day 1 and 31.6% at long-term follow-up. On Day 2, 11.6% had POCD following right-sided resection compared to 16.3% in the left-sided resection group. Chapter 6 and 7 look at the effect of Trendelenburg positioning on cognitive function in healthy volunteers. Chapter 6 assessed changes in brain function using magnetoencephalography and n-back testing as well as looking at MRI structural changes after 2 hours in Trendelenburg position. Although the difference was not statistically significant, there was an increase in brain volume after 2 hours in Trendelenburg compared to pre-Trendelenburg MRI scan suggesting an element of cerebral oedema. Chapter 7 was a volunteer study designed to assess the effect of time spent in Trendelenburg position on cognitive function using cognitive tests (n back, stroop and lexical decision making tasks). This was carried out at regular intervals whilst in the Trendelenburg position and again once the volunteer was placed supine. After 3 hours in the Trendelenburg position, 40% had cognitive decline compared to 26.7% after 30 minutes.

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Friström, Björn. "Aspects of the diagnosis and treatment of glaucoma /." Linköping : Univ, 2001. http://www.bibl.liu.se/liupubl/disp/disp2001/med690s.pdf.

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Chou, Tsung-Han. "Age-Related Structural and Functional Changes of the Mouse Eye: Role of Intraocular Pressure and Genotype." Scholarly Repository, 2011. http://scholarlyrepository.miami.edu/oa_dissertations/532.

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The murine eye naturally undergoes post-natal changes in eye size. This dissertation quantifies longitudinal structural and functional changes in control mice (C57BL/6J (B6), D2-Gpnmb+/SjJ) and in DBA/2J (D2) mice, which spontaneously develop elevated intraocular pressure (IOP). IOP elevation results in abnormal eye elongation, retinal nerve fiber layer (RNFL) thickness thinning and retinal ganglion cell (RGC) dysfunction and demise resembling human glaucoma. I measured structural changes with Optical Coherence Tomography (OCT), and RGC function with Pattern Electroretinogram (PERG). I also developed and refined provocation approaches (IOP elevation with changes in body posture; metabolic load with flickering light) to probe susceptibility of RGC function in D2 mice prone to glaucoma. Finally, I developed a novel system for recording, simultaneously but independently, the PERG from both eyes using asynchronous visual stimuli and deconvolution analysis. Simultaneous PERG recording from each eye was hitherto impossible due to the interocular cross-talk of the PERG signal. Altogether, the combination of these measures (OCT, PERG) and provocative conditions may represent powerful tools for glaucoma research using mouse models.

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Tran, Sung. "Development of a Sensor Readout Integrated Circuit Towards a Contact Lens for Wireless Intraocular Pressure Monitoring." DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1750.

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This design covers the design of an integrated circuit (IC) in support of the active contact lens project at Cal Poly. The project aims to monitor intraocular eye pressure (IOP) to help diagnose and treat glaucoma, which is expected affect 6.3 million Americans by 2050. The IC is designed using IBM’s 130 nm 8RF process, is powered by an on-lens thin film 3.8 V rechargeable battery, and will be fabricated at no cost through MOSIS. The IC features a low-power linear regulator that powers a current-starved voltage-controlled oscillator (CSVCO) used for establishing a backscatter communication link. Additional circuitry is included to regulate power to and from the battery. An undervoltage lockout circuit protects the battery from deep discharge damage. When recharging, a rectifier and a voltage regulator provides overvoltage protection. These circuit blocks are biased primarily using a 696 mV subthreshold voltage reference that consumes 110.5 nA.

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Sawamura, Megumi. "Development of novel treatment against glaucoma; Intraocular pressure-lowering by cytoskeletal drugs and neuroprotection by neurotrophic factors." Kyoto University, 2001. http://hdl.handle.net/2433/150551.

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Je, Shindy. "Changes in spatial summation in response to intraocular pressure-lowering treatment in glaucoma : evidence of neural remodeling?" Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/110760/.

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Kreuz, André Carvalho. "Eletrorretinograma de padrão reverso macular e multifocal e tomografia de coerência óptica em olhos suspeitos de glaucoma e glaucomatosos com perda de hemicampo." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/5/5149/tde-06022017-110458/.

