Intraocular Telescopic System Design: Optical and Visual Simulation in a Human Eye Model

Purpose. To design an intraocular telescopic system (ITS) for magnifying retinal image and to simulate its optical and visual performance after implantation in a human eye model. Methods. Design and simulation were carried out with a ray-tracing and optical design software. Two different ITS were designed, and their visual performance was simulated using the Liou-Brennan eye model. The difference between the ITS was their lenses’ placement in the eye model and their powers. Ray tracing in both centered and decentered situations was carried out for both ITS while visual Strehl ratio (VSOTF) was computed using custom-made MATLAB code. Results. The results show that between 0.4 and 0.8 mm of decentration, the VSOTF does not change much either for far or near target distances. The image projection for these decentrations is in the parafoveal zone, and the quality of the image projected is quite similar. Conclusion. Both systems display similar quality while they differ in size; therefore, the choice between them would need to take into account specific parameters from the patient’s eye. Quality does not change too much between 0.4 and 0.8 mm of decentration for either system which gives flexibility to the clinician to adjust decentration to avoid areas of retinal damage

Age-related changes in the human visual system and prevalence of refractive conditions in patients attending an eye clinic

PURPOSE: To retrospectively report the trends of change in several parameters of the human visualsystem over a wide age range in patients attending an eye clinic. SETTING: University of Valencia, Valencia, Spain. METHODS: The clinical records of 2654 patients were retrospectively reviewed, and the age, sex, spherocylindrical refraction, visual acuity, keratometry, and intraocular pressure were obtained. Descriptive values for each parameter and the correlations with age and between different parameters were calculated. Vectorial components of refraction, including blur, were also derived from clinical refractive data and then analyzed. RESULTS: Several parameters changed significantly with age, particularly in patients in their sixties and older. An increase in the blur component was mainly associated with astigmatic progression and a trend toward against-the-rule orientation and had the highest correlation with total astigmatism (r2=0.319; P<.001) and visual acuity (r2=0.442; P<.001). Refractive conditions had the most homogeneous distribution in the first decade of life and the most heterogeneous distribution in the group between 61 years and 70 years. CONCLUSIONS: Best corrected visual acuity began to decrease after the 50s, while changes in the blur component were not patent until the 60s to 70s. This could be explained by the poorer optical quality of the human eye in adulthood and elderly persons. Clinically, these changes could be attributed to changes in ocular astigmatism and have an impact on the best visual acuity achievable with optical compensatio

Artiflex Toric Phakic Intraocular Lens Implantation in Congenital Nystagmus

Case: A 44-year-old woman with congenital nystagmus and myopic astigmatism in both eyes who was submitted to phakic intraocular lens (pIOL) implantation. Methods: Full ophthalmologic examination including refractive status, corrected (CDVA) and uncorrected (UCVA) monocular and binocular visual acuities, ocular motility, slit-lamp evaluation, tonometry and fundoscopy before and after implantation of toric pIOLs (Artiflex; Ophtec BV, The Netherlands) in both eyes. Results: Preoperative logMAR CDVA were 0.699 and 0.420 in the right and left eye, respectively. Three months after surgery, logMAR UCVA were 0.398 and 0.182, reaching binocular logMAR UCVA of 0.132. There were no changes in nystagmus characteristics after surgery. Conclusions: pIOL implantation may be a safe and suitable treatment to correct high refractive errors in patients with congenital nystagmus. Significant improvement in CDVA and UCVA can be achieved

Accommodative Stimulus-Response Curve with Emoji Symbols

Purpose. To evaluate the static measurement of the accommodative stimulus-response curve with emoji symbols. Methods. The accommodative stimulus-response curve was measured in 18 subjects using a Hartmann-Shack sensor to obtain the objective accommodative response from the Zernike defocus term. Measurements were acquired at different accommodative demands, from 0 to 3 D with a step of 0.5 D. Detailed and nondetailed emoji targets were used with two different sizes, corresponding to the two most common visual angles used in smartphones. Results. A regression analysis was performed to fit the mean results obtained for each target. The determination coefficient was R2≥0.988 for all targets. For the detailed targets, the slopes for the averaged stimulus-response curve were 0.65 and 0.66 for the bigger and smaller sizes, respectively. For the nondetailed targets, the slopes were 0.60 and 0.58 for the bigger and smaller sizes, respectively. p values for these slopes were statistically significant for the two types of targets (p<0.01). Conclusions. Our results reveal that the replacement of a word or several words by detailed or nondetailed emoji symbols seems not to provoke a different accommodative response in normal subjects and under standard viewing conditions in the use of smartphones

