'The last channel': vision at the temporal margin of the field

The human visual field, on the temporal side, extends to at least 90° from the line of sight. Using a two-alternative forced-choice procedure in which observers are asked to report the direction of motion of a Gabor patch, and taking precautions to exclude unconscious eye movements in the direction of the stimulus, we show that the limiting eccentricity of image-forming vision can be established with precision. There are large, but reliable, individual differences in the limiting eccentricity. The limiting eccentricity exhibits a dependence on log contrast; but it is not reduced when the modulation visible to the rods is attenuated, a result compatible with the histological evidence that the outermost part of the retina exhibits a high density of cones. Our working hypothesis is that only one type of neural channel is present in the far periphery of the retina, a channel that responds to temporally modulated stimuli of low spatial frequency and that is directionally selective.

Early Cone Photoreceptor Outer Segment Length Shortening in RPGR X-Linked Retinitis Pigmentosa

INTRODUCTION

Introduction of retinal gene therapy requires established outcome measures along with thorough understanding of the pathophysiology. Evidence of early, thinned outer segments in RPGR X-linked retinitis pigmentosa could help understand how the level of cone photoreceptor involvement translates to visual potential.

OBJECTIVE

Analysis of foveal photoreceptor outer segment length in a young cohort of RPGR patients to help clarify the reason for absent maximal visual acuity seen.

METHODS

Case-control study of RPGR patients. Quantitative measurement of photoreceptor outer segment by OCT.

RESULTS

Eighteen male RPGR patients and 30 normal subjects were included. Outer segment thickness differed significantly between the RPGR and normal eyes (p < 0.0005). Mean outer segment values were 35.6 ± 2.3 µm and 35.4 ± 2.6 µm for RPGR right and left eyes, respectively. In normal eyes, the mean outer segment thickness was 61.4 ± 0.7 µm for right eyes and 62.4 ± 0.7 µm for left eyes.

CONCLUSIONS

Patients with RPGR X-linked retinitis pigmentosa show thinning of the foveal photoreceptor outer segment thickness early in the disease course, which could be an explanation for the lower maximum visual acuity seen. These findings must be taken into consideration when assessing efficacy outcome measures in retinal gene therapy trials.

[Retinitis pigmentosa]

Retinitis pigmentosa is the most frequent hereditary dystrophy of the retina, with a global prevalence of 1/4.000. The underlying mechanism involves progressive loss, first of the rod photoreceptor cells, followed by the cone photoreceptor cells. Finally, complete blindness may occur. Genetic transmission is known but most cases are sporadic. Few effective treatments exist nowadays and hence regular follow-up is required in a revalidation center.

Blinded by the light: a nonhuman primate model of achromatopsia

Achromatopsia is an inherited retinal degeneration characterized by the loss of cone photoreceptor function. In this issue of the JCI, Moshiri et al. characterize a naturally occurring model of the disease in the rhesus macaque caused by homozygous mutations in the phototransduction enzyme PDE6C. Using retinal imaging, and electrophysiologic and biochemical methods, the authors report a clinical phenotype nearly identical to the human condition. These findings represent the first genetic nonhuman primate model of an inherited retinal disease, and provide an ideal testing ground for the development of novel gene replacement, gene editing, and cell replacement therapies for cone dystrophies.

A CEP290 C-Terminal Domain Complements the Mutant CEP290 of Rd16 Mice In Trans and Rescues Retinal Degeneration

Mutations in CEP290 cause ciliogenesis defects, leading to diverse clinical phenotypes, including Leber congenital amaurosis (LCA). Gene therapy for CEP290-associated diseases is hindered by the 7.4 kb CEP290 coding sequence, which is difficult to deliver in vivo. The multi-domain structure of the CEP290 protein suggests that a specific CEP290 domain may complement disease phenotypes. Thus, we constructed AAV vectors with overlapping CEP290 regions and evaluated their impact on photoreceptor degeneration in Cep290rd16/rd16 and Cep290rd16/rd16;Nrl-/- mice, two models of CEP290-LCA. One CEP290 fragment (the C-terminal 989 residues, including the domain deleted in mutant mice) reconstituted CEP290 function and resulted in cone preservation and delayed rod death. The CEP290 C-terminal domain also improved cilia phenotypes in mouse embryonic fibroblasts and iPSC-derived retinal organoids carrying the Cep290rd16 mutation. Our study strongly argues for in trans complementation of CEP290 mutations by a cognate fragment and suggests therapeutic avenues.

