Relevant bibliographies by topics / Corneal lens

Academic literature on the topic 'Corneal lens'

Author: Grafiati
Published: 6 September 2023

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Journal articles on the topic "Corneal lens"

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Mishra, S. K., G. S. Shrestha, P. Dhungel, and B. Aryal. "Visual outcome on Fitting Rose-K2 XL lens in a case with Terrien’s marginal degeneration." Journal of Chitwan Medical College 4, no. 4 (January 28, 2015): 49–51. http://dx.doi.org/10.3126/jcmc.v4i4.11974.

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Terrien’s marginal degeneration is an uncommon disease of the peripheral cornea occurring at any age that results in corneal thinning causing corneal irregular astigmatism. RoseK2 XL lens has an aspheric optical zone and employed in the fitting of irregular corneas for vision and comfort while maintaining corneal health. Rose K2 XL lens was fitted in a 17 year female presented to Contact lens clinic of B.P. Koirala Lions Center for Ophthalmic Studies, Kathmandu having RE Terrien’s marginal degeneration. Her presenting visual acuity was 6/60 in right eye and 6/6 in left eye with best subjective refraction OD: +2.00/-3.00X150 and OS: Plano. Her corneal topography revealed irregular corneal astigmatism as indicated by SimK49.85/41.63@137. RoseK2 XL which is a mini-scleral lens, showed an excellent fitting attaining visual acuity 6/6. RoseK2 XL lens provides not only good visual acuity also confirms comfort in patients with corneal marginal degeneration.DOI: http://dx.doi.org/10.3126/jcmc.v4i4.11974
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Shi, Rong, Weize Wang, Yu Che, Shaorong Linghu, and Taixiang Liu. "Effects of Corneal Stromal Lens Collagen Cross-Linking Regraft on Corneal Biomechanics." Journal of Ophthalmology 2022 (June 8, 2022): 1–7. http://dx.doi.org/10.1155/2022/8372156.

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Background. Corneal collagen cross-linking (CXL) therapy, a method that uses a combination of riboflavin and ultraviolet-A light (UVA), can promote the formation of covalent cross-linking of amino acid residues of corneal collagen and enhance the hardness of the cornea. In this study, we explored the effects of corneal stromal lens collagen cross-linking regraft on corneal biomechanics. Methods. A total of 15 New Zealand white rabbits were divided into 3 groups: normal control group (group A), SMILE + uncross-linked lens implantation group (Group B), and SMILE + cross-linking lens implantation group (group C). The design parameters of SMILE surgery were as follows: the corneal cap was 120 um thick, the lens diameter was 6.5 mm, and the diopter was -6.0D. Riboflavin and ultraviolet-A (UVA) were used as corneal stromal lens CXL, which was implanted into the allogeneic rabbit corneal stromal bag 24 hours after the operation. Postoperative corneal thickness (CCT), refraction, AS-OCT, and corneal biomechanics were performed before and then at 1 and 3 months after the operation. Results. All corneas appeared transparent and smooth 3 months after surgery. The corneal thicknesses of both group B and group C were lower than those before the operation. The corrected refraction of group B and group C after lens implantation was also lower than the expected corrected power; there was no significant difference between the two groups ( P > 0.05 ). AS-OCT results showed an uneven surface and thickness of the corneal stromal lens in two eyes of group B. Moreover, corneal elastic deformation increased with intraocular pressure in each group; displacement from large to small was group B > group C and > group A. The creep from large to small was group B > group C > group A. The fiberboard layers of groups B and C were disordered, and there were a few autophagosomes in the fibroblasts of group B by transmission electron microscopy (TEM). Conclusions. Allograft graft of corneal stromal lens collagen cross-linked can significantly increase the biomechanical properties of the cornea.
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Jester, J. V., T. Moller-Pedersen, J. Huang, C. M. Sax, W. T. Kays, H. D. Cavangh, W. M. Petroll, and J. Piatigorsky. "The cellular basis of corneal transparency: evidence for ‘corneal crystallins’." Journal of Cell Science 112, no. 5 (March 1, 1999): 613–22. http://dx.doi.org/10.1242/jcs.112.5.613.

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In vivo corneal light scattering measurements using a novel confocal microscope demonstrated greatly increased backscatter from corneal stromal fibrocytes (keratocytes) in opaque compared to transparent corneal tissue in both humans and rabbits. Additionally, two water-soluble proteins, transketolase (TKT) and aldehyde dehydrogenase class 1 (ALDH1), isolated from rabbit keratocytes showed unexpectedly abundant expression (approximately 30% of the soluble protein) in transparent corneas and markedly reduced levels in opaque scleral fibroblasts or keratocytes from hazy, freeze injured regions of the cornea. Together these data suggest that the relatively high expressions of TKT and ALDH1 contribute to corneal transparency in the rabbit at the cellular level, reminiscent of enzyme-crystallins in the lens. We also note that ALDH1 accumulates in the rabbit corneal epithelial cells, rather than ALDH3 as seen in other mammals, consistent with the taxon-specificity observed among lens enzyme-crystallins. Our results suggest that corneal cells, like lens cells, may preferentially express water-soluble proteins, often enzymes, for controlling their optical properties.
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Severinsky, Boris. "Silicone Hydrogel Miniscleral Contact Lenses after Corneal Collagen Crosslinking for Post-LASIK Keratoectasia." International Journal of Keratoconus and Ectatic Corneal Diseases 3, no. 3 (2014): 127–29. http://dx.doi.org/10.5005/jp-journals-10025-1092.

