Loss Of Contrast Sensitivity Research Articles

Estudio longitudinal de la función visual en pacientes con esclerosis múltiple remitente-recurrente con y sin antecedentes de neuritis óptica

IntroductionThe contrast sensitivity test determines the quality of visual function in patients with multiple sclerosis (MS). The purpose of this study is to analyse changes in visual function in patients with relapsing-remitting MS with and without a history of optic neuritis (ON). MethodsWe conducted a longitudinal study including 61 patients classified into 3 groups as follows: a) disease-free patients (control group); b) patients with MS and no history of ON; and c) patients with MS and a history of unilateral ON. All patients underwent baseline and 6-year follow-up ophthalmologic examinations, which included visual acuity and monocular and binocular Pelli-Robson contrast sensitivity tests. ResultsMonocular contrast sensitivity was significantly lower in MS patients with and without a history of ON than in controls both at baseline (P=.00 and P=.01, respectively) and at 6 years (P=.01 and P=.02). Patients with MS and no history of ON remained stable throughout follow-up whereas those with a history of ON displayed a significant loss of contrast sensitivity (P=.01). Visual acuity and binocular contrast sensitivity at baseline and at 6 years was significantly lower in the group of patients with a history of ON than in the control group (P=.003 and P=.002 vs P=.006 and P=.005) and the group with no history of ON (P=.04 and P=.038 vs P=.008 and P=.01). However, no significant differences were found in follow-up results (P=.1 and P=.5). ConclusionsMonocular Pelli-Robson contrast sensitivity test may be used to detect changes in visual function in patients with ON.

Assessment of contrast sensitivity loss after intrastromal femtosecond laser and LASIK procedure.

To assess the loss of contrast sensitivity (CS) function for INTRACOR or intrastromal femtosecond laser presbyopia procedure to conventional LASIK procedures. Patients were recruited from a refractive surgery center for either INTRACOR or conventional LASIK. INTRACOR was performed on 8 eyes and LASIK was performed for 40 eyes in an overlapping period. Pre-operative evaluation and post-operative follow up for up to three months was done. Drops of CS in 4 spatial frequency (3 cpd, 6 cpd, 12 cpd and 18 cpd) right before and 3mo after the surgery were compared by Wilcoxon signed ranks test. For INTRACOR, CS threshold showed significant drop at both glare and non-glare condition, the drop was seen in all 4 spatial frequency. The averaged loss over the 4 spatial frequencies 3mo after surgery was 1.18 for non-glare and 0.71 for glare. For LASIK the CS threshold drop was most significant in 12 cpd for glare. INTRACOR procedure produces a gain of near vision for presbyopia patients but also introduces a high lost of contrast sensitivity plus worsen of vision quality. Pre-surgical patient selection and advise should be given with specific regards to night driving and glare conditions.

Does Retinal Neurodegeneration Seen in Diabetic Patients Begin in the Insulin Resistance Stage?

Objectives: To investigate whether retinal neurodegeneration and impairment in contrast sensitivity (CS), which have been demonstrated to begin in diabetic patients before the presence of signs of diabetic retinal vasculopathy, also occur in the stage of insulin resistance.Materials and Methods: The average, minimum and sectoral (inferior, superior, inferonasal, superonasal, inferotemporal and superotemporal) thicknesses of the ganglion cell-inner plexiform layer (GCIPL) measured using optical coherence tomography were compared between an insulin-resistant group and control group in order to evaluate the presence of retinal neurodegeneration. The CS of the two groups was also compared according to the logarithmic values measured at spatial frequencies of 1.5, 3, 6, 12 and 18 cycles per degree in photopic light using functional acuity contrast test (FACT).Results:Twenty-five eyes of 25 patients with insulin resistance (insulin resistant group) and 25 eyes of 25 healthy subjects (control group) were included in this study. There were no statistically significant differences between the two groups in any of the spatial frequencies in the FACT. The mean average GCIPL thickness and mean GCIPL thickness in the inferotemporal sector were significantly less in the insulin-resistant group when compared with the control group (mean average GCIPL thicknesses in the insulin-resistant and control groups were 83.6±4.7 µm and 86.7±3.7 µm respectively, p=0.01; mean inferotemporal GCIPL thicknesses in the insulin-resistant and control groups were 83±6.0 µm and 86.7±4.6 µm respectively, p=0.02).Conclusion: Although it may not lead to functional visual impairment such as CS loss, the retinal neurodegeneration seen in diabetic patients may begin in the insulin resistance stage.

