Visual evoked potentials in patients with congenital color vision deficiency.

BACKGROUND/AIM: Congenital color vision deficiency (CCVD) is an eye disease characterized by abnormalities in the cone cells in the photoreceptor layer. Visual evoked potentials (VEPs) are electrophysiological tests that physiologically examine the optic nerve, other visual pathways, and the visual cortex. The aim of this research was to determine whether there are VEP abnormalities in CCVD patients. METHODS: Patients with CCVD and healthy individuals were included in this prospective case-control study. Participants with eye disease or neurodegenerative disease were excluded from the study. Pattern reversal VEP (PVEP), flash VEP (FVEP), and optical coherence tomography were performed on all participants. RESULTS: Twenty healthy individuals (15 male) and 21 patients with CCVD (18 male) were included in the study. The mean ages of healthy individuals and patients with CCVD were 29.8 ± 9.6 and 31.1 ± 10.9 years (p = 0.804). Retinal nerve fiber layer thickness and central macular thickness values did not differ between the two groups. In PVEP, Right P100, Left N75, P100, N135 values were delayed in CCVD patients compared to healthy individuals (p = 0.001, p = 0.032, p = 0.003, p = 0.032). At least one PVEP and FVEP abnormality was present in nine (42.9%) and six (28.6%) of the patients, respectively. PVEP or FVEP abnormalities were found in 13 (61.9%) of the patients. CONCLUSION: This study indicated that there may be PVEP and FVEP abnormalities in patients with CCVD.

Chromatic vision and structural assessment in primary congenital glaucoma.

Primary congenital glaucoma is a rare disease that occurs in early birth and can lead to low vision. Evaluating affected children is challenging and there is a lack of studies regarding color vision in pediatric glaucoma patients. This cross-sectional study included 21 eyes of 13 children with primary congenital glaucoma who were assessed using the Farnsworth D-15 test to evaluate color vision discrimination and by spectral domain optical coherence tomography to measure retinal fiber layer thickness. Age, visual acuity, cup-to-disc ratio and spherical equivalent data were also collected. Global and sectional circumpapillary and macular retinal fiber layer thicknesses were measured and compared based on color vision test performance. Four eyes (19%) failed the color vision test with diffuse dyschromatopsia patterns. Only age showed statistical significance in color vision test performance. Global and sectional circumpapillary and macular retinal fiber layer thicknesses were similar between the color test outcomes dyschromatopsia and normal. While the color vision test could play a role in assessing children with primary congenital glaucoma, further studies are needed to correlate it with damage to retinal fiber layer thickness.

Comparison of Two Printed Pseudoisochromatic Tests for Color Vision Assessment.

SIGNIFICANCE: The Waggoner PIP24 is a pseudoisochromatic test with a pattern similar to the Ishihara test. This study determined that the W-PIP24 can be used clinically to yield screening results (or sensitivity and specificity) comparable with the Ishihara. PURPOSE: This study aimed to determine whether the W-PIP24 is equivalent to the Ishihara 38 edition pseudoisochromatic test in detecting red-green color vision defects. Also, the performance of each plate of the W-PIP24 in detecting the color vision defects relative to the Ishihara test was determined. METHODS: Sixty-three individuals with congenital red-green color vision defects and 57 with normal trichromacy were recruited. Participants were tested with both the Ishihara and W-PIP24. The first-order agreement coefficients were calculated for the Ishihara and W-PIP24. The results were also analyzed using specificity, sensitivity, efficiency, and predictive pass and fail values. RESULTS: The agreement between the W-PIP24 and Ishihara test using the recommended criterion of using all plates was perfect. The sensitivity, specificity, predictive pass, and predictive fail were 1.00 (95% confidence interval, 0.94 to 1.00). CONCLUSIONS: This study showed that the W-PIP24 using a failure criterion of three or more errors on screening plates 1 to 15 is equivalent to the Ishihara test while screening for red-green color vision deficiency using a failure criterion of three or more errors on screening plates 1 to 17 of the Ishihara 38 edition.

Structural changes to primary visual cortex in the congenital absence of cone input in achromatopsia.

