Dissertations / Theses on the topic 'Intraocular pressure – Measurement'
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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.
Full textJóhannesson, 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.
Full textPolyzoev, Vasco. "HAND-HELD TONOMETER FOR TRANSPALPEBRAL INTRAOCULAR PRESSURE MEASUREMENT." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202517.
Full textChiu, 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.
Full textIncludes 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.
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.
Full textIn 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.
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.
Full textHamilton, Kirsten School of Optometry & 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.
Full textLjubimova, 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.
Full textQC 20100729
Ko, Yu-Chieh, and 柯玉潔. "Effects of Corneal Thickness and Curvature on Intraocular Pressure Measurement." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/55931854691351134771.
Full text國立陽明大學
臨床醫學研究所
92
Glaucoma refers a group of diseases with characterized optic neuropathy. They share certain features, including retinal ganglion cell apoptosis, and progressive cupping and atrophy of the optic nerve head, which has attendant visual field loss. Elevated intraocular pressure (IOP) is the most prominent risk factor for glaucoma, and lowering of IOP is the only contemporary ophthalmic intervention that can be reliably effective. Accurate estimation of IOP is important because it is an essential factor in precise patient classification in diagnosis and efficacy assessment of glaucoma treatment. Of all the tonometers being used, Goldmann applanation tonometer (GAT) was considered as the gold standard for IOP measurements for decades. However, studies comparing measurements with manometry and tonometry indicate that measuring central corneal thickness (CCT) is essential to properly interpret the results obtained with GAT. The IOP would be over- or under-estimated in subjects with thick or thin corneas respectively. The realization of a wide range of CCT in normal eyes and the advent of excimer laser refractive surgery prompted ophthalmologists to pay attention to the impact of CCT on IOP measurements. Besides, corneal curvature is also considered as a possible source of error in applanation tonometry. The noncontact tonometer (NCT) is now widely used as a screening tool for glaucoma. However, little is known about the impact of CCT on the NCT measurements. The ocular blood flow tonometer (OBFT) has been introduced as another option to measure IOP and pulsatile ocular blood flow. The manufacturers claim that IOP measurements with the OBFT are not affected by variations in CCT, a statement needs to be verified. In this study, we used three kinds of tonometers (GAT, NCT and OBFT) to measure IOP and performed ultrasound pachometry, and keratometry on glaucoma, ocular hypertension and control subjects. We compared the IOP measurements obtained with the various tonometers and then evaluated the relationship between CCT or corneal curvature and these measurements. After reviewing the literature, we adopted several correction formulae that take CCT and/or corneal curvature into account to estimate the true intraocular hydrostatic pressure from the GAT readings. We quantified the NCT and OBFT measurement errors related to the variation in CCT by using the corrected GAT values as the standard. We found that pressure readings with the GAT, NCT and OBFT were all affected by CCT, with the NCT being the one most affected and the GAT the least. A linear regression model indicated that a 10μm change in CCT could yield a 0.47 – 0.98 mmHg deviation in the NCT measurements and a 0.29 – 0.81 mmHg deviation in the OBFT measurements. For eyes with keratometric astigmatism less than 2 diopters, corneal curvature had no significant correlation with the IOP measurements.
Kuei, Cheng-Kai, and 桂承楷. "Design, Fabrication and Measurement of RFID Tag for Intraocular Pressure Monitoring." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/vyrr2c.
Full text國立交通大學
電控工程研究所
103
In order to achieve long-term intraocular pressure (IOP) monitoring, this thesis presents a wireless readout system based on radio frequency identification (RFID) technology used to readout contact lens IOP sensor device. A digital baseband circuit, receive antenna and transmit antenna has been designed and fabricated to implement a pre-testing wireless IOP sensing tag. Considering the restriction on antenna size which is limited by contact lens, this thesis used 860 ~ 960 MHz as communication frequency band, designed a single-loop like antenna using inductive coupling to obtain higher energy transmission efficiency in near field under the conditions that the size of antenna is much smaller than the wavelength. The proposed sensing tag can perform 2 cm wireless sensing with 12.6 dBm RF power, and reached the maximum sensing distance of 7 cm under 30 dBm, which has met the requirement of our application. Furthermore, a next generation receive antenna has been designed and simulated, according to the pre-testing result, a 18.2 dBm RF power is needed to accomplish wireless sensing at distance of 2 cm.
Anigulu, Mohan Deepak Kumar. "Design of fully integrated wireless CMOS MEMS device for intraocular pressure measurement." 2006. http://www.lib.ncsu.edu/theses/available/etd-04282006-012435/unrestricted/etd.pdf.
Full textKwon, Tae-Hyun. "Minimally invasive characterization and intraocular pressure measurement via numerical simulation of human cornea /." 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3250274.
Full textSource: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 1116. Advisers: Jamshid Ghaboussi; David Pecknold. Includes bibliographical references (leaves 120-126) Available on microfilm from Pro Quest Information and Learning.
Yao, Po-Hsi, and 姚博熙. "The Modeling and Biomechanical Analysis of Human Cornea for Non-contact Intraocular Pressure Measurement." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/56207346517294226567.