Cone and melanopsin contributions to human brightness estimation: comment

A recent study of large-field subjective brightness perception under different narrowband spectra and different luminances revealed distinct contributions of cone photoreceptors and intrinsically photosensitive retinal ganglion cells containing the photopigment melanopsin. The data from this study were analyzed with a recently published model of spectral sensitivity for full-field brightness incorporating three primary channels: a luminance (achromatic) channel, a blue-yellow opponent color channel, and a melanopsin channel. There was good agreement between predictions based on this model and the recently published brightness perception data.

Isolation of photoreceptors from mature, developing, and regenerated zebrafish retinas, and of microglia/macrophages from regenerating zebrafish retinas

This paper describes experimental procedures for the dissociation of retinal cells of the zebrafish (Danio rerio) for subsequent fluorescence-activated cell sorting (FACS) and gene expression studies. Methods for dissociation of zebrafish retinas followed by FACS and RNA isolation were optimized. This methodology was applied to isolate pure sorted samples of rods, long wavelength-sensitive (LWS) cones, medium wavelength-sensitive (MWS; RH2-2) cones, short wavelength-sensitive (SWS2) cones, and UV-sensitive (SWS1) cones from retinas obtained at selective life-history stages of the zebrafish, and for some of these photoreceptors, following retinal regeneration. We also successfully separated lws1-expressing and lws2-expressing LWS cones from fish of a transgenic line in which lws1 is reported with green fluorescence protein (GFP) and lws2 is reported with red fluorescence protein (RFP). Microglia/macrophages were successfully sorted from regenerating retinas (7 days after a cytotoxic lesion) of a transgenic line in which these immune cells express GFP. Electropherograms verified downstream isolation of high-quality RNA from sorted samples. Examples of post-sorting analysis, as well as results of qRT-PCR studies, validated the purity of sorted populations. For example, qRT-PCR samples derived from isolated Rh2-2 cones contained detectable rh2-2 (opn1mw2) opsin transcripts, but lws opsin transcripts (lws1/opn1lw1, lws2/opn1lw2) were not detected, suggesting that the procedure likely separated double cone pairs. Through this method, pure, sorted cell samples can provide RNA that is reliable for downstream gene expression analyses, such as qRT-PCR and RNA-seq, which may reveal molecular signatures of photoreceptors and microglia for comparative transcriptomics studies.

Genotype determination of the OPN1LW/OPN1MW genes: novel disease-causing mechanisms in Japanese patients with blue cone monochromacy

Blue cone monochromacy (BCM) is characterized by loss of function of both OPN1LW (the first) and OPN1MW (the downstream) genes on the X chromosome. The purpose of this study was to investigate the first and downstream genes in the OPN1LW/OPN1MW array in four unrelated Japanese males with BCM. In Case 1, only one gene was present. Abnormalities were found in the promoter, which had a mixed unique profile of first and downstream gene promoters and a -71A > C substitution. As the promoter was active in the reporter assay, the cause of BCM remains unclear. In Case 2, the same novel mutation, M273K, was present in exon 5 of both genes in a two-gene array. The mutant pigments showed no absorbance at any of the wavelengths tested, suggesting that the mutation causes pigment dysfunction. Case 3 had a large deletion including the locus control region and entire first gene. Case 4 also had a large deletion involving exons 2-6 of the first gene. As an intact LCR was present upstream and one apparently normal downstream gene was present, BCM in Case 4 was not ascribed solely to the deletion. The deletions in Cases 3 and 4 were considered to have been caused by non-homologous recombination.