Contrast Sensitivity Change– A Tool of Monitoring Glaucoma Progression

Introduction: Glaucoma is a potentially blinding disease,causing gradual loss of sight. It is often associated with increased intraocular pressure that can damage the optic nerve, which transmits images to the brain. Glaucoma can lead to permanent vision loss, if the damage continues. Without treatment, glaucoma can cause total permanent blindness within a few years. Glaucoma is one of the major causes of ocular morbidity and primary open–angle glaucoma is a major health problem. The prevalence of primary open- angle glaucoma (POAG) is estimated as being from 1.1-3% of western populations, over the age of 40 years, in both past and more recent population surveys.
 Objective: To evaluate and compare the value of Contrast sensitivity (CS) and automated perimetry among primary open-angle glaucoma (POAG) patients, glaucoma suspects and normal control.
 Materials and Methods: It was a prospective observational hospital based study conducted in National Institute of Ophthalmology & Hospital (NIO&H), Dhaka during the period from January 2006 to December 2006. A total of 30 POAG patients, 30 glaucoma suspects and 30 normal control subjects were recruited for the study. After complete baseline evaluation, all the study subjects underwent visual field assessment by Octopus automated field analyzer and CS evaluation by Low Contrast Flip Chart. Outcome measures were baseline CS of POAG patients, glaucoma suspects and normal controls, mean CS of POAG patients at 3 months after treatment, baseline MS of POAG patients, glaucoma suspects and normal controls in Octopus perimetry and retinal mean sensitivity (MS) of POAG patients 3 months after treatment.
 Results: Among the POAG patients MS was 22.23 dB, among glaucoma suspects MS was 27.50 dB and among normal controls mean MS was 30.0 dB; among the POAG patients mean CS was 2.99% whereas it was 2.20% and 1.41% respectively among glaucoma suspects and normal controls. Baseline CS had negative correlation with MS among POAG patients (correlation co-efficient, r = -0.908). It indicates that better CS is associated with higher MS. Out of 30 cases of POAG, 20 (66.67%) received medical and 10 (33.33%) received surgical treatment. Mean CS improves to 2.66% from baseline 2.99% after treatment and MS improves to 23.16 dB from base 22.23 dB after treatment. Correlation after three months of treatment was significantly negative (r = -0.86).
 Conclusion: As increased loss of MS of perimetry has been found to be associated with increased loss of CS, assessment of CS may become an easy, convenient tool for glaucoma diagnosis.
 Journal of Armed Forces Medical College Bangladesh Vol.12(2) 2016: 90-92

Degradation of Visual Performance With Increasing Levels of Retinal Stray Light.

To quantify the effect of induced stray light on halo size, luminance threshold, and contrast sensitivity. Retinal stray light was induced in five healthy subjects using different photographic filters. The stray light induced ranged from levels observed in intraocular lenses (IOLs) with glistenings (low) to cataract level (high). The visual impact was measured for halo size, luminance detection threshold, and contrast sensitivity with and without a glare source. The amount of retinal stray light induced by the different filters was similar when measured using the psychophysical method and the optical bench method. Low amounts of induced stray light cause the halo size to increase by 21%, the luminance detection threshold to increase by 156%, and contrast sensitivity to decrease by 10% to 21% dependent on spatial frequency and presence of a glare source. The visual impact percentages for high amounts of induced stray light were, respectively, 76%, 2130%, and 30% to 49%. In the presence of a glare source, contrast sensitivity losses were larger and shifted to lower spatial frequencies. Low levels of retinal stray light can cause significant increases in halo sizes, elevations in luminance detection thresholds, and reductions in contrast sensitivity whether or not a glare source is present.