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Objetivos: Avaliar a capacidade do eletrorretinograma de padrão reverso (PERG) macular e multifocal (mf) de diferenciar pacientes com suspeita de glaucoma (SG) e glaucoma com defeito de campo hemianópico (GH) de controles, comparar a capacidade de discriminação do PERG e tomografia de coerência óptica (TCO) fourrier domain, e avaliar a relação entre as medidas do PERG e TCO. Métodos: Medidas do campo visual (CV) computadorizado, respostas do PERG transiente e modo estacionário e PERGmf foram obtidos dos SG (n=14, 24 olhos), GH (n=5, 7 olhos) e controles (n=19, 22 olhos). Os seguintes parâmetros de TCO foram investigados: camada de fibras nervosas da retina peripapilar (CFNRpp), espessura total da mácula e espessuras das camadas segmentadas da mácula. As medidas foram analizadas utilizando-se modelos lineares de efeito misto. Também foi avaliada a relação entre as medidas e a performance diagnóstica de cada tecnologia. Resultados: Comparado aos controles, a média do tempo de pico de P50 da resposta do PERG transiente estava reduzida nos SG e GH, enquanto que a fase, a amplitude do modo estacionário e respostas do PERGmf estavam anormais apenas no GH. A média das medidas da TCO de espessura macular e da CFNRpp nos SG e GH diferiram significativamente dos controles. Uma significativa relação foi observada entre o PERG e a maior parte dos dos parâmetros do CV central e TCO. A análise por regressão e componentes principais revelou que a TCO de nervo óptico e mácula, assim como o PERG transiente e PERGmf tiveram estatisticamente capacidade similar em discriminar os SG dos controles. Conclusões: Os parâmetros do PERG e da TCO podem estar anormais, com significativa relação entre as medidas, em uma porcentagem alta de olhos com SG com CV normal. Nossos achados sugerem que as duas tecnologias podem ser úteis e complementares na detecção precoce de glaucoma
Purpose: To evaluate the ability of macular and multifocal (mf) pattern electroretinogram (PERG) to differentiate glaucoma suspects (GS) and glaucoma with hemifield loss (GHL) from controls, to compare the discrimination ability of PERG and fourier-domain optical coherence tomography (fdOCT), and to assess the relationship between PERG and fdOCT measurements. Methods: Standard automated perimetry (SAP), steady-state and transient PERG responses and mfPERG measurements were obtained from GS (n=14, 24 eyes), GHL (n=5, 7 eyes) and controls (n=19, 22 eyes). The following fdOCT parameters were investigated: circumpapillary retinal nerve fiber layer (cpRNFL), full-thickness macula, and segmented macular layer thicknesses. Measurements were compared using mixed effects linear models. The relationships between measurements and the diagnostic performance of each technology were also assessed. Results: Compared to controls, average P50 peak time transient PERG responses were reduced in GS and GHL, whereas average phase and amplitude steady-state and mfPERG responses were abnormal only in GHL. The average fdOCT-measured cpRNFL and macular thickness measurements in GS and GHL differed significantly from controls. A significant relationship was found between PERG and most fdOCT or central SAP sensitivity parameters. Principal component regression analysis revealed that optic disc and macular OCT parameters, along with mfPERG and transient PERG parameters had statistically similar ability to discriminate GS from controls. Conclusions: PERG and OCT parameters may be abnormal, with significant correlations between measurements, in a high percentage of GS eyes with normal SAP. Our findings suggest that both technologies may be helpful and complementary in early glaucoma detection

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Roubeix, Christophe. "Intérêt des cellules souches mésenchymateuses dans la thérapie du glaucome." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066535/document.

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Le glaucome est une neuropathie optique associée à une augmentation de la pression intraoculaire (PIO). L’élévation de la PIO est due à la dégénérescence progressive du trabéculum. Les traitements antiglaucomateux vise à réduire la PIO, cependant il n’existe aucun traitement ciblant la dégénérescence du trabéculum. Les cellules souches mésenchymateuses (CSMs) sont utilisées comme outils thérapeutiques dans différentes pathologies dégénératives. Elles sécrètent un panel de molécules qui sont décrit comme atténuant les processus dégénératifs. L’objectif de ce travail a été d’évaluer l’intérêt des CSMs dans la prise en charge du glaucome. La caractérisation des CSMs ont été mis au point à partir de culture primaire de moelle osseuse de rat. En parallèle, un modèle expérimental de glaucome par cautérisation des veines épisclérales (EVC) a été réalisé. Nous nous sommes intéressés à l’effet de l’injection intracamérulaire des CSMs dans ce modèle. Les CSMs sont retrouvées incorporées aux tissus autour et dans le trabéculum. Les résultats obtenus in vivo montrent une diminution de la PIO par l’injection des CSMs préservant ainsi les cellules ganglionnaires périphériques de la rétine (CGRs). Par une approche in vitro, nous avons également caractérisé les effets du sécrétome des CSMs sur les cellules impliquées dans la pathologie glaucomateuse: les cellules trabéculaires et les cellules ganglionnaires de la rétine. Ces résultats ont permis de montrer que l’injection intracamérulaire de CSMs permettrait de protéger la fonction de régulation de la PIO et de protéger les CGRs dont la mort est responsable de la diminution de l’acuité visuelle chez le patient glaucomateux
Glaucoma is a sight-threatening retinal neuropathy associated with elevated intraocular pressure (IOP) due to degeneration and fibrosis of the trabecular meshwork (TM). Glaucoma medications aim to reduce IOP without targeting the specific TM pathology, which could explain treatment failure observed in some cases. Bone-marrow mesenchymal stem cells (MSCs) are used today in various clinical studies to treat various degenerative processes. Here, we investigated the potential of MSC therapy in an ocular hypertension model. We demonstrated a rapid and long-lasting in vivo effect of MSC transplantation that significantly reduced IOP in hypertensive eyes induced by episcleral vein cauterization (EVC). MSCs were found located to the ciliary processes and the TM and are able to survive at these places. Enumeration of retinal ganglion cells (RGCs) on whole flat-mounted retina highlighted a protective effect of MSCs on RGC death. In vitro, the effect of MSC-conditioned medium (MSC-CM) on both the primary human trabecular meshwork (hTM) and RGCs showed that MSC-CM promotes: (i) hTM survival by activating the antiapoptotic pathway, Akt, (ii) hTM decontractibility as analyzed by the decrease in myosin phosphorylation and (iii) inhibition of TGF-β2-dependent profibrotic phenotype acquisition in hTM, (iiii) RGC survival and neuritic outgrowth in vitro. Finally, MSCs injection in the ocular anterior chamber in a rat model of ocular hypertension provides a neuroprotective effect in the glaucoma pathophysiology directly on RGC and indirectly via TM protection. These results originally demonstrate that MSCs represent promising tool for treating ocular hypertension and retinal cell degeneration