Chaos and multi-scroll attractors in RCL-shunted junction coupled Jerk circuit connected by memristor

In this paper, a new four-variable dynamical system is proposed to set chaotic circuit composed of memristor and Josephson junction, and the dependence of chaotic behaviors on nonlinearity is investigated. A magnetic flux-controlled memristor is used to couple with the RCL-shunted junction circuit, and the dynamical behaviors can be modulated by changing the coupling intensity between the memristor and the RCL-shunted junction. Bifurcation diagram and Lyapunov exponent are calculated to confirm the emergence of chaos in the improved dynamical system. The outputs and dynamical behaviors can be controlled by the initial setting and external stimulus as well. As a result, chaos can be suppressed and spiking occurs in the sampled outputs under negative feedback, while applying positive feedback type via memristor can be effective to trigger chaos. Furthermore, it is found that the number of multi-attractors in the Jerk circuit can be modulated when memristor coupling is applied on the circuit. These results indicate that memristor coupling can be effective to control chaotic circuits and it is also useful to reproduce dynamical behaviors for neuronal activities.

Distribution of cone density, spacing and arrangement in adult healthy retinas with adaptive optics flood illumination

The aim of this article is to analyse cone density, spacing and arrangement using an adaptive optics flood illumination retina camera (rtx1^™) on a healthy population. Cone density, cone spacing and packing arrangements were measured on the right retinas of 109 subjects at 2°, 3°, 4°, 5° and 6° of eccentricity along 4 meridians. The effects of eccentricity, meridian, axial length, spherical equivalent, gender and age were evaluated. Cone density decreased on average from 28 884 ± 3 692 cones/mm², at 2° of eccentricity, to 15 843 ± 1 598 cones/mm² at 6°. A strong inter-individual variation, especially at 2°, was observed. No important difference of cone density was observed between the nasal and temporal meridians or between the superior and inferior meridians. However, the horizontal and vertical meridians differed by around 14% (T-test, p<0.0001). Cone density, expressed in units of area, decreased as a function of axial length (r² = 0.60), but remained constant (r² = 0.05) when cone density is expressed in terms of visual angle supporting the hypothesis that the retina is stretched during the elongation of the eyeball. Gender did not modify the cone distribution. Cone density was slightly modified by age but only at 2°. The older group showed a smaller density (7%). Cone spacing increased from 6,49 ± 0,42 μm to 8,72 ± 0,45 μm respectively between 2° and 6° of eccentricity. The mosaic of the retina is mainly triangularly arranged (i.e. cells with 5 to 7 neighbors) from 2° to 6°. Around half of the cells had 6 neighbors.

[Research progress of treatment strategies for retinitis pigmentosa]

Retinitis pigmentosa (RP) is a genetically heterogeneous group of hereditary retinal disorders characterized by photoreceptor cell death, associated with night blindness, vision loss, progressive peripheral visual field loss and abnormalities in the electroretinogram. A number of gene defects have so far been associated with RP, which cause a progressive loss of rod photoreceptor function, followed by cone photoreceptor dysfunction and eventually complete blindness. The rate of blindness related to RP is high. At present there is no effective therapeutic strategy for RP. In recent years, with the progress of molecular biology technique, many new therapeutic approaches have become promising. This article summarizes the pathogenesis of RP and gives a brief overview of related research progress of RP therapeutic strategies. (Chin J Ophthalmol, 2017, 53: 148-153).

Novel mutations in the gene for α-subunit of retinal cone cyclic nucleotide-gated channels in a Japanese patient with congenital achromatopsia

PURPOSE

To present the characteristics and pathology of a patient with congenital achromatopsia.