Efficacy of Primary Posterior Curvilinear Capsulorhexis in Adults

Posterior capsular opacification(pco) is the most frequent complication of cataract surgery anddevelops from residual lens epithelial cells that undergo proliferation,migration,metaplasia and differentiation in the capsular bag after cataract surgery.patients with PCO have decreased visual visual acuity, loss of contrast sensitivity, and in some cases, PCO precludes examination of the posterior segment. The incidence of PCO is reported to be 20-50% 5 years after cataract surgery in the general population and has been reported to occur in 100% of pediatric patients. Recently, primary posterior capsulorhexis (PPCC) has been proposed to prevent PCO in adults. The PPCC technique is frequently used in children with or without anterior vitrectomyto prevent posterior capsule opacification (PCO) but is rarely used in adults. In PPCC, the central portion of the posterior capsule is removed during cataract surgery to prevent equatorial LEC migration toward the visual axis. Aim: The aim of the current study was to report the long-term efficacy and safety of phacoemulsification and manual phaco with posterior chamber intra ocular lens implantation combined with PPCC in adult patients with cataract. Materials And Methods: In an interventional case series 100 patients underwent cataract surgery combined with PPCC at Rajiv Gandhi Institute of Medical Sciences Kadapa, Andhra Pradesh from August 2014 to June 2016. Informed consent was obtained from all patients preoperatively. Only adult patients who underwent cataract surgery and PPCC for age-related cataract were included the study. Inclusion Criteria: Although we do not routinely perform PPCC during cataract surgery in adults, it is performed for cases with residual posterior capsule opacification despite careful polishing. Excleusion Criteria: Patients with glaucoma, uveitis, zonular weakness, and proliferative diabetic retinopathy were excluded in this study. Patients with clear posterior capsule were also excluded. Keywords:posterior capsular opacification, Nd: YAG capsulotomy, phacoemulsification, manualphaco, intra ocular lens, and primary posterior capsulorhexis

Effects of Chronic and Acute Intraocular Pressure Elevation on Scotopic and Photopic Contrast Sensitivity in Mice.

PurposeTo compare the impact of intraocular pressure (IOP) elevation on scotopic and photopic contrast sensitivity in mice.MethodsWe chronically elevated the IOP of wild-type mice via injection of polystyrene beads or acutely via injection of highly cohesive sodium hyaluronate. Some eyes with chronically elevated IOP were treated with either topical brimonidine tartrate 0.1% or brinzolamide 1%. Scotopic and photopic contrast sensitivity was assessed at peak spatiotemporal frequencies at multiple time points, with an established optokinetic technique. Retinal ganglion cell (RGC) counts were determined with an antibody to class III beta-tubulin. Correlations among IOP level, RGC count, and scotopic or photopic contrast sensitivity were performed.ResultsSix weeks of IOP elevation caused a generalized reduction of photopic contrast sensitivity and a preferential reduction of scotopic contrast sensitivity at peak spatiotemporal frequencies. The administration of brinzolamide but not brimonidine caused a significant reduction in cumulative IOP, whereas brimonidine, but not brinzolamide, prevented RGC loss. Both brimonidine and brinzolamide prevented contrast sensitivity loss, but brimonidine did so at earlier time points and across a wider range of lighting conditions. Following either chronic or acute IOP elevation, scotopic contrast sensitivity was impacted most prominently by IOP level and not by RGC count, while photopic contrast sensitivity was impacted by a combination of factors.ConclusionsIt is possible that scotopic-specific retinal circuitry is altered preferentially by IOP elevation, and that changes in scotopic contrast sensitivity will assist with glaucoma detection. Brimonidine appears to prevent RGC loss via an IOP-independent mechanism.