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ABSTRACT Purpose To report successful visual rehabilitation of post refractive surgery keratoectasia shortly after corneal collage crosslinking (CXL) procedure achieved with silicone hydrogel mini-scleral (SHmS) contact lens. Materials and methods A 29-year-old woman attended to our clinic with complaints on decreased vision in her left eye. Twelve years earlier she underwent bilateral laser-assisted in situ keratomileusis (LASIK) procedure for myopia correction. Corneal topography revealed bilateral central keratoectasia with maximal keratometry values of 55.4 Diopter (D) for her right eye and 59.7 D for the left, corneal thicknesses were 422 and 443 respectively. The patient underwent an uneventful CXL procedure in her left eye and was fitted with SHmS lens 5 weeks later. The lens was designed to rest over the patients’ sclera and perilimbal cornea and vault the central cornea with minimal support over it. Results SHmS lens fitting resulted in significant subjective improvement in visual acuity (from 20/200, unaided to 20/25, contact lens corrected). The patient was able to wear the lens upto 10 hours a day with stable contact lens corrected vision. No contact lens related complications, such as edema or neovascularization were observed during 3 months follow-up period. As a result of successful restoration of vision in the CXL-treated eye, the patient was scheduled for the procedure in her other eye. Conclusion SHmS contact lens should be considered as an option for the visual rehabilitation of corneas shortly after collagen corneal crosslinking procedure. This novel contact lens modality made from flexible and highly gas permeable material minimizes contact lens influence on corneal recovery after CXL and provides an excellent visual outcome. How to cite this article Severinsky B. Silicone Hydrogel Mini-scleral Contact Lenses after Corneal Collagen Crosslinking for Post-LASIK Keratoectasia. Int J Kerat Ect Cor Dis 2014;3(3):127-129.
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Rathor, Jogendra Kumar, Usman Memon, and Jignesh Jethva. "Effect of spherical rigid gas permeable lens on correction of corneal astigmatism." International Journal Of Community Medicine And Public Health 7, no. 12 (November 25, 2020): 4958. http://dx.doi.org/10.18203/2394-6040.ijcmph20205169.

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Background: Objectives were to study an effect of spherical RGP (rigid gas permeable) contact lens in correcting high corneal astigmatism more than 3 diopter.Methods: Total 48 eyes with corneal astigmatism greater than 3.00 diopter were included in study. At the first visit, routine preliminary examination, parameter assessment and subjective refraction has been carried out followed by patient counselling for RGP lens wear. Based on the corneal parameters considering keratometry as well as corneal topography, RGP lens trial was done. Post adaptation period, lens fitting analysis was done by understanding Fluorescein pattern with slit lamp and over refraction was done. Final lens has been ordered on this basis with understanding of tear lens formed, lens performance on cornea and edge width minimal of 0.80 mm to 1.00 mm. Patients were assessed at an interval of every two months from a date of lens dispensing.Results: The spherical RGP lens did correct the corneal astigmatism of more than 3D by formation of tear lens between cornea and lens. Vision improved by 2 to 3 lines compared to the spectacle correction without compromising corneal integrity at the central or peripheral cornea. Keratoconic eye showed significant vision improvement without the use of toric lens.Conclusions: Astigmatic eyes showed significant improvement in acuity with spherical RGP lens without compromising corneal integrity.
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Yang, Seung Ahn, Su Hwan Park, and Ji Eun Lee. "Clinical Use of Mini-Scleral Contact Lens in Ocular Surface Diseases." Annals of Optometry and Contact Lens 21, no. 3 (September 30, 2022): 99–103. http://dx.doi.org/10.52725/aocl.2022.21.3.99.

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A scleral contact lens lies on the sclera, not the cornea, which differs from a rigid gas permeable (RGP) contact lens, and has shown successful clinical outcomes in patients unable to tolerate glasses or RGP contact lenses because of a severely deformed cornea. In addition, a scleral lens forms a tear film between the cornea and contact lens that stabilizes the ocular surface and could be a useful therapeutic option. The mini-scleral contact lens is a useful therapeutic option for visual improvement and symptom control in patients with corneal abnormalities such as keratoconus, corneal opacity, ocular surface disease, and irregular corneal astigmatism.
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Spiteri, Natasha, Anshoo Choudhary, and Stephen Kaye. "Pigmentation of the Cornea Secondary to Tinted Soft Contact Lens Wear." Case Reports in Ophthalmological Medicine 2012 (2012): 1–2. http://dx.doi.org/10.1155/2012/852304.

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Purpose. To report a case of pigmented corneal iron lines following use of tinted soft contact lenses (CL).Methods. A retrospective case report.Results. A 16-year-old girl was referred with suspected CL-related keratopathy OU, having recently switched to tinted soft monthly disposable CLs (8.4/14.0 −3.00 OD, −3.25 OS Aquamarine SofLens Natural Colours, Bausch and Lomb, New York, USA). Both corneas exhibited symmetric superficial corneal pigmented iron lines, which gradually disappeared following discontinuation of CL wear.Conclusions. Pigmented corneal rings have been reported in normal ageing corneas, in certain pathological conditions, and in association with altered corneal topography following LASIK and orthokeratology. We suspect a poorly fitting CL resulted in localised tear pooling between the CL and cornea, and subsequent iron pigment deposition, similar to that seen with orthokeratology. Cosmetic CLs bought via the Internet can be used in an unsupervised manner, with possible impacts on visual function and potential complications.
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Willcox, M. D. P., and B. A. Holden. "Contact Lens Related Corneal Infections." Bioscience Reports 21, no. 4 (August 1, 2001): 445–61. http://dx.doi.org/10.1023/a:1017991709846.

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This article describes microbial keratitis, infection of the cornea by micro-organisms. Contact lens wear is a predisposing factor for the development of microbial keratitis. Micro-organisms probably adhere to the contact lens, transfer from the contact lens to a damaged or compromised corneal epithelial surface, penetrate into the deeper layers of the cornea and produce corneal damage. Host responses to the invading micro-organisms, while designed to protect the eye, can often exacerbate the situation and the resulting microbial keratitis can lead to permanent blindness. The microbial, biochemical and immunological aspects of MK will be described in detail.
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Grzybowski, Andrzej, and Piotr Kanclerz. "Tadeusz Krwawicz, MD: The inventor of cryosurgery in ophthalmology." European Journal of Ophthalmology 29, no. 3 (January 14, 2019): 348–56. http://dx.doi.org/10.1177/1120672118823125.