PATIENT AND METHODS

The patient was a 22-year-old Japanese woman who was 8 years old when she first visited our clinic. Comprehensive ophthalmic examinations including visual acuity measurements, perimetry, optical coherence tomography (OCT), fundus autofluorescence (FAF) imaging, electroretinography (ERG), and color vision tests were performed. Her genomic DNA was used as the template for the amplification of exons of five candidate genes for achromatopsia; CNGA3, CNGB3, GNAT2, PDE6C, and PDE6H, and the amplified products were sequenced. A missense mutation, found in the CNGA3, was studied both electrophysiologically and biochemically.

RESULTS

Her phenotype was typical of congenital complete achromatopsia. She was followed for 14 years, and her vision and fundus findings were stable. However, the scotopic ERG b-waves at age 22 were smaller than those at age 8, and her FAF images showed increased autofluorescence in both maculae. Genetic examinations revealed combined heterozygous mutations of c.997_998delGA and p.M424V in the CNGA3 gene. The homomeric channel consisting of the CNGA3 subunit with the p.M424V mutation had a weak cGMP-activated current in patch-clamp recordings. In heterologous expression analyses, the expression at the cell surface of the mutant CNGA3 subunit was about 28 % of the wild type.

CONCLUSIONS

The two novel mutations found in the CNGA3 gene, c.997_998delGA and p.M424V, can cause complete achromatopsia. The vision of the patient was stationary until the third decade of life although the FAF was altered at the age of 22 years.

[Analysis of Observers Metamerism Differences for Different Retinal Cone Visual Responses]

In order to investigate the cone's spectral responses under different conditions for different aged observers with normal color vision, nine color patches with different hue angles distributed uniformly on the CIELAB color space were prepared, and the 27-35 observers were organized to carry out color matching experiments on a monitor to match the nine printed color samples under four different viewing conditions including two illuminances, and two viewing fields. The spectral data obtained from the color matching experiments were compared with the spectral data of the nine target colors and used to test the performances of eleven color matching functions including CIE1931, CIE1964, CIE2006, Sarkar's S1-S8 in terms of the percentage of the minimum CIEDE2000 value. For the four experiments, CIE2006 and S6 performed the best and with S1, S2 the worst. For different observers, the visual spectral responses' of the retinal cone are different and the age has the obvious influence on the visual spectral responses. The observer metamerism is mainly caused by the different spectral response of the (A) channel and for most observers the differences appeared at the responses of the peak wavelength, and the shift of the peak wavelength has no significant influence on the observers metamerism. The experimental results can provide evidences for the classification of the color matching functions for different observer categories and theoretical basis for the investigation of the observers metamerism.

Viral-mediated RdCVF and RdCVFL expression protects cone and rod photoreceptors in retinal degeneration

Alternative splicing of nucleoredoxin-like 1 (Nxnl1) results in 2 isoforms of the rod-derived cone viability factor. The truncated form (RdCVF) is a thioredoxin-like protein secreted by rods that promotes cone survival, while the full-length isoform (RdCVFL), which contains a thioredoxin fold, is involved in oxidative signaling and protection against hyperoxia. Here, we evaluated the effects of these different isoforms in 2 murine models of rod-cone dystrophy. We used adeno-associated virus (AAV) to express these isoforms in mice and found that both systemic and intravitreal injection of engineered AAV vectors resulted in RdCVF and RdCVFL expression in the eye. Systemic delivery of AAV92YF vectors in neonates resulted in earlier onset of RdCVF and RdCVFL expression compared with that observed with intraocular injection using the same vectors at P14. We also evaluated the efficacy of intravitreal injection using a recently developed photoreceptor-transducing AAV variant (7m8) at P14. Systemic administration of AAV92YF-RdCVF improved cone function and delayed cone loss, while AAV92YF-RdCVFL increased rhodopsin mRNA and reduced oxidative stress by-products. Intravitreal 7m8-RdCVF slowed the rate of cone cell death and increased the amplitude of the photopic electroretinogram. Together, these results indicate different functions for Nxnl1 isoforms in the retina and suggest that RdCVF gene therapy has potential for treating retinal degenerative disease.