Treatment of Presbyopia in Emmetropes Using a Shape-Changing Corneal Inlay: One-Year Clinical Outcomes

To report 1-year safety and efficacy clinical outcomes of a shape-changing corneal inlay for the treatment of presbyopia. Prospective, nonrandomized, multicenter United States Food and Drug Administration Investigational Device Exemption clinical trial (clinicaltrials.gov identifier, NCT01373580). Nondominant eyes (N = 373) of emmetropic presbyopic subjects were implanted at 11 sites with the Raindrop Near Vision Inlay (ReVision Optics, Lake Forest, CA); 340 eyes underwent the 1-year follow-up visit. The corneal inlay was implanted under a corneal flap at the center of the light-constricted pupil created with a femtosecond laser. For subjects completing the 1-year follow-up, monocular and binocular uncorrected and corrected visual acuity, refractive stability, contrast sensitivity (CS; photopic and mesopic), symptom and satisfaction questionnaire results, and adverse events. At 1 year in the treated eye, on average, uncorrected near visual acuity (UNVA) improved by 5.1 lines, uncorrected intermediate visual acuity (UIVA) improved by 2.5 lines, and uncorrected distance visual acuity (UDVA) decreased by 1.2 lines. From 3 months through 1 year, 93% of subjects achieved UNVA of 20/25 or better, 97% achieve UIVA of 20/32 or better, and 95% achieved UDVA of 20/40 or better. Binocularly, the mean UDVA exceeded 20/20 from 3 months through 1 year. Contrast sensitivity loss occurred only at the highest spatial frequencies, with no loss binocularly. Absent or mild scores were reported in 96% of subjects for visual symptoms (glare, halos, double vision, and fluctuations in vision), in 99% for ocular symptoms (pain, light sensitivity, and discomfort), and in 95% for dryness. Adverse events were treatable and resolved. Eighteen inlays were replaced, usually soon after implantation because of decentration, but UNVA was little affected in this group thereafter. In the 11 cases requiring inlay explantations, 100% achieved a corrected distance visual acuity of 20/25 or better by 3 months after explant. The Raindrop Near Vision Inlay provides significant improvement in near and intermediate visual performance, with no significant change in binocular distance vision or CS. Subject satisfaction is improved significantly with minimal ocular or visual symptoms.

Straylight and Visual Quality on Early Nuclear and Posterior Subcapsular Cataracts

ABSTRACTPurpose: To measure log(s) and OSI parameters, both related to forward light scattering in the eye, in subjects with different kinds of early cataracts—nuclear or posterior subcapsular—and corrected visual acuity (CVA).Methods: 34 eyes of 19 patients ranged between 50 and 75 years old with diagnosed nuclear (14 eyes) or posterior subcapsular cataract (20 eyes) were recruited. Only NO1, NO2, P1, and P2 opacity scores according to LOCS III were included. Observer examination included visual acuity, contrast threshold (Ct), and measurements performed by straylightmeter (straylight parameter log(s)) and double-pass instrument (objective scatter index (OSI)).Results: OSI and log(s) were correlated with LOCSIII in nuclear opacities (p = 0.015 and 0.004, respectively) and in the whole data (p = 0.027 and 0.019, respectively) but did not for posterior subcapsular opacities alone. OSI was strongly correlated with log(s) in nuclear (r = 0.885 and p < 0.001) but not in posterior subcapsular cases (r = 0.382 and p = 0.097). Ct was correlated with log(s) for both cataract types (p = 0.043 for nuclear and p= 0.005 for posterior subcapsular cataract) but not with OSI (p = 0.093 for nuclear and p = 0.064 for posterior subcapsular cataract).Conclusions: OSI and log(s) discriminate early stages of nuclear cataracts when taking LOCS III as reference, so these opacities could be graded by any of those parameters. LOCSIII does not represent the visual condition for posterior subcapsular cataract. Straylightmeter measurements express the loss in contrast sensitivity caused by nuclear and posterior subcapsular opacities. Studies of lens opacities must be separated according to the type of opacity present in eyes.