Retinal straylight and light distortion phenomena in normal and post-LASIK eyes

Purpose To assess the relationship between measures of light distortion and retinal straylight in normal and post- LASIK subjects. Design Cross-sectional, non-randomized, masked observational case series Setting Clinica Oftalmologica Novovision, Madrid, Spain. Methods Thirty eyes from 30 healthy subjects (mean age 33.9±8.3 years old; mean spherical equivalent (MSE) −2.06± 1.40 D) and thirty six eyes from thirty six refractive surgery patients (mean age 36.1±7.7 years old; mean preop MSE −3.43±2.23 D) were examined with the Starlights and the C-Quant straylightmeter in a case-control study. Results The age of both treated and control groups was not statistically different (p>0.05). Statistically significant differences between controls and post-LASIK eyes were found for luminous distortion index (LDI), but not for retinal straylight. Correlation analysis yielded significant correlation between retinal straylight Log(s) values and BCVA measures (r=0.379, p=0.002). Control subjects showed significant correlation between MSE and retinal straylight Log(s) values (r=-0.650, p<0.001), while post-LASIK eyes showed a significant correlation between LDI and Log(s) values (r= 0.338, p=0.044) and between Log(s) values and BCVA (r= 0.460, p=0.005). Correlation between measures obtained by both methods was higher after LASIK than in control eyes, although values were quite scattered in any case. Conclusion Light distortion phenomena and retinal straylight measures are correlated in both normal and postsurgical eyes. Both parameters are increased in LASIK subjects compared to control non-operated subjects.This research was supported in part by a Universitat de Valencia Research Grant (#UV-AE-08-2291#) and a Ministry of Science and Innovation of Spain (#JC2008-00078) to Alejandro Cervino, from the Fundacao para a Ciencia e Tecnologia of Portugal through a Grant to Jose Manuel Gonzalez-Meijome (#PTDC/SAU-BEB/098392/2008#), and from the Ministry of Science and Innovation of Spain (Red Tematica de Investigacion en Optometria, SAF2008-01114-E)

Implantable collamer posterior chamber intraocular lenses : a review of potential complications

Artigo submetidoPURPOSE: To review the peer-reviewed literature reporting pstoperative complications of the most recent models of Visian Implantable Collamer posterior chamber intraocular lenses (ICL, STAAR Surgical Co). METHODS: A literature search of the PubMed database was performed to identify all articles related to ICL complications. Articles were obtained and reviewed to identify those that reported complications using the latest ICL designs. RESULTS: Cataract was the major postoperative complication reported: 136 (5.2%) in 2592 eyes. Of those, 43.4% (n=59) were reported within 1 year, 15.4% (n=21) between 1 and 3 years, and 35.3% (n=48) >3 years after ICL implantation. Twenty-one (15.4%) cataracts were reported as surgically induced, 46 (33.8%) eyes had poor vault (,200 μm), and cataract surgery was carried out in 27.9% (n=38) of eyes. Early acute intraocular pressure increase was also reported to be relatively frequent, whereas acute pupillary block was less frequent and mostly resolved with additional iridotomies. A total of 42 ICLs were explanted due to cataract and IOP. Reported endothelial cell loss varied from 9.9% at 2 years to 3.7% 4 years postoperatively. This loss was reported to be more pronounced within the fi rst 1 to 2 years, with stability or lower progression after that time. CONCLUSIONS: The majority of reported complications after ICL implantation are cataract formation. The improvements in lens geometry and more accurate nomograms applied to the selection of the lens to be implanted, in addition to the surgeon’s learning curve, might be factors in the decreased occurrence of postoperative complications reported currently.Ministerio de Ciencia e Innovación Research Grants to Dr Montés-Micó (#SAF2008-01114-E# and #SAF2009- 13342#) and Fundação para a Ciência e Tecnologi