Individual variation in cone photoreceptor density in house sparrows: implications for between-individual differences in visual resolution and chromatic contrast

Between-individual variation has been documented in a wide variety of taxa, especially for behavioral characteristics; however, intra-population variation in sensory systems has not received similar attention in wild animals. We measured a key trait of the visual system, the density of retinal cone photoreceptors, in a wild population of house sparrows (Passer domesticus). We tested whether individuals differed from each other in cone densities given within-individual variation across the retina and across eyes. We further tested whether the existing variation could lead to individual differences in two aspects of perception: visual resolution and chromatic contrast. We found consistent between-individual variation in the densities of all five types of avian cones, involved in chromatic and achromatic vision. Using perceptual modeling, we found that this degree of variation translated into significant between-individual differences in visual resolution and the chromatic contrast of a plumage signal that has been associated with mate choice and agonistic interactions. However, there was no evidence for a relationship between individual visual resolution and chromatic contrast. The implication is that some birds may have the sensory potential to perform "better" in certain visual tasks, but not necessarily in both resolution and contrast simultaneously. Overall, our findings (a) highlight the need to consider multiple individuals when characterizing sensory traits of a species, and (b) provide some mechanistic basis for between-individual variation in different behaviors (i.e., animal personalities) and for testing the predictions of several widely accepted hypotheses (e.g., honest signaling).

Clinical features and differential diagnosis of acute idiopathic blind spot enlargement syndrome

PURPOSE

To study the clinical manifestations and the diagnostic and differential diagnostic characteristics of acute idiopathic blind spot enlargement syndrome (AIBSES).

METHODS

Six patients diagnosed with AIBSES underwent complete eye examinations including fundus photography, fundus fluorescein angiography(FFA), indocyanine green angiography (ICGA), optical coherence tomography (OCT), electroretinogram (ERG), and visual field examinations.

RESULTS

All patients had enlarged blind spots of variable sizes and densities. Three eyes had mild swelling of the optic disc and one eye had peripapillary scarring that corresponded to the permanent field defect. Two patients who underwent FFA had fluorescein leakage of blood vessels around the optic disc and ICGA highlighted diffuse, small hypofluorescent spots scattering throughout the posterior pole. OCT showed that the inner and outer segment (IS/OS) line were absent in five patients and the middle cone outer segment tip line was absent in the nasal macular area in one eye.

CONCLUSION

AIBSES is a rare outer retinopathy. Visual field examination and OCT are the most important means of detection. ICGA and FAF can determine the range of lesions earlier, and the progress of the disease should be taken into account when making a diagnosis.

Immuno-histochemical analysis of rod and cone reaction to RPE65 deficiency in the inferior and superior canine retina

Mutations in the RPE65 gene are associated with autosomal recessive early onset severe retinal dystrophy. Morphological and functional studies indicate early and dramatic loss of rod photoreceptors and early loss of S-cone function, while L and M cones remain initially functional. The Swedish Briard dog is a naturally occurring animal model for this disease. Detailed information about rod and cone reaction to RPE65 deficiency in this model with regard to their location within the retina remains limited. The aim of this study was to analyze morphological parameters of cone and rod viability in young adult RPE65 deficient dogs in different parts of the retina in order to shed light on local disparities in this disease. In retinae of affected dogs, sprouting of rod bipolar cell dendrites and horizontal cell processes was dramatically increased in the inferior peripheral part of affected retinae, while central inferior and both superior parts did not display significantly increased sprouting. This observation was correlated with photoreceptor cell layer thickness. Interestingly, while L/M cone opsin expression was uniformly reduced both in the superior and inferior part of the retina, S-cone opsin expression loss was less severe in the inferior part of the retina. In summary, in retinae of young adult RPE65 deficient dogs, the degree of rod bipolar and horizontal cell sprouting as well as of S-cone opsin expression depends on the location. As the human retinal pigment epithelium (RPE) is pigmented similar to the RPE in the inferior part of the canine retina, and the kinetics of photoreceptor degeneration in humans seems to be similar to what has been observed in the inferior peripheral retina in dogs, this area should be studied in future gene therapy experiments in this model.