A study of incidence of posterior capsular opacification after cataract surgery with square edge PMMA intra ocular lens

Introduction: PCO usually leads to a decrease in visual acuity (VA), glare disability and a loss of contrast sensitivity. It has been reported earlier that sharp edge intraocular lens optics are better than rounded edge IOL optics. This study was performed to identify the incidence of Posterior capsular opacification after a cataract surgery with square edge IOLs. Materials and Methods: 75 patients with Senile cataract –irrespective of grade &type, between the ages of 40 – 80 years who underwent cataract surgery were included in this study. The cataract surgery was conducted and square edge IOLs was places within the capsular bag. Signs for PCO was observed during one year of follow-up. Results: The most common type of cataract in our study was mature senile cortical cataract, seen in 23 (28%) of the patients. Post-operative course was uneventful in 64 patients (85.33%). 3 patient(4%) had mild iritis and 8(10.67%) patients were noted with minimal corneal edema at first post-operative day and resolved in the next week with topical medications. capsule opacification was seen in 5 of the 75 patients (6.67%). 2 of the 5 patietns had fibrous membrane type and 3 developed Elsching’s pearl type of PCO. Conclusion: The design of IOLs specially the one with square edge plays a major role in preventing posterior capsule opacification especially in the elderly with a very good visual outcome. Keywords: Posterior capsular opacifications, Intraocular lens, Cataract surgery

The changes of the retinal layers in diabetic patients without retinopathy

SummaryDiabetic retinopathy is considered to be a neurovascular disease. But in fact, retinal neurodegeneration is present before any microcirculatory abnormalities can be detected in ophthalmoscopic examination. We know this from functional studies documenting electroretinogram abnormalities, loss of dark adaptation, contrast sensitivity and color vision and abnormal microperimetry occur before any vascular abnormality is detected. Novel imaging devices have allowed this pre‐vascular damage to be quantified in a non‐invasive and reproducible way using spectral domain optical coherence tomography (SD‐OCT) that allows in vivo retinal layer thickness measurement. The extent to which this new technology can be used in the clinical setting for early screening in diabetic retinopathy will be the focus of this lecture. The review of the state of the art in this exciting new field of study may prove valuable in the management of this condition.

Neuroretinal Degeneration in HIV Patients Without Opportunistic Ocular Infections in the cART Era

Subtle structural and functional retinal abnormalities, termed 'HIV-associated Neuroretinal Disorder (HIV-NRD)', have been reported in HIV patients receiving combination antiretroviral therapy (cART), without infectious retinitis or any apparent fundus abnormalities otherwise. In this review, we provide an overview of studies investigating HIV-NRD in HIV patients without opportunistic ocular infections in the cART era, and try to elucidate underlying mechanisms and associated risk factors. Most studies focused on patients with severe immune-deficiency and demonstrated that patients with nadir CD4 counts<100 cells/μL are most at risk for neuroretinal damage, with a thinner retinal nerve fiber layer, subtle loss of color vision and/or contrast sensitivity, visual field deficits, and subnormal electrophysiological responses. In contrast, alterations in retinal vascular calibers and retinal blood flow were not associated with nadir CD4 counts, but instead with detectable viremia, suggesting a role for (chronic) inflammation in microvascular damage. Although the alterations in visual function are subtle, they can lead to difficulties in activities, such as reading or driving, thereby affecting quality of life. Since HIV has become a chronic disease, its long-term effects with respect to visual function loss become more important, as is recently emphasized by a longitudinal study, reporting that AIDS patients with HIV-NRD have higher risks of developing bilateral visual impairment and even blindness than patients without HIV-NRD. The question remains whether patients with high (>350 cells/μL) nadir CD4 counts and well-suppressed HIV infection on cART remain at risk for HIV-NRD, as this group constitutes a growing part of the aging HIV-infected population.

A Novel Motion-on-Color Paradigm for Isolating Magnocellular Pathway Function in Preperimetric Glaucoma.