Full text國立交通大學
電機與控制工程系所
97
The purpose of this thesis is to provide a Non-contact intraocular pressure measurement. The intraocular pressure variation will cause cornea deformation. That can be used to calculate intraocular pressure by optical measure, and to give up the measurement that used contact cornea to cause specific deformation. It will achieve the goal that used non-contact intraocular pressure measurement and provide a more comfortable measurement. On the side, we build up the finite element model for cornea. It can be used to simulate intraocular pressure variation about deformation, and discuss about corneal thickness and Young’s modulus. We also try to find out the relationship from intraocular pressure variation and deformation. That will be used to calculate the intraocular pressure and demonstrate feasibility for the non-contact intraocular pressure measurement.
Yeh, Guan-Ting, and 葉冠廷. "Design, Fabrication and Measurement of Contact Lenses with Capacitor Sensor for Intraocular Pressure Monitoring." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/bmfx67.
Full text國立交通大學
電控工程研究所
102
The main sensing principle based on intraocular pressure(IOP) caused by natural variations in corneal deformation, using capacitive IOP contact lenses sensor paste clothes in cornea and sensing changes in the manner in which the corneal contour changes in intraocular pressure indirectly. This paper reports a study of the use of MEMS manufacturing technology to fabricate a flexible IOP sensor that can be embedded in a contact lens, using a transparent parylene C as a substrate and an insulating layer, gold as the upper and lower electrode of the capacitor electrode. It is a cyclic structure consists of two structural sandwich plates which is filled by HEMA and between top plate and bottom plate. Then the sensor will combined with contact lens molds. After combining contact lens surface smooth and no wrinkles. Biocompatible materials had been used. This sensor shows a high sensitivity, fast dynamic response, and less susceptible to environmental effects. Also it won’t be affected by high frequency signal, and can reduce the difficulty of the design of circuit. In the dynamic measurement section, the sensor is placed on self-designed and size similar bionic eye for sensor dynamic testing. Results show that when the bionic eye cavity was poured into 50 uL of water, bionic eye curvature produce very small changes, the sensor can correctly detect and have a fairly good reproducibility and response speed. Sensor sensitivity is about 0.5 pF / mmHg.
Wu, Tsung-Wei, and 吳宗瑋. "The Study of Fabrication Feasibility, Packaging and Measurement of Contact Lenses with Capacitor Sensor for Intraocular Pressure Monitoring." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/cvt45a.
Full text國立交通大學
電控工程研究所
103
The main sensing principle is detecting the corneal deformation caused by the variations of intraocular pressure(IOP), using capacitive IOP contact lenses sensor wear on corneal. The variations of intraocular pressure will be transformed into the change of capacitance values and the values will be exported by RFID system. Reach the goals of long time, comfort, and wireless measurement. This paper reports a study of using MEMS manufacturing technology to fabricate a flexible IOP sensor that can be embedded in a contact lens with the feasibility fabrication. The first part is the fabrication of sensing unit which is a sandwich structure which is filled by HEMA between top plate and bottom plate, using a transparent parylene C as the substrate and the insulating layer, gold as the top and bottom electrode of the capacitor electrode. The second part is the fabrication of sensor, it will be integrated by using the Flip-Chip technology to combine the sensing unit and the chip with read-out circuit, molding into contact lenses with PDMS, and curing with oven. Last, the experiment of the qualitative and quantitative of the sensor will be implemented by using isolated pig eyes and living rabbit eyes.
(6615704), Rachael Swenson. "Design of a Closed Loop System for Glaucoma Treatment including Measurement of Intraocular Pressure and Therapeutic Stimulation of the Eye." Thesis, 2019.
Find full textGlaucoma is the leading cause of irreversible blindness worldwide effecting more than 2.7 million people in the U.S alone. Treatments exist in the form of both pharmaceutical and surgical options, but often do not provide the desired efficacy. For example, the failure rate of a trabeculectomy procedure is 39% within 5 years. Additionally, none of the current glaucoma treatments allow for closed loop monitoring of pressure, therefore requiring more frequent doctor visits. Glaucoma management can be improved through the use of a closed loop application of electroceutical treatment. The goal is to develop an implantable device that will be inserted into the eye to monitor intraocular pressure (IOP) and provide responsive therapeutic stimulation to the eye. I designed a discrete pressure monitoring system that interacts with a bare die piezoresistive pressure sensor. The system is based on a Wheatstone bridge design which translates the input resistances of the pressure sensor into a voltage output. This system has an average accuracy of 0.53 mmHg and draws 295 µW of power. I then combined this pressure system with data processing code and Howland current pump stimulation circuitry. This simulation system can output up to 1.05 mA of current for electroceutical intraocular stimulation to lower IOP. Future work will involve miniaturizing the circuitries in the form of an ASIC and packaging the entire system into an ocular implant. This implant can wirelessly monitor IOP and provide therapeutic stimulation to lower IOP. A reliable, closed loop method of lowering IOP would greatly benefit the ever-growing population affected by glaucoma.