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Tadeusz Krwawicz (1910–1988) pioneered the use of cryosurgery in, as ophthalmology. The idea arose in 1959 while experimenting because on lyophilization to store corneas and lenses for transplantation it was difficult to remove the lens without damage the capsule was usually torn. Subsequent experiments on rabbits revealed that touching the lens with a wire cooled to 203°K (–70°C) resulted in firm attachment of the lens capsule and subcapsular masses. A cryoextractor was developed and employed for clinical use in cataract extraction, likewise in intumescent cataracts and lens subluxation. Cataract surgery utilizing cryoextraction led to substantial progress to ophthalmology by reducing the number of complications, particularly capsule rupture, and resulted in achieving better outcome compared to other methods. This surgery soon and for almost 20 years became a routine method used all around the world in cataract removal. Simultaneously, Krwawicz developed techniques for corneal refractive surgery—partial lamellar removal of the corneal stroma and temporary interlaminar introduction of a plastic disk in order to change the corneal curvature. Krwawicz presented other ophthalmic interests—his research concerned immunology, histology, histochemistry, biochemistry of ocular tissue, and mainly corneal and experimental surgery with a particular focus on the pathology of the cornea.
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Chukwuemeka, Obinwanne Junior, Damian C. Echendu, Isaura Ilorena D'Alva Brito dos Santos, Sharon Onwuka, and Osazee Agbonlahor. "REGIONAL VARIATION IN FLUID RESERVOIR THICKNESS, OXYGEN TRANSMISSIBILITY AND CORNEAL OEDEMA DURING SCLERAL LENS WEAR." Journal of Contact lens Research and Science 5, no. 1 (December 17, 2021): e32-e43. http://dx.doi.org/10.22374/jclrs.v5i1.48.

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Purpose: To determine if regional variation in post lens fluid reservoir thickness (PLFT) during scleral lens wear leads to regional variation in oxygen transmissibility and corneal edema during 4 hours of non-fenestrated scleral lens wear.Methods: About 20 healthy subjects (mean age, 28.8 ± 4.2 years) were fitted with nonfenestrated rotationally symmetric scleral lenses. Anterior segment optical coherence tomography was used to measure cornea thickness before and after lens wear, PLFT 10 minutes and 4 hours after lens application, and scleral lens thickness (with the scleral lens in situ) 4 hours after scleral lens application. These measurements were limited to the central 6 mm and divided into three zones (central, mid-peripheral, and peripheral zones). In the mid-peripheral and peripheral zones, eight principal meridians were measured, generating 17 measurement points in total. Scleral lens thickness and PLFT measurements were corrected for optical distortions by a series of equations. Oxygen transmissibility was calculated by dividing the scleral lens oxygen permeability by the optically-corrected scleral lens thickness, taking into account the oxygen permeability of saline and fluid reservoir thickness.Results: A significant regional variation in PLFT (F = 12.860, P = 0. 012) was observed after 10 minutes of the lens application, PLFT was thickest and thinnest in the inferotemporal and the superonasal region of the peripheral zones( 322.6 ± 161.8 µm and 153.8 ± 96.4 µm, respectively); however, this variation was not statistically significant at 4 hours of scleral lens wear (F = 4.692; P = 0.073). Despite significant regional variation in oxygen transmissibility (F = 48.472; P = 0.001) and relatively low oxygen transmissibility through the scleral lens, induced corneal edema did not vary significantly in different regions (F = 3.346; P = 0.126). In the central corneal region, the induced corneal edema correlated moderately with PLFT (r = 0.468; P = 0.037) and oxygen transmissibility (r = -0.528; P = 0.017). This relationship was insignificant in the peripheral cornea.Conclusion: The inferotemporal peripheral region had the thickest PLFT and least oxygen transmissibility, and the superonasal region had the vice versa. Despite significant variation in PLFT and oxygen transmissibility initially, in healthy corneas, this variation does not seem to induce statistically significant regional variation in corneal edema. Increased central PLFT and decreased oxygen transmissibility moderately correlate with central corneal edema.
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Dissertations / Theses on the topic "Corneal lens"

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Eom, Youngsub, Dongok Ryu, Dae Wook Kim, Seul Ki Yang, Jong Suk Song, Sug-Whan Kim, and Hyo Myung Kim. "Development of a program for toric intraocular lens calculation considering posterior corneal astigmatism, incision-induced posterior corneal astigmatism, and effective lens position." Springer, 2016. http://hdl.handle.net/10150/621786.

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Background: To evaluate the toric intraocular lens (IOL) calculation considering posterior corneal astigmatism, incision-induced posterior corneal astigmatism, and effective lens position (ELP). Methods Two thousand samples of corneal parameters with keratometric astigmatism >= 1.0 D were obtained using boot-strap methods. The probability distributions for incision-induced keratometric and posterior corneal astigmatisms, as well as ELP were estimated from the literature review. The predicted residual astigmatism error using method D with an IOL add power calculator (IAPC) was compared with those derived using methods A, B, and C through Monte-Carlo simulation. Method A considered the keratometric astigmatism and incision-induced keratometric astigmatism, method B considered posterior corneal astigmatism in addition to the A method, method C considered incision-induced posterior corneal astigmatism in addition to the B method, and method D considered ELP in addition to the C method. To verify the IAPC used in this study, the predicted toric IOL cylinder power and its axis using the IAPC were compared with ray-tracing simulation results. Results The median magnitude of the predicted residual astigmatism error using method D (0.25 diopters [D]) was smaller than that derived using methods A (0.42 D), B (0.38 D), and C (0.28 D) respectively. Linear regression analysis indicated that the predicted toric IOL cylinder power and its axis had excellent goodness-of-fit between the IAPC and ray-tracing simulation. Conclusions The IAPC is a simple but accurate method for predicting the toric IOL cylinder power and its axis considering posterior corneal astigmatism, incision-induced posterior corneal astigmatism, and ELP.
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Tyagi, Garima. "Ocular surface changes with short-term contact lens wear." Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/49758/1/Garima_Tyagi_Thesis.pdf.