This study investigated a novel motion-on-color paradigm to functionally isolate the magnocellular pathway and evaluate its diagnostic value in preperimetric glaucoma patients. Thirty patients with preperimetric primary open-angle glaucoma and 30 controls participated in this study. They were tested in both the foveal and peripheral locations. Contrast sensitivity was assessed for the direction discrimination of a moving luminance-modulated grating presented on top of a red/green isoluminant grating. The moving test grating was designed to target the magnocellular pathway, while the background red/green isoluminant grating was designed to saturate the parvocellular pathway. The luminance-modulated grating was presented at spatial frequency of 0.5 cyc/deg, moving horizontally at four temporal frequencies (3 Hz, 8 Hz, 15 Hz, 25 Hz). Participants were asked to indicate the direction of motion for the luminance grating. As a comparison condition, frequency-doubling stimuli were also presented in the periphery and participants were asked to detect the occurrence of the frequency-doubled pattern. Two-way repeated-measures analysis of variance was performed with temporal frequency modulations as within-subject factor and group as between-subject factor, while contrast sensitivity was the dependent variable. Receiver operating characteristic (ROC) analysis was used to characterize diagnostic performance of the new procedure in comparison with the frequency-doubling tests for preperimetric glaucoma. The contrast sensitivity function in both the fovea and the periphery showed an inverted "V" shape with highest sensitivity in the intermediate temporal frequencies, consistent with physiological properties of the magnocellular pathway. At the fovea, compared to the control group, the sensitivity for the glaucoma patients was slightly but not significantly reduced (P > 0.05), and there was no significant interaction between groups and temporal frequency (P > 0.05). In the periphery, patients' sensitivity was significantly lower (P < 0.001) than that of normal participants, especially in high temporal frequencies, as supported by a statistically significant interaction between groups and temporal frequency (P < 0.001). The areas under ROC curves (AUROC) obtained for the motion-on-color paradigm in the periphery were 0.957 (25 Hz), 0.870 (15 Hz), 0.758 (8 Hz), and 0.561 (3 Hz) and were 0.761 for the traditional frequency-doubling test. The motion-on-color paradigm revealed a loss of contrast sensitivity in the peripheral visual field in preperimetric glaucoma. When applied with stimuli at high temporal frequency, the new paradigm had higher diagnostic sensitivity and specificity than the traditional frequency-doubling test. The findings also support the viewpoint that selective evaluation of magnocellular pathway function could facilitate the earlier detection of functional defects in glaucoma before visual field defects by standard perimetry.

Physical activity restriction in age-related eye disease: a cross-sectional study exploring fear of falling as a potential mediator.

BackgroundFear of falling (FoF) is predictive of decreased physical activity. This study sought to determine if FoF mediates the relationship between decreased vision and physical activity restriction in individuals with glaucoma and age-related macular degeneration (AMD).MethodsAccelerometers were used to measure physical activity over 1 week in 59 control, 83 glaucoma, and 58 AMD subjects. Subjects completed the University of Illinois at Chicago Fear of Falling Questionnaire, and the extent of FoF was estimated using Rasch analysis. In negative binomial models adjusting for demographic, health, and social factors, FoF was investigated as a potential mediator between the severity of visual field (VF) loss (in glaucoma patients) or the severity of contrast sensitivity (CS) loss (in AMD patients) and decreased engagement in physical activity, defined as minutes spent in moderate-to-vigorous physical activity (MVPA) per day.ResultsIn multivariate negative binomial regression models, 5-decibels worse VF mean deviation was associated with 26 % less engagement in MVPA [rate ratio (RR) = 0.74, p < 0.01] amongst glaucoma subjects. When FoF was added to the model, the RR increased from 0.74 to 0.78, and VF loss severity remained associated with less MVPA at a statistically significant level (p < 0.01). Likewise, 0.1 log units worse CS was associated with 11 % less daily MVPA (RR = 0.89, p < 0.01) amongst AMD subjects. When FoF was added to the model, the RR increased from 0.89 to 1.02, and CS loss was no longer associated with MVPA at a statistically significant level (p = 0.53).ConclusionsFoF may mediate the relationship between vision loss and physical activity restriction amongst patients with AMD. Future work should determine optimal strategies for reducing FoF in individuals with vision loss in order to prevent the deleterious effects of physical activity restriction.Electronic supplementary materialThe online version of this article (doi:10.1186/s12877-015-0062-8) contains supplementary material, which is available to authorized users.

The effects of simulated vision impairments on the cone of gaze.