Retinal spectral domain optical coherence tomography in early atrophic age-related macular degeneration (AMD) and a new metric for objective evaluation of the efficacy of ocular nutrition

Purpose: A challenge in ocular preventive medicine is identification of patients with early pathological retinal damage that might benefit from nutritional intervention. The purpose of this study is to evaluate retinal thinning (RT) in early atrophic age-related macular degeneration (AMD) against visual function data from the Zeaxanthin and Visual Function (ZVF) randomized double masked placebo controlled clinical trial (FDA IND #78973). Methods: Retrospective, observational case series of medical center veterans with minimal visible AMD retinopathy (AREDS Report #18 simplified grading 1.4/4.0 bilateral retinopathy). Foveal and extra-foveal four quadrant SDOCT RT measurements were evaluated in n = 54 clinical and ZVF AMD patients. RT by age was determined and compared to the OptoVue SD OCT normative database. RT by quadrant in a subset of n = 29 ZVF patients was correlated with contrast sensitivity and parafoveal blue cone increment thresholds. Results: Foveal RT in AMD patients and non-AMD patients was preserved with age. Extrafoveal regions, however, showed significant slope differences between AMD patients and non-AMD patients, with the superior and nasal quadrants most vulnerable to retinal thinning (sup quad: −5.5 μm/decade thinning vs. Non-AMD: −1.1 μm/decade, P < 0.02; nasal quad: −5.0 μm/decade thinning vs. Non-AMD: −1.0 μm/decade, P < 0.04). Two measures of extrafoveal visual deterioration were correlated: A significant inverse correlation between % RT and contrast sensitivity (r = −0.33, P = 0.01, 2 Tailed Paired T) and an elevated extrafoveal increment blue cone threshold (r = +0.34, P = 0.01, 2 Tailed T). Additional SD OCT RT data for the non-AMD oldest age group (ages 82–91) is needed to fully substantiate the model. Conclusion: A simple new SD OCT clinical metric called “% extra-foveal RT” correlates well with functional visual loss in early AMD patients having minimal visible retinopathy. This metric can be used to follow the effect of repleting ocular nutrients, such as zinc, antioxidants, carotenoids, n-3 essential fats , resveratrol and vitamin D.

Turning a blind eye to anti-VEGF toxicities

Excessive blood vessel growth is a key feature of many retinal diseases, and recently, anti-VEGF therapy has been successfully applied to treat neovascular age-related macular degeneration (AMD), diabetic macular edema, and retinal vein occlusion. In this issue of the JCI, Kurihara et al. reveal an essential role of Vegfa in maintaining choroid vasculature and cone photoreceptors, critical for central and color vision. Their findings suggest that therapeutic approaches to blocking VEGF signaling in retinal diseases might have unexpected detrimental side effects and that the development of alternative strategies might be necessary.

Blue flash ERG PhNR changes associated with poor long-term glycemic control in adolescents with type 1 diabetes

PURPOSE

To investigate the relationship between long-term glycemic control and photopic negative response (PhNR) changes in the blue flash ERG in adolescents with type 1 diabetes (T1D) without diabetic retinopathy (DR).

METHODS

After light adaptation, ERG responses to 1.60 cd·s/m(2) blue (420 nm) flashes (blue flash ERG) and 3.0 cd·s/m(2) white flashes (LA 3.0 ERG) were recorded in 22 patients (age range, 12 to 19 years) and 28 age-similar control subjects. The primary outcome measure was the amplitude of the PhNR. Secondary outcome measures were the amplitude and implicit time of the a-wave and b-wave. Multiple regression analyses were conducted with glycated hemoglobin (HbA(1c)) values and the time since diagnosis of T1D as covariates.