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Contact lenses are a common method for the correction of refractive errors of the eye. While there have been significant advancements in contact lens designs and materials over the past few decades, the lenses still represent a foreign object in the ocular environment and may lead to physiological as well as mechanical effects on the eye. When contact lenses are placed in the eye, the ocular anatomical structures behind and in front of the lenses are directly affected. This thesis presents a series of experiments that investigate the mechanical and physiological effects of the short-term use of contact lenses on anterior and posterior corneal topography, corneal thickness, the eyelids, tarsal conjunctiva and tear film surface quality. The experimental paradigm used in these studies was a repeated measures, cross-over study design where subjects wore various types of contact lenses on different days and the lenses were varied in one or more key parameters (e.g. material or design). Both, old and newer lens materials were investigated, soft and rigid lenses were used, high and low oxygen permeability materials were tested, toric and spherical lens designs were examined, high and low powers and small and large diameter lenses were used in the studies. To establish the natural variability in the ocular measurements used in the studies, each experiment also contained at least one “baseline” day where an identical measurement protocol was followed, with no contact lenses worn. In this way, changes associated with contact lens wear were considered in relation to those changes that occurred naturally during the 8 hour period of the experiment. In the first study, the regional distribution and magnitude of change in corneal thickness and topography was investigated in the anterior and posterior cornea after short-term use of soft contact lenses in 12 young adults using the Pentacam. Four different types of contact lenses (Silicone hydrogel/ Spherical/–3D, Silicone Hydrogel/Spherical/–7D, Silicone Hydrogel/Toric/–3D and HEMA/Toric/–3D) of different materials, designs and powers were worn for 8 hours each, on 4 different days. The natural diurnal changes in corneal thickness and curvature were measured on two separate days before any contact lens wear. Significant diurnal changes in corneal thickness and curvature within the duration of the study were observed and these were taken into consideration for calculating the contact lens induced corneal changes. Corneal thickness changed significantly with lens wear and the greatest corneal swelling was seen with the hydrogel (HEMA) toric lens with a noticeable regional swelling of the cornea beneath the stabilization zones, the thickest regions of the lenses. The anterior corneal surface generally showed a slight flattening with lens wear. All contact lenses resulted in central posterior corneal steepening, which correlated with the relative degree of corneal swelling. The corneal swelling induced by the silicone hydrogel contact lenses was typically less than the natural diurnal thinning of the cornea over this same period (i.e. net thinning). This highlights why it is important to consider the natural diurnal variations in corneal thickness observed from morning to afternoon to accurately interpret contact lens induced corneal swelling. In the second experiment, the relative influence of lenses of different rigidity (polymethyl methacrylate – PMMA, rigid gas permeable – RGP and silicone hydrogel – SiHy) and diameters (9.5, 10.5 and 14.0) on corneal thickness, topography, refractive power and wavefront error were investigated. Four different types of contact lenses (PMMA/9.5, RGP/9.5, RGP/10.5, SiHy/14.0), were worn by 14 young healthy adults for a period of 8 hours on 4 different days. There was a clear association between fluorescein fitting pattern characteristics (i.e. regions of minimum clearance in the fluorescein pattern) and the resulting corneal shape changes. PMMA lenses resulted in significant corneal swelling (more in the centre than periphery) along with anterior corneal steepening and posterior flattening. RGP lenses, on the other hand, caused less corneal swelling (more in the periphery than centre) along with opposite effects on corneal curvature, anterior corneal flattening and posterior steepening. RGP lenses also resulted in a clinically and statistically significant decrease in corneal refractive power (ranging from 0.99 to 0.01 D), large enough to affect vision and require adjustment in the lens power. Wavefront analysis also showed a significant increase in higher order aberrations after PMMA lens wear, which may partly explain previous reports of "spectacle blur" following PMMA lens wear. We further explored corneal curvature, thickness and refractive changes with back surface toric and spherical RGP lenses in a group of 6 subjects with toric corneas. The lenses were worn for 8 hours and measurements were taken before and after lens wear, as in previous experiments. Both lens types caused anterior corneal flattening and a decrease in corneal refractive power but the changes were greater with the spherical lens. The spherical lens also caused a significant decrease in WTR astigmatism (WRT astigmatism defined as major axis within 30 degrees of horizontal). Both the lenses caused slight posterior corneal steepening and corneal swelling, with a greater effect in the periphery compared to the central cornea. Eyelid position, lid-wiper and tarsal conjunctival staining were also measured in Experiment 2 after short-term use of the rigid and SiHy contact lenses. Digital photos of the external eyes were captured for lid position analysis. The lid-wiper region of the marginal conjunctiva was stained using fluorescein and lissamine green dyes and digital photos were graded by an independent masked observer. A grading scale was developed in order to describe the tarsal conjunctival staining. A significant decrease in the palpebral aperture height (blepharoptosis) was found after wearing of PMMA/9.5 and RGP/10.5 lenses. All three rigid contact lenses caused a significant increase in lid-wiper and tarsal staining after 8 hours of lens wear. There was also a significant diurnal increase in tarsal staining, even without contact lens wear. These findings highlight the need for better contact lens edge design to minimise the interactions between the lid and contact lens edge during blinking and more lubricious contact lens surfaces to reduce ocular surface micro-trauma due to friction and for. Tear film surface quality (TFSQ) was measured using a high-speed videokeratoscopy technique in Experiment 2. TFSQ was worse with all the lenses compared to baseline (PMMA/9.5, RGP/9.5, RGP/10.5, and SiHy/14) in the afternoon (after 8 hours) during normal and suppressed blinking conditions. The reduction in TFSQ was similar with all the contact lenses used, irrespective of their material and diameter. An unusual pattern of change in TFSQ in suppressed blinking conditions was also found. The TFSQ with contact lens was found to decrease until a certain time after which it improved to a value even better than the bare eye. This is likely to be due to the tear film drying completely over the surface of the contact lenses. The findings of this study also show that there is still a scope for improvement in contact lens materials in terms of better wettability and hydrophilicity in order to improve TFSQ and patient comfort. These experiments showed that a variety of changes can occur in the anterior eye as a result of the short-term use of a range of commonly used contact lens types. The greatest corneal changes occurred with lenses manufactured from older HEMA and PMMA lens materials, whereas modern SiHy and rigid gas permeable materials caused more subtle changes in corneal shape and thickness. All lenses caused signs of micro-trauma to the eyelid wiper and palpebral conjunctiva, although rigid lenses appeared to cause more significant changes. Tear film surface quality was also significantly reduced with all types of contact lenses. These short-term changes in the anterior eye are potential markers for further long term changes and the relative differences between lens types that we have identified provide an indication of areas of contact lens design and manufacture that warrant further development.
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Murphy, Paul J. "An examination of human corneal sensitivity by non-invasive methods." Thesis, Glasgow Caledonian University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336652.