Detecting the gaze direction of others is critical for many social interactions. We explored factors that may make the perception of mutual gaze more difficult, including the degradation of the stimulus and simulated vision impairment. To what extent do these factors affect the complex assessment of mutual gaze? Using an interactive virtual head whose eye direction could be manipulated by the subject, we conducted two experiments to assess the effects of simulated vision impairments on mutual gaze. Healthy subjects had to demarcate the center and the edges of the cone of gaze-that is, the range of gaze directions that are accepted for mutual gaze. When vision was impaired by adding a semitransparent white contrast reduction mask to the display (Exp. 1), judgments became more variable and more influenced by the head direction (indicative of a compensation strategy). When refractive blur was added (Exp. 1), the gaze cone shrank from 12.9° (no blur) to 11.3° (3-diopter lens), which cannot be explained by a low-level process but might reflect a tightening of the criterion for mutual gaze as a response to the increased uncertainty. However, the overall effects of the impairments were relatively modest. Elderly subjects (Exp. 2) produced more variability but did not differ qualitatively from the younger subjects. In the face of artificial vision impairments, compensation mechanisms and criterion changes allow us to perform better in mutual gaze perception than would be predicted by a simple extrapolation from the losses in basic visual acuity and contrast sensitivity.

A retrospective of studies on toxic induced loss of color vision and contrast sensitivity: What have we learned?

A retrospective of studies on toxic induced loss of color vision and contrast sensitivity: What have we learned?

Nature of the Visual Loss in Observers With Leber's Congenital Amaurosis Caused by Specific Mutations in RPE65

To characterize visual losses associated with genetic mutations in the RPE65 gene that cause defects in the RPE-specific isomerase, RPE65. RPE65 is an important component of the retinoid cycle that restores 11-cis-retinal after its photoisomerization to its all-trans form. The defects investigated here cause Leber's congenital amaurosis (LCA2), an autosomal, recessively-inherited, severe, congenital-onset rod-cone dystrophy. Vision was assessed in nine patients and 10 normal controls by measuring: (1) long-wavelength sensitive (L-) cone temporal acuity (critical flicker fusion frequency or cff) as a function of target illuminance, and (2) L-cone temporal contrast sensitivity as a function of temporal frequency at a fixed-target illuminance. Measurements were made by modulating either a 650-nm light superimposed on a 480-nm background or the red phosphor of a color monitor on a background produced by the monitor's blue phosphor. RPE65-mutant observers have severely reduced cffs with shallower cff versus log illuminance functions that rise with a mean slope of 4.53 Hz per decade of illuminance compared with 8.69 Hz in normal controls. Consistent with the cff differences, RPE65-mutant observers show losses in temporal contrast sensitivity that increase rapidly with temporal frequency. All RPE65-mutant observers have consistent and substantial losses in temporal acuity and sensitivity compared with normal observers. The losses can be characterized by the addition of two sluggish filters within the mutant visual pathway, both filters with a time constant of 29.5 ms (i.e., low-pass filters with cut-off frequencies of 5.40 Hz).

Presbyopia-correcting intraocular lenses and corneal refractive procedures: a review for retinal surgeons.

To review the specific challenges and pitfalls that vitreoretinal surgeons may face when operating on eyes with presbyopia-correcting intraocular lenses or previous corneal refractive surgery. In addition, this review aims to familiarize vitreoretinal surgeons with specifications of currently available Food and Drug Administration-approved presbyopia-correcting intraocular lenses. Review of current literature performed with PubMed for search terms "presbyopia," "correction," "IOL," "vitreoretinal," "challenges," and "surgical" both singly and in combination as well as closely related terms. Specific intraoperative issues with presbyopia-correcting intraocular lenses that may be encountered include peripheral visualization, condensation, lens material issues particularly with silicone oil, decentration, Z-syndrome, and foveal image displacement. Every patient undergoing retinal surgery should also be asked about previous laser-assisted in situ keratomileusis/photorefractive keratectomy because those eyes require special attention to surface hydration and care to avoid epithelial removal if possible. Intracorneal ring segments and corneal inlays can cause effects similar to those of a small pupil. However, these can be managed with thorough preoperative evaluation and various intraoperative maneuvers. In addition, retinal physicians should be aware that macular disorders, such as age-related macular degeneration, may be exacerbated by potential loss of contrast sensitivity.