“In situ” corneal and contact lens thickness changes with high resolution OCT

Purpose: To show the utility of high resolution spectral domain optical coherence tomography (HR SOCT) for the in situ evaluation of epithelial, stromal and contact lens (CL) thickness changes under closed-eye conditions without lens removal. Settings: Clinical and Experimental Optometry Research Lab, University of Minho, Portugal. Methods: Eight young healthy patients wore a thick soft CL during 90 minutes under closed-eye conditions and measures of epithelial and stromal corneal thickness were obtained at regular intervals using a HR SOCT (Copernicus HR, Optopol Tech. SA, Poland). Results: Minimal changes in epithelial thickness were detected with a transient statistically significant increase in epithelial thickness in the fellow control eye 30 minutes after insertion (p=0.028). A significant and progressive increase in stromal thickness up to 8% after 90 minutes of lens wear was observed at a constant rate of 2.5% 50 every 30 minutes, being statistically significant in all observations (p<0.001). Fellow control eye also showed a significant increase in stromal thickness at a much lower rate of 0.5% every 30 minutes. Lens thickness decreased significantly by 2% after 90 minutes of lens wear under closed eye conditions (p<0.001). Individual analysis showed that all eyes displayed stromal swelling, while only half of them showed epithelial swelling. Conclusion: Increase in stromal thickness and a slight decrease in lens thickness were observed in response to a hypoxic stimulus under closed eye conditions. High resolution spectral domain HR SOCT is a powerful tool to investigate in vivo the physiological interactions between cornea and contact lenses.Supported in part by research grants to A. Cervino from the Universitat de Valencia (UV-AE-20070225), the "Jose Castillejo" Research Grant from the Spanish Ministry of Science and Technology (JC2008-00078) and the Spanish Network for Research in Optometry (SAF2008-01114-E)

Intrasession and Intersession Repeatability of a new PCT-200 Corneal Topographer on Calibrated Steel Surfaces and Healthy Eyes

PURPOSE: To assess intrasession and intersession repeatability of a new tilted-cone, Placido-disc based corneal topographer (PCT-200, Optopol Tech., Poland) on calibrated steel surfaces and healthy human eyes. METHODS: Five repeated measures of surface topography were obtained on a set of four different calibrated steel spherical surfaces and on a sample 30 healthy human eyes in each of two sessions. Variance of apical radius, eccentricity and Fourier Indices was assessed both within and between sessions using analysis of variance (ANOVA), paired samples t-test and intraclass correlation coefficients (ICC). RESULTS: Repeated measurements on calibrated steel surfaces and human eye sample of all parameters were not significantly different within session (ANOVA) nor between sessions (paired samples t-test), p-values exceeded greatly 0.05 in all cases. ICCs were greater than 0.98 and 0.77 for steel surfaces and human eyes, respectively, for all parameters analysed. CONCLUSIONS: The new tilted-cone corneal topographer performs well in both spherical surfaces and healthy human eyes, providing with repeatable measures of corneal topography, comparable to other Placido-based devices currently in the market

Prevalence of refractive conditions in the general population attending eye care clinics in the north of Portugal

The purpose of this study was to report the fi rst estimations on the prevalence of refractive conditions in a Portuguese population attending several ophthalmologic and optometric clinics within the same region. Methods: Values of non-cycloplegic subjective refraction from the right eye of 4288 patients (40.08±18.75 years) were analyzed to estimate the prevalence of refractive conditions as a function of age and gender. The prevalence of anisometropia and presbyopic correction as a function of age and gender were also investigated. Results: Mean spherical equivalent refractive error was –0.29±2.01D. 29.8% of the patients had myopia, 45% had emmetropia and 25.2% had hyperopia. Young adults ranging from 20 to 35 years of age presented the highest prevalence of myopia. Conversely, the peak of hyperopic condition was for the oldest population. Anisometropia, defi ned as a difference in spherical equivalent equal or higher than 3D was present in 1.4% of our population. Conclusion: The prevalence of refractive conditions has been established for a large non-randomized sample of the Portuguese population for the fi rst time. Important refractive changes were evidenced in the fi fth decade of life, comprising an increase in the prevalence of hyperopia along with a shift in the amount of astigmatism. Although this study is not representative of the overall Portuguese population, there seem to be evidence that myopia could be increasing among the younger age groups