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The aim of this thesis was to design, develop and evaluate a Non-Contact Corneal Aesthesiometer (NCCA), using a controlled pulse of air, of a pre-determined pressure. First, the system design and alterations are described, then in a series of model experiments, the standardisation and characteristics of the air-pulse were examined. These studies revealed that the NCCA could produce a repeatable stimulus of known volume and rate of air-flow. Furthermore, the air-flow exiting the stimulus air jet was of a laminar shape, with minimal dispersion. The control of the air-flow dispersion was further enhanced by using a 0.5mm diameter air jet and a working distance of lcm. Varying the stimulus duration was not found to influence these qualities of the air-pulse. The air-pulse stimulus was shown to possess the ability to produce corneal nerve stimulation either by surface deformation, temperature change, or both. Using thermal imaging equipment, a temperature drop in the ocular tear film was demonstrated that was localised, and limited to the cornea. A second series of experiments investigated the ability of the NCCA to measure a corneal sensitivity threshold. These studies indicated that a forced-choice, doublestaircase, Method of Limits experimental technique produced an accurate threshold, with low variability in the results, over a minimum time period. Further studies showed that this threshold measurement was repeatable to within 0.1 mbars. A database of typical normal sensitivity thresholds, under a number of physiological variables - corneal location, gender, age and iris colour, was developed. The results from these studies compared well qualitatively with those using invasive stimuli. A third series of experiments examined the ability of the NCCA to assess corneal nerve function when it was under a number of external influences. The first situation was that of anaesthesia,p roduced by 0.4% benoxinate hydrochloride. Non-contact corneal sensitivity loss and recovery were shown to return to normal levels 60mins after instillation of the anaesthetic. The second situation was that of long-term contact lens wear (i.e. longer than three years). Non-contact sensitivity was shown to be reduced with both soft and gas-permeable lens wear, although the extent of loss did not differ between them, nor was it influenced by the length of wear. Thirdly,corneal sensitivity loss and recovery was assessed in subjects following excimer laser photorefractive keratectomy (PRK). Three laser trials were completed: a longitudinal myopic study, a transverse myopic study, and a longitudinal hyperopic study. The results indicated that non-contact corneal sensitivity loss/recovery was not related to the attempted depth of ablation, and that sensitivity had still not returned to normal levels one year post-op.
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Makrynioti, Dimitra. "Variations in corneal morphology across the cornea : a study in normal subjects and contact lens wearers." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492043.

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Micali, Jason D., and John E. Greivenkamp. "Dual interferometer for dynamic measurement of corneal topography." SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 2016. http://hdl.handle.net/10150/622342.

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The cornea is the anterior most surface of the eye and plays a critical role in vision. A thin fluid layer, the tear film, coats the outer surface of the cornea and serves to protect, nourish, and lubricate the cornea. At the same time, the tear film is responsible for creating a smooth continuous surface, where the majority of refraction takes place in the eye. A significant component of vision quality is determined by the shape of the cornea and stability of the tear film. A dual interferometer system for measuring the dynamic corneal topography is designed, built, verified, and qualified by testing on human subjects. The system consists of two coaligned simultaneous phase-shifting polarization-splitting Twyman-Green interferometers. The primary interferometer measures the surface of the tear film while the secondary interferometer tracks the absolute position of the cornea, which provides enough information to reconstruct the absolute shape of the cornea. The results are high-resolution and high-accuracy surface topography measurements of the in vivo tear film and cornea that are captured at standard camera frame rates. (C) 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)
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Fisher, Damien. "The influence of scleral lens parameters and fitting characteristics on corneal oedema under open and closed eye conditions." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/211357/1/Damien_Fisher_Thesis.pdf.

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Scleral lenses are large rigid contact lenses used to treat diseases that affect the front surface of the eye. This thesis examined how scleral lens fitting characteristics can be optimised to reduce corneal tissue swelling. The results provide clinical guidance for contact lens practitioners and patients worldwide.
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Bastian, Philip Nathan Jr. "The Central and Peripheral Physiological Response of the Cornea to Three Hydrogel Contact Lens Diameters." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1337786341.

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Khan, Tahmina. "Investigation of the biological and chemical basis underpinning contact lens solution induced corneal staining." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/investigation-of-the-biological-and-chemical-basis-underpinning-contact-lens-solution-induced-corneal-staining(3d84a7c2-54d9-4c8f-92ad-4d4fa6134c07).html.