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Beckman, Rehnman Jeannette. "New methods to evaluate the effect of conventional and modified crosslinking treatment for keratoconus." Doctoral thesis, Umeå universitet, Oftalmiatrik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-110531.

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Background: Today corneal crosslinking with ultraviolet-A photoactivation of riboflavin is an established method to halt the progression of keratoconus. In some cases, when the refractive errors are large and the visual acuity is low, conventional corneal crosslinking may not be sufficient. In these cases it would be desirable with a treatment that both halts the progression and also reduces the refractive errors and improves the quality of vision. Aims: The aims of this thesis were to determine whether mechanical compression of the cornea during corneal crosslinking for keratoconus using a sutured rigid contact lens could improve the optical and visual outcomes of the treatment, and also to find methods to evaluate the effect of different corneal crosslinking treatment regimens. Methods: In a prospective, open, randomized case-control study, 60 eyes of 43 patients with progressive keratoconus, aged 18-28 years, planned for routine corneal crosslinking, and a corresponding age- and sex-matched control group was included. The patients were randomized to conventional corneal crosslinking (CXL; n=30) or corneal crosslinking with mechanical compression of the cornea during the treatment (CRXL; n=30). Biomicroscopy, autorefractometry, best spectacle corrected visual acuity, axial length measurement, Pentacam® HR Scheimpflug photography, pachymetry, intraocular pressure measurements and corneal biomechanical assessments were performed before treatment (baseline) and at 1 month and 6 months after the treatment. One of the articles evaluated and compared the optical and visual outcomes between CXL and CRXL, while the other three articles focused on methods to evaluate treatment effects. In Paper I, the corneal light scattering was manually quantified from Scheimpflug images throughout the corneal thickness at 8 measurements points, 0.0 to 3.0 mm from the corneal centre, in patients treated with CXL. In Paper IV the corneal densitometry (light scattering) was measured with the Pentacam® HR software, in 4 circular zones around the corneal apex and at 3 different depths of the corneal stroma, in both CXL and CRXL treated corneas. Paper III quantified the biomechanical effects of CXL in vivo. Results: Corneal light scattering after CXL showed distinctive spatial and temporal profiles and Applanation Resonance Tonometry (ART) -technology demonstrated an increased corneal hysteresis 1 and 6 months after CXL. When comparing the refractive and structural results after CXL and CRXL, CRXL failed to flatten the cornea, and the treatment did not show any benefits to conventional CXL treatment, some variables even indicated an inferior effect. Accordingly, the increase in corneal densitometry was also less pronounced after CRXL. Conclusions: Analysis of corneal light scattering/densitometry shows tissue changes at the expected treatment location, and may be a relevant variable in evaluating the crosslinking effect. ART -technology is an in vivo method with the potential to assess the increased corneal hysteresis after CXL treatment. By refining the method, ARTmay become a useful tool in the future. Unfortunately, CRXL does not improve the optical and visual outcomes after corneal crosslinking. Possibly, stronger crosslinking would be necessary to stabilize the cornea in a flattened position.

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48

Renzo, Roberta. "Pressão intra-ocular, condições endoteliais e prostaglandina E2 no humor aquoso de cães com catarata senil madura ou hipermatura /." Jaboticabal, 2012. http://hdl.handle.net/11449/88973.