Sayah, Diane Noël. "Ocular rigidity : a previously unexplored risk factor in the pathophysiology of open-angle glaucoma : assessment using a novel OCT-based measurement method." Thesis, 2020. http://hdl.handle.net/1866/24253.
Full textGlaucoma is the leading cause of irreversible blindness worldwide. While its pathogenesis is yet to be fully understood, the biomechanical properties of the eye are thought to be involved in the development and progression of this disease. Ocular rigidity (OR) is thought to be altered through disease processes and has been suggested to be the most influential factor on the optic nerve head’s response to variations in intraocular pressure (IOP) in glaucoma. To further investigate the role of OR in open-angle glaucoma (OAG) and other ocular diseases such as myopia, the ability to quantify OR in living human eyes using a reliable and non-invasive method is essential. Such a method has only become available in 2015. Based on the Friedenwald equation, the method uses time-lapse optical coherence tomography (OCT) imaging and automated choroidal segmentation to measure the pulsatile choroidal volume change (ΔV), and Pascal dynamic contour tonometry to measure the corresponding pulsatile pressure change. The purpose of this thesis work was to assess the validity of the methodology, then use it to investigate the role of OR in ocular diseases, particularly in OAG. More specifically, the objectives were: 1) To improve the extrapolation of ΔV and evaluate the method’s validity and repeatability, 2) To investigate the association between OR and neuro-retinal damage in glaucomatous patients, as well as those with concomitant vasospasticity, 3) To evaluate the association between OR and corneal biomechanical parameters, 4) To assess the association between OR and IOP spikes following therapeutic intravitreal injections (IVIs), to predict and prevent them in high-risk patients, and 5) To confirm that OR is lower in myopia. First, we improved the mathematical model of the eye used to derive ΔV by rendering it more anatomically accurate and accounting for the peripheral choroid. We also confirmed the validity and good repeatability of the method. We carried out the measurement of OR coefficients on a wide range of healthy and glaucomatous subjects using this non-invasive method, and were able to show, for the first time, that lower OR is correlated with more glaucomatous damage. The correlations observed were comparable to those obtained with recognized risk factors such as maximum IOP. A strong correlation between OR and neuro-retinal damage was found in patients with concurrent vasospastic syndrome, but not in those with ischemic vascular disease. This could perhaps indicate a greater susceptibility to glaucoma due to ocular biomechanics in vasospastic patients. While corneal biomechanical parameters have been widely adopted in clinical practice as surrogate measurements for the eye’s overall biomechanical properties represented by OR, we have shown a limited association between these parameters, bringing new insight unto the relationship between corneal and global biomechanical properties. Only a weak correlation between the corneal resistance factor and OR remained in glaucomatous eyes after adjusting for confounding factors. In addition, we presented a model to predict the magnitude of IOP spikes following IVIs from the non-invasive measurement of OR. This is particularly useful for high-risk patients with exudative retinal diseases and glaucoma that require therapeutic IVIs, and could provide the clinician an opportunity to adjust or customize treatment to prevent further vision loss. Finally, we investigated OR differences between non-myopic and myopic eyes using this technique, and demonstrated lower OR in axial myopia, a risk factor for OAG. Overall, these findings provide new insights unto the pathophysiology of glaucomatous optic neuropathy. The development of our method will permit further investigation of the role of OR in ocular diseases, contributing to elucidate mechanisms and provide novel management options to counter vision impairment caused by these diseases.
"A comparison of intraocular pressure measurements using rebound tonometry (iCare® tonometer) and applanation tonometry (Goldmann tonometer) in a South African clinical setting." Thesis, 2015. http://hdl.handle.net/10210/14040.
Full textThe primary aim of this research was to investigate whether the Icare® rebound tonometer may be used in place of the Goldmann tonometer to obtain accurate and reliable intraocular pressure measurements on a sample of the general population seeking eye care, in a South African context. Due to the portability of the Icare®, lack of dependency on other instrumentation and power source, together with the ease of use with minimal training, and without the use of topical anaesthetic favourable results of the instrument may lead to its widespread use. This could aid in earlier diagnosis of glaucoma where intraocular pressure remains the only modifiable risk factor. In the South African context, where a high prevalence of undiagnosed primary open angle glaucoma has been found, access and accuracy of intraocular pressure measurement could save and extend functional vision in this country. Patients presenting at the Department of Optometry for routine eye examinations were selected utilizing convenience sampling. The right and left eyes of 113 patients were assessed using both the Icare® TA01i and the Goldman applanation tonometer by independent examiners for each method, all readings of intraocular pressure with the Goldman being taken by the same experienced examiner. The age of the patients ranged from 20 to 89 years with a mean age 50.29 ±20.97 years. Using the Oculus Pachycam® when it became available, central corneal thickness was obtained on 71 patients (142 eyes). Analysis of data using descriptive statistics from SPSS (Statistical Programs for the Social Sciences) was performed in addition to the Bland-Altman method of comparative analysis for sets of data of corrected and uncorrected measurements between the instruments...