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Purpose: Sodium fluorescein ('fluorescein') is the most commonly used diagnostic ophthalmic dye for clinical assessment of the ocular surface. An increase in fluorescein staining presents after the use of certain multi-purpose solutions (MPS) and contact lenses, which is a clinical phenomenon known as solution induced corneal staining (SICS). The clinical relevance and mechanisms underpinning fluorescein staining however is conflicting in the literature. Currently a number of studies indicate fluorescein localises within cells that are healthy and metabolically active, in contrast to conventional thought that fluorescein staining of MPS treated cells is indicative of cellular toxicity; however the precise mechanism underpinning fluorescein internalisation is unknown. The aim of this doctoral thesis was thus to investigate novel biological mechanisms mediating fluorescein uptake and to determine the chemical inducers of increased fluorescein staining. Methods: Spectrofluorimetry was used to analyse the fluorescence intensity of various fluorescein solutions and of tear samples after fluorescein application to the ocular surface. For assessment of fluorescein uptake in cell cultures exposed to test MPS, fluorescence microscopy was performed; subsequently a high content analysis (HCA) microscopy methodology developed in this thesis, was used to enumerate fluorescein fluorescence intensity. The physiological state of cell cultures treated with a number of MPS and fluorescein were also assessed using propidium iodide (PI), Caspase-3 antibody for apoptosis analysis, metabolic activity assays and confocal microscopy. Endocytosis, macropinocytosis, and receptor-mediated uptake, mechanisms which previous to this work have not been investigated in association with SICS and fluorescein uptake, were studied using chemical inhibitors and serum starvation in cell culture, and then analysed by HCA. To study the hyperfluorescence inducing properties of MPS components, surfactant Tetronic 1107 (an MPS surfactant component typically overlooked and not investigated as an inducer of SICS) and Triton X-100 (a surfactant not found in MPS) were exposed to cell cultures and after fluorescein treatment, were analysed by HCA; metabolic activity assessment of identically treated cultures were also performed. Similarly, HCA and metabolic activity measurements were also performed in cell cultures treated with MPS biocides PHMB and Polyquaternium-1 (PQ-1). Results: Fluorescein fluorescence intensity was not affected by temperature, by alkali solvents, or by different MPS formulations; concentration remains the primary factor by which fluorescein intensity is affected. It was seen that after 1% w/v fluorescein instillation on the ocular surface, fluorescein concentration in tear samples significantly decreased within the first minute and decreased to as little as 0.0001% w/v after 10 minutes. Fluorescence microscopy and HCA techniques revealed that on treatment with Biotrue® (Bausch+Lomb, referred to as P-PQ1-1107) and ReNu Sensitive Multi-purpose Solution® (Bausch+Lomb, referred to as P-1107), fluorescein uptake increased in cell cultures, as typically seen clinically. Also typically seen clinically, cell cultures treated with Opti-free Replenish® (Alcon; PQ1-Aldox-1304) and Complete Revitalens® (AMO; PQ1-Alex-904) did not induce hyperfluorescence. Significantly, only those cells treated with PQ1-Aldox-1304 and PQ1-Alex-904 exhibited an increase in PI and loss of metabolic activity. Additionally, given that no significant Caspase-3 staining in all test MPS cells was seen by fluorescence microscopy and blebbing was only observed by confocal microscopy in P-PQ1-1107 treated cells, increased fluorescein hyperfluorescence is unlikely to be related to apoptosis. Study of various biological internalisation mechanisms revealed that dynamin (a protein associated with endocytosis) inhibition in P-PQ1-1107 or P-1107 treated cells significantly decreases fluorescein uptake with no detrimental effect to cell metabolic activity. Interestingly, on quantifying fluorescein uptake in surfactant treated cells, a significant increase in hyperfluorescence was measured with only Tetronic 1107 at concentration 1% w/v with no significant effect on cellular metabolic activity. In contrast, cell culture treatment with biocides PHMB, and PQ-1 did not induce increased fluorescein uptake comparable to MPS PPQ1-1107 or P-1107; metabolic activity assays revealed that this is likely attributed to the decrease in cell metabolic activity exhibited with these biocides. Conclusions: The differential fluorescein staining associated clinically with four varied MPS was also seen in an unique in vitro model, allowing the subsequent study of the SICS phenomenon and the fundamental basis of fluorescein uptake. Using this in vitro model, it was seen that fluorescein internalisation is associated with the protein dynamin in healthy, metabolically active cells, and is unlikely to be mediated by apoptosis. Moreover, fluorescein uptake is induced by surfactant Tetronic 1107 and not biocides PHMB or PQ-1, which is in contrast to the popular belief that increased hyperfluorescence is induced by the biocide component of MPS.
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9

Fink, Barbara A. "Quantifying the effects of contact lens prescription parameters on human corneal oxygen uptake /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487331541709205.

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Szczotka-Flynn, Loretta B. "The Longitudinal Analysis of Silicone Hydrogel Contact Lens Study." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1257182345.

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Books on the topic "Corneal lens"

1

1936-, Fine I. Howard, ed. Clear corneal lens surgery. Thorofare, NJ: SLACK Inc., 1999.

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Rouwen, A. J. P. Corneal alterations with contact lens wear. Amsterdam: Kugler Publications, 1992.

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Nathan, Efron, ed. The cornea: Its examination in contact lens practice. Oxford: Butterworth-Heinemann, 2001.

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A, Silbert Joel, ed. Anterior segment complications of contact lens wear. New York: Churchill Livingstone, 1994.

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Babizhayev, Mark A., David Wan-Cheng Li, Anne Kasus-Jacobi, Lepša Žorić, and Jorge L. Alió, eds. Studies on the Cornea and Lens. New York, NY: Springer New York, 2015. http://dx.doi.org/10.1007/978-1-4939-1935-2.

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S, Binder Perry, and New Orleans Academy of Ophthalmology. Session, eds. Cornea, refractive surgery, and contact lens. New York: Raven Press, 1987.

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D, Tomlinson Alan Ph, ed. Complications of contact lens wear. St. Louis: Mosby-Year Book, 1992.

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Hamano, Hikaru. The physiology of the cornea and contact lens applications. New York: Churchill Livingstone, 1987.

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Tantisira, Jivin Gerard. Comparison of precorneal tear film stability and basal tear secretion rates in contact lens wearers versus non-wearers. [s.n: s.l.], 1992.

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Anterior Segment Complications of Contact Lens Wear. 2nd ed. Butterworth-Heinemann, 2000.

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Book chapters on the topic "Corneal lens"

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Corbett, Melanie, Nicholas Maycock, Emanuel Rosen, and David O’Brart. "Contact Lens Practice." In Corneal Topography, 103–21. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-10696-6_7.

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Sharma, Vijay K., Nidhi Kalra, and Rajesh Sinha. "Contact Lens-Associated Emergencies." In Corneal Emergencies, 285–98. Singapore: Springer Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-5876-1_14.

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Lundergan, Maureen K. "The Corneascope-Comparator Method of Hard Contact Lens Fitting." In Corneal Topography, 117–28. New York, NY: Springer New York, 1992. http://dx.doi.org/10.1007/978-1-4612-2766-3_10.