RESULTS

Blue flash ERG PhNR amplitudes were reduced (P = 0.005) in patients compared with control subjects. Multiple regression analysis demonstrated that a 1-unit increase in HbA(1c) was associated with a 15% decrease in the blue flash ERG PhNR amplitude (r = 0.61, P = 0.003). Compared with controls blue flash ERG a-waves (P = 0.03) and b-waves (P = 0.02) were delayed in patients but were not significantly associated with HbA(1c) or time since diagnosis of T1D. None of the ERG measures in the LA 3.0 ERG were significantly different in patients compared with controls.

CONCLUSIONS

Poorer long-term glycemic control is associated with worsening inner retinal dysfunction involving short-wavelength cone pathways of adolescents with T1D and no clinically visible DR. Future studies are warranted to determine whether changes in the blue flash ERG PhNR are a predictive marker of subclinical DR.

A novel recessive GUCY2D mutation causing cone-rod dystrophy and not Leber's congenital amaurosis

Cone-rod dystrophies are inherited retinal dystrophies that are characterized by progressive degeneration of cones and rods, causing an early decrease in central visual acuity and colour vision defects, followed by loss of peripheral vision in adolescence or early adult life. Both genetic and clinical heterogeneity are well known. In a family with autosomal recessive cone-rod dystrophy, genetic analyses comprising genome scan with microsatellite markers, fine mapping and candidate gene approach resulted in the identification of a homozygous missense GUCY2D mutation. This is the first GUCY2D mutation associated with autosomal recessive cone-rod dystrophy rather than Leber's congenital amaurosis (LCA), a severe disease leading to childhood blindness. This study hence establishes GUCY2D, which is a common cause for both recessive LCA and dominant cone-rod dystrophy, as a good candidate for autosomal recessive cone-rod dystrophy.

Efficacy of topical dorzolamide for treatment of cystic macular lesions in a patient with enhanced S-cone syndrome

The purpose of this study was to evaluate the efficacy of topical dorzolamide 2% eye drops on macular function and thickness in a case of enhanced S-cone syndrome (ESCS). A 24-year-old Asian man with enhanced S-cone syndrome treated with topical dorzolamide in the left eye participated in the study. Examinations performed before and during treatment were included visual acuity (VA), contrast sensitivity measured with briefly presented grating targets (grating CS) and the Pelli-Robson chart (P-R CS), microperimetry (MP), and spectral-domain optical coherence tomography (SD-OCT). Following 4 months of treatment, the mean thickness of the central 1-mm foveal subfield of the left eye, as measured by SD-OCT, decreased from 551 to 242 μm. Mean MP sensitivity within the central 12 degrees (28 points) increased from 9.4 dB at baseline to 11.2 dB. Although Pelli-Robson contrast sensitivity improved only minimally in the left eye, grating contrast sensitivity improved by more than a factor of two. Mean log MAR VA was 0.22 OD and 1.00 OS (at baseline), which improved to 0.10 OD and 0.66 OS after 4 months of treatment. The results indicate that in our patient with enhanced S-cone syndrome, treatment with topical dorzolamide was effective in improving macular thickness, VA, microperimetry sensitivity, and grating contrast sensitivity. These measures of retinal structure and function are sensitive tools for evaluating the effects of treatment in enhanced S-cone syndrome patients with cystoid macular edema. Further investigation is warranted to assess the relationships among visual performance for daily activities, visual sensitivity, and macular thickness.

[Case of unilateral impairment of short-wavelength sensitive cone with sudden onset]

BACKGROUND

Compare to either the middle or the long cones, short cones (S-cone) are easily damaged.

CASE

A 62 year-old men complained of acute tritan OS. The corrected visual acuity was 1.2 OU. Routine ocular examinations showed no remarkable abnormalities, but we detected impaired responses using S-cone ERG and blue-on-yellow perimetry OS. We diagnosed this case as acute damage of the blue cone.

CONCLUSION

S-cone damage can be determined by electro-physiological and psychophysical examinations in cases of unilateral color abnormality.