Mechanism underlying spatial vision deficit of monocular amblyopia based on the theory of Magnocellular and Parvocellular (M-P) pathways

To investigate the relationship between the characteristics of spatial vision deficit and the degree of amblyopia in monocular amblyopes, and to analyze its mechanism with the theory of Magnocellular and Parvocellular pathways. One hundred and eleven patients with monocular amblyopes aged 7-34 were included in this study. Distance best corrected visual acuity (BCVA) in logMAR units and contrast sensitivity function test were performed on both eyes in all patients with ETDRS digital visual chart and functional test system OPTECR 6500. The spatial vision of amblyopic and non-amblyopic eyes was evaluated by the AULCSF, Smax, Frmax and cutSF derived from the curve of contrast sensitivity function. The degree of amblyopia was significantly correlated with the difference of AULCSF between the amblyopic and non-amblyopia eyes (r=-0.83, P<0.01). BCVA of amblyopic eyes was significantly correlated with AULCSF, CutSF, Smax, Frmax(r=-0.68, -0.80, -0.73, -0.56, respectively; P<0.01). In amblyopic eyes, significant difference in BCVA, AULCSF, Smax, Frmax and CutSF was seen among different amblyopic groups (P<0.01), which was defined by the degree of amblyopia. In non-amblyopic eyes,no significant difference in BCVA, AULCSF, Smax, Frmax and CutSF was noted among different amblyopic groups (P>0.05). In mild amblyopes, no significant difference in AULCSF and Frmax was found between the amblyopic eyes and non-amblyopic eyes (P>0.05), while Smax and CutSF were significantly different. However, in moderate and severe amblyopes, significant differences in BCVA, AULCSF, Smax, Frmax and CutSF was seen between the amblyopic and non-amblyopic eyes (P<0.01). In amblyopic eyes, significant difference in contrast sensitivity was noted in all kinds of spatial frequencies among different amblyopic groups (P<0.01), and in non-amblyopic eyes, significant differences in contrast sensitivity was not seen in all kinds of spatial frequencies among different amblyopic groups. The AULCSF, CutSF, Smax and Frmax are accorded with visual acuity for evaluation of the spatial vision of amblyopia. As the severity of amblyopia increases, the overall function of spatial vision in amblyopic eyes gradually decreases, the resolution ability of high spatial frequency is gradually weaken, the peak of contrast detection function gradually descends, and the optimal spatial frequency for contrast detection offsets toward low level of spatial frequency. Mild monocular amblyopia produces spatial contrast sensitivity loss in high spatial vision, suggesting there may be decreased sensitivity of the Parvocellular pathway, and no significant anomalous processing of Magnocellular Pathway. Whereas, in moderate and severe amblyopes, a generalized loss of sensitivity is observed at each spatial frequency. This result shows that both Magnocellular and Parvocellular pathways are damaged in different degrees, especially in Parvocellular pathway.

Influence of multiple sclerosis, age and degree of disability, in the position of the contrast sensitivity curve peak

Context:Contrast sensitivity (CS) function is one of the most important tests available for evaluating visual impairment. Multiple sclerosis (MS) can produce highly selective losses in visual function and psychophysical studies have demonstrated CS deficits for some spatial frequencies.Aims:This work studies the differences in CS between a group of controls and a group of MS patients, focusing on the location of the maximum sensitivity peak, shape of the curve, and determination of the most affected spatial frequencies.Materials and Methods:Using a sinusoidal stimulus the authors assessed CS function in 28 subjects with definitive relapsing remitting MS, and in 50 controls with acuities of 20/25 or better. The peaks of the CS curves were studied by fitting third degree polynomials to individual sets of data.Results:Compared with the control group, the CS function curve for MS subjects showed more deficits in extreme points (low- and high-spatial frequencies). Our results display significant CS losses, at the high-frequencies band level, in the beginning of the disease. When the disease progresses and the disabilities appear, there are greater losses at the low-frequencies band level. In average, the CS curve peaks for the MS group were shifted in relation to the control group.Conclusions:CS losses in the MS group suggest an association with ageing and disability level in the expanded disability status scale. The position of the CS function peak is influenced by MS, age, and degree of disability.