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Hirnschall, Nino. "Surgically Induced Corneal Astigmatism." In Cataract and Lens Surgery, 185–90. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-05394-8_26.

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Daas, Loay, Elias Flockerzi, Shady Suffo, and Berthold Seitz. "Cataract Surgery for Corneal Pathologies." In Cataract and Lens Surgery, 509–19. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-05394-8_65.

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Aggarwal, Sneha, Nimmy Raj, Noopur Gupta, and Radhika Tandon. "Contact Lens-Related Corneal Infection and Inflammation." In Corneal Infection and Inflammation, 278–99. First edition. | Boca Raton, FL : CRC Press, 2021.: CRC Press, 2021. http://dx.doi.org/10.1201/9781003024897-26.

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Pedrosa, Catarina, and Filomena Ribeiro. "Reduction of Astigmatism by Corneal Incisions." In Cataract and Lens Surgery, 377–82. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-05394-8_50.

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Boden, Karl. "Corneal Incisions with the Femtosecond Laser." In Cataract and Lens Surgery, 759–64. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-05394-8_92.

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King, Gordon, and Roger Holmes. "Human Corneal and Lens Aldehyde Dehydrogenases." In Advances in Experimental Medicine and Biology, 19–27. Boston, MA: Springer US, 1996. http://dx.doi.org/10.1007/978-1-4615-5871-2_4.

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Kagokawa, Hiroyuki, Satoshi Ishiko, Norihiko Kitaya, Tohru Abiko, Fumihiko Mori, and Akitoshi Yoshida. "Corneal and Lens Autofluorescence in Myopia." In Myopia Updates, 383–87. Tokyo: Springer Japan, 1998. http://dx.doi.org/10.1007/978-4-431-66959-3_69.

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Conference papers on the topic "Corneal lens"

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Smith, George. "Spherical Aberration of the Crystalline Lens." In Vision Science and its Applications. Washington, D.C.: Optica Publishing Group, 1997. http://dx.doi.org/10.1364/vsia.1997.saa.2.

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Knowledge of the aberration properties of the lens are important for at least two reasons; (1) it gives some indication of the limitations of using corneal distortions alone as a measure of total ocular aberration and (2) it will help us unravel the gradient refractive index structure of the lens. In this paper we will use published data on ocular aberrations and corneal shape to estimate the spherical aberration of the lens. By comparing this data with predictions from equations for the spherical aberration of gradient index materials, we will examine possible forms of the gradient index structure of the lens.
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2

Weber, Timothy D., and Jerome Mertz. "High-resolution corneal and lens imaging with retroillumination microscopy." In Ophthalmic Technologies XXXI, edited by Daniel X. Hammer, Karen M. Joos, and Daniel V. Palanker. SPIE, 2021. http://dx.doi.org/10.1117/12.2578539.

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Klein, S. A., R. B. Mandell, and B. A. Barsky. "Representing corneal shape." In Vision Science and its Applications. Washington, D.C.: Optica Publishing Group, 1995. http://dx.doi.org/10.1364/vsia.1995.fc2.

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The power and radius expressions that are commonly used for corneal topography measurements are frequently misinterpreted. There is no consensus for the most appropriate expression of corneal topography, perhaps due to bias in the measurement process and misunderstanding of what is being measured. Agreement is needed as to the most appropriate methods for expressing corneal shape independent of the available measurement methods. This is a worthwhile enterprise since corneal shape measurements are useful in such applications as diagnosing corneal abnormalities, refractive corneal surgery and contact lens design.
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Lu, Yiming, Wentuo Yang, Yan Wang, Qian Fan, Xuexin Duan, and Mengying Xie. "Spiral Resonator-based Corneal Contact Lens For Intraocular Pressure Monitoring." In 2022 28th International Conference on Mechatronics and Machine Vision in Practice (M2VIP). IEEE, 2022. http://dx.doi.org/10.1109/m2vip55626.2022.10041067.

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Husinsky, W., S. Mitterer, G. Grabner, and I. Baumgartner. "Interaction of laser light with biological tissue-fundamental ablation processes and applications." In Microphysics of Surfaces, Beams, and Adsorbates. Washington, D.C.: Optica Publishing Group, 1989. http://dx.doi.org/10.1364/msba.1989.wc10.

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We have investigated the photo-ablation of human corneal tissue and and found effective, apparently non-conventional-thermal photoablation of human cornea by UV and non-UV-laserlight. Photo-ablation of polymers and human tissue by UV-laserlight has been extensively investigated in the last few years. Its potential application to laser surgery of the cornea has triggered a variety of investigations, comprising both, basic studies of the mechanisms of photoablation of biological-tissue as well as clinical applications for corneal or lens surgery.
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Raasch, Thomas W. "Quantitative Model of Corneal Astigmatism from Topographic Data." In Ophthalmic and Visual Optics. Washington, D.C.: Optica Publishing Group, 1992. http://dx.doi.org/10.1364/ovo.1992.wa3.

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Considerable attention in recent years has been directed towards the development of technology for the measurement of corneal topography. These developing techniques have significant applications in contact lens design and fitting, refractive manipulations of the cornea, and in the clinical and laboratory study of corneal diseases (Maguire and Bourne, 1989; McDonnell et al, 1989). There is a great deal of information contained in the typical representations of corneal data from commercial photokeratoscopes, and one of the more common presentation formats is a color coded map of corneal refractive power (Bogan et al, 1990; Maguire et al, 1987). This type of representation is useful, but quantitative representations of this information promise to enhance the utility of photokeratoscopy (Dingeldein et al, 1989). This paper describes a method for summarizing the information generated by photokeratoscopes. This method is particularly applicable to the description of astigmatism, and offers a new technique for conceptualizing and quantifying irregular astigmatism.
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Xu, David H., and Milton Katz. "Aspherized human schematic eye with GRIN crystalline lens." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oam.1991.tuww2.