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Orientador: José Luiz Laus
Banca: Adriana Morales
Banca: Alexandre Lima de Andrade
Resumo: Estudaram-se a pressão intraocular, a densidade e a hexagonalidade de células endoteliais, níveis de Prostaglandina E2 e sua correlação com catarata senil madura (n=8) ou hipermatura (n=8). Adicionalmente, foram utilizados valores de Prostaglandina E2 do humor aquoso de cães oftalmologicamente saudáveis (n=7). Para avaliação da pressão intraocular empregou-se tonometria digital de aplanação. A avaliação da densidade e da hexagonalidade das células endoteliais foi realizada por meio de microscopia especular de não contato. Sob anestesia geral, 0,2mL de humor aquoso foram colhidos por meio de paracentese da câmara anterior. As amostras de aquoso foram congeladas e armazenadas à -80 oC para mensuração da concentração de PGE2, por imunoensaio enzimático competitivo. Os valores foram comparados estatisticamente, empregando-se análise de variância de via única, e o teste de múltiplas comparações de Bonferroni. Teste t não pareado foi utilizado para se avaliar os dados obtidos por microscopia especular. Possíveis correlações entre os resultados foram comparadas aplicando-se o teste de Person. Adotou-se nível de significância de p<0,05. Em ambos os grupos observou-se diminuição significativa da pressão intraocular (PIO), entretanto não houve diferença entre eles (p = 0,90). As médias dos valores de densidade celular (CD) e de hexagonalidade (HEX) foram 2253,363 cell/mm² e 59,03% para GSM e 2058,325 cell/mm² e 63,75% para GSH, respectivamente. Entretanto não houve diferença significativa entre ambos, tanto para CD (p=0,201), quanto para HEX (p=0,61). Observou-se incremento nos valores de PGE2 nos grupos com catarata em relação aos cães oftalmologicamente saudáveis (p<0,001), entretanto, não houve diferença significativa entre os grupos com catarata... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Intraocular pressure, endothelial cell density and hexagonality, and aqueous humor prostaglandin E2 (PGE2) were studied and correlated in dogs with mature (n=8) and hypermature (n=8) senil cataratcs. In addition, aqueous humor PGE2 values of ophthalmic healthy dogs (n=7) were used. Non contact specular microscopy was used to evaluate density and hexagonality of endothelial cells. 0.2mL of aqueous humor was collected by means of anterior chamber paracentesis. Aqueous humor samples were frozen at -80 oC and concentration of PGE2 were quantified by means of competitive enzyme immunoassay. PGE2 values were statistically compared with one way analysis of variance and Bonferroni's multi comparison test. Specular microscopy data were assessed by means of unparied T test. Person's test was used in order to assess possible correlations among data. Significance was set at value of P < 0.05. Values of endothelial cell density and hexagonality did not change significantly between groups (P = 0.61). PGE2 values were significantly higher in dogs with cataract, when compared with ophthalmic healthy dogs (P < 0.001), however, this parameter did not change significantly between mature and hypermature groups (P > 0.05). Is it possible tosay that cataract patients in stages of maturity or hipermaturity develop uveitis... (Complete abstract click electronic access below)
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49

Verstappen, Annita A. (Annita Apollonia). "Cellular mechanisms of ocular hypotensive effects of a₂-adrenergic agonists." Thesis, University of North Texas, 1993. https://digital.library.unt.edu/ark:/67531/metadc798263/.

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Th ocular bilateral hypotensive effect after unilateral topical administration of medetomidine and 4 analogs was demonstrated in a dose-response study (0.5%-2%) in NZW rabbits (bilateral IOP-lowering efficacy: medetomidine>detomidine and MPV-1440>MPV-1441 and MPV-305BIII).

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50

Tran, Tung Vu. "Ocular Hypotensive Effect of the α2-Adrenergic Agonist, Lofexidine." Thesis, University of North Texas, 1989. https://digital.library.unt.edu/ark:/67531/metadc501156/.

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A selective a2-adrenergic agonist, lofexidine, significantly reduced intraocular pressure (lOP) in intact ocular normotensive NZW rabbits, producing a differential dose-dependent decrease in IOP in'the ipsilateral and contralateral eye. Contralateral IOP reduction was most observable at low doses. Unilateral superior cervical ganglionectomy and extraocular muscle excision studies were undertaken to elucidate the factors influencing differential IOP reduction by lofexidine. Similar significant contralateral decreases in IOP were noted when the agent was applied to either the intact or operated eye. Biochemical studies demonstrated that lofexidine inhibited isoproterenol-stimulated adenylcyclase in isolated iris-ciliary body preparations. Yohimbine, an α2-adrenergic antagonist, blocked this inhibitory response. Hence, these observations suggested that lofexidine's site of IOP reduction was probably at the cellular level.

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Dissertations / Theses on the topic 'Intraocular pressure'

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