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Blaker1 designed an adaptive human eye model with a gradient-index (GRIN) lens for zero and maximally accommodated states. His GRIN profiles were based on spherical corneal and lens surfaces. We present a computer modeled adaptive schematic eye with aspheric corneal and lens surfaces based on anatomical measurements and a GRIN lens. Our algorithm models up to 10 D of accommodation by continuously varying the axial and radial gradient indices; the anterior chamber and lens thicknesses; and the surface radii and conic constants of the lens. Spherical aberration and longitudinal chromatic aberration computed throughout the range of accommodation agree with empirical data. The astigmatic error of the model eye is compared with several empirical studies. Polychromatic MTFs at each level of accommodation and with pupil diameters of 2-8 mm are presented. We found that the NR1 radial gradient coefficient significantly impacts on paraxial power and can correct spherical aberration, the NR2, and NR3 and NR4 terms increase spherical aberration; and axial gradient terms higher than NZ2 have negligible effect on spherical aberration.
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Shimmick, John, and Charles Munnerlyn. "Corneal Analysis with a Rectilinear Photokeratoscope." In Ophthalmic and Visual Optics. Washington, D.C.: Optica Publishing Group, 1992. http://dx.doi.org/10.1364/ovo.1992.tuf1.

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Photorefractive keratectomy (PRK) involves precisely sculpting a lens on the anterior cornea by excimer laser photoablation (1). Consequently, patient positioning relative to the laser must be within certain predefined tolerance levels (2), and the procedure should be centered on the patient's line of sight (3).
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Klein, Stanley A., John Corzine, and Jonathan Kung. "Corneal topography volume maps for predicting rigid contact lens centration and motion." In Vision Science and its Applications. Washington, D.C.: Optica Publishing Group, 1998. http://dx.doi.org/10.1364/vsia.1998.ma.1.

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Khan, Salman N., and Panos S. Shiakolas. "To Understand Myopic Alleviation by Conducting Finite Element Structural Analysis of a Cornea With an Intrastromal Corneal Ring Implant." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51515.

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Myopia or shortsightedness is a visual impairment condition that is affecting more than 32 million Americans according to the American Academy of Ophthalmology, and this number is expected to increase even further with the increasing life expectancy in the United States. Myopia occurs when light rays entering the cornea are focused in front of the retina due to: high corneal curvature, short axial length of the eye, or high optical power of the natural lens. These reasons suggest that light refracting elements play a pivotal role in determining visual acuity. The cornea is the principal refractive element in the eye contributing almost 75 percent of ocular refractive power and if the shape of the cornea can be changed to increase or decrease the focal length of the converging light rays it could present a possible solution to improving myopia. The presented research focuses on the effects of intrastromal corneal ring (ICR) implantation on the shape of the cornea by developing a computationally efficient 3D axisymmetric finite element (FE) model of the cornea utilizing hyperelastic material properties. The results of the developed corneal FE model with a 360° ICR implant are analyzed and discussed. The FE model results provide confidence in the ability of the ICR implants to reduce myopia. The attained FE model results not only agree qualitatively with published clinical data but also provide a valuable insight into the surgery.
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Reports on the topic "Corneal lens"

1

Edwards, Jack R. A Study of Supersonic Compression-Corner Interactions using Hybrid LES/RANS Models. Fort Belvoir, VA: Defense Technical Information Center, January 2014. http://dx.doi.org/10.21236/ada605092.

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Laxmi Prasanna, Porandla, B. Anil kumar, and Macha Sahithi. A STUDY TO EVALUATE THE TEAR FILM CHANGES IN PATIENTS WITH PTERYGIUM. World Wide Journals, February 2023. http://dx.doi.org/10.36106/ijar/3408221.

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Introduction: Pterygium is a degenerative condition of the subconjunctival tissues which proliferate as vascularized granulation tissue to invade the cornea, destroying the supercial layers of the stroma and bowmans membrane, the whole being covered by conjunctival epithelium.The tear lm consists of three layers, the most supercial layer of tear lm is lipid layer produced by meibomian glands. The middle layer is the aqueous layer produced by the main lacrimal gland as well as accessory lacrimal glands of Krause and Wolfring. Aqueous layer constitutes over 90% of the tear lm. The layer closest to the cornea is the mucin layer produced by conjunctival goblet cells. Tear function abnormalities have been proposed as an etiologic factor for pterygium due to observation that a pterygium is exacerbated by dryness and dellen formation. Whether tear dysfunction is a precursor to pterygium growth or pterygium causes tear dysfunction is still not clear. The present study was taken up to study the tear lm changes in patients presenting with pterygium. Materials and methods: The present prospective study was conducted at the Department of Ophthalmology, Chalmeda Anand Rao Institute of Medical Sciences from Jan 2021- July 2022. 75 patients satisfying inclusion and exclusion criteria were included in the study. The eye with pterygium was considered as case and the normal eye of the same patient was considered as controls. The data was recorded for 150 eyes. All patients underwent visual acuity assessment, a detailed slit-lamp examination and ophthalmoscopy to rule out adnexal, anterior segment and posterior segment diseases. Patients were evaluated for tear lm changes using Schirmer's test(with anesthesia),Tear lm breakup time and Tear lm meniscus height. The mean age of the study population was 34.7±4.98 years, with 56% of ma Results: les and 44% of females. Pterygium was present in right eye in 73.33% (n=55) cases and 26.66% (n=20) had it in the left eye. All were on the nasal conjunctiva. Schirmer's test was signicantly lower in eyes with pterygium with P value of <0.001. Tear Film Break Up time and Tear Film meniscus height was signicantly lesser in the eyes with pterygium with P=<0.001. From the present study, we ca Conclusion: n suggest that unstable tear lm is found to a greater extent in eyes with pterygium than in eyes without pterygium. Pterygium is one of the most common ocular surface disorders which results in instability of tear lm indices and thus lead to dysfunctional tear lm and development of dry eye.
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Mballa, Charles, Josephine Ngebeh, Machtelt De Vriese, Katie Drew, Abigayil Parr, and Chi-Chi Undie. Pratiques du HCR et de ses partenaires en matière de protection communautaire dans les secteurs dans la région de l’Afrique de l’Est, de la Corne de l’Afrique et des Grands Lacs. Population Council, 2020. http://dx.doi.org/10.31899/rh14.1053.

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