Autosomal recessive Achromatopsia (ACHM) is a rare inherited disorder associated with dysfunctional cone photoreceptors resulting in a congenital absence of cone input to visual cortex. This might lead to distinct changes in cortical architecture with a negative impact on the success of gene augmentation therapies. To investigate the status of the visual cortex in these patients, we performed a multi-centre study focusing on the cortical structure of regions that normally receive predominantly cone input. Using high-resolution T1-weighted MRI scans and surface-based morphometry, we compared cortical thickness, surface area and grey matter volume in foveal, parafoveal and paracentral representations of primary visual cortex in 15 individuals with ACHM and 42 normally sighted, healthy controls (HC). In ACHM, surface area was reduced in all tested representations, while thickening of the cortex was found highly localized to the most central representation. These results were comparable to more widespread changes in brain structure reported in congenitally blind individuals, suggesting similar developmental processes, i.e., irrespective of the underlying cause and extent of vision loss. The cortical differences we report here could limit the success of treatment of ACHM in adulthood. Interventions earlier in life when cortical structure is not different from normal would likely offer better visual outcomes for those with ACHM.

Cortical Visual Mapping following Ocular Gene Augmentation Therapy for Achromatopsia.

The ability of the adult human brain to develop function following correction of congenital deafferentation is controversial. Specifically, cases of recovery from congenital visual deficits are rare. CNGA3-achromatopsia is a congenital hereditary disease caused by cone-photoreceptor dysfunction, leading to impaired acuity, photoaversion, and complete color blindness. Essentially, these patients have rod-driven vision only, seeing the world in blurry shades of gray. We use the uniqueness of this rare disease, in which the cone-photoreceptors and afferent fibers are preserved but do not function, as a model to study cortical visual plasticity. We had the opportunity to study two CNGA3-achromatopsia adults (one female) before and after ocular gene augmentation therapy. Alongside behavioral visual tests, we used novel fMRI-based measurements to assess participants' early visual population receptive-field sizes and color regions. Behaviorally, minor improvements were observed, including reduction in photoaversion, marginal improvement in acuity, and a new ability to detect red color. No improvement was observed in color arrangement tests. Cortically, pretreatment, patients' population-receptive field sizes of early visual areas were untypically large, but were decreased following treatment specifically in the treated eye. We suggest that this demonstrates cortical ability to encode new input, even at adulthood. On the other hand, no activation of color-specific cortical regions was demonstrated in these patients either before or up to 1 year post-treatment. The source of this deficiency might be attributed either to insufficient recovery of cone function at the retinal level or to challenges that the adult cortex faces when computing new cone-derived input to achieve color perception.SIGNIFICANCE STATEMENT The possibility that the adult human brain may regain or develop function following correction of congenital deafferentation has fired the imagination of scientists over the years. In the visual domain, cases of recovery from congenital deficits are rare. Gene therapy visual restoration for congenital CNGA3-achromatopsia, a disease caused by cone photoreceptor dysfunction, gave us the opportunity to examine cortical function, to the best of our knowledge for the first time, both before and after restorative treatment. While behaviorally only minor improvements were observed post-treatment, fMRI analysis, including size algorithms of population-receptive fields, revealed cortical changes, specifically receptive field size decrease in the treated eyes. This suggests that, at least to some degree, the adult cortex is able to encode new input.

Color Vision Deficiency Among Doctors: Can We Make Useful Adaptations to the Color Codes Used in the Clinical Environment?

ABSTRACT: Color vision deficiency (formerly known as color blindness) is common as a congenital and as an acquired condition. Some professions, most famously commercial aviation, require their members to demonstrate normal color vision. In the United States and United Kingdom, no restriction is placed on the ability of the color-deficient doctor to practice medicine, although there is evidence that certain clinical discriminations are harder for such doctors. Generally ignored has been the difficulty and the potential for error that arises from the use of color codes in clinical equipment. In this review, we introduce the basic concepts of color deficiency, summarize evidence for the challenges it poses to the doctor, examine global variation in policy, show the potential for confusion among clinical color codes, and suggest how the current situation could be improved to enhance both patient safety and the well-being of the color-deficient doctor.

Case Report: Effect of Haploscopic Filter on Contrast Sensitivity Function and Color Vision Tests.

SIGNIFICANCE: The options that can help patients with congenital color vision defect, to a better professional and leisure adaptation, are very limited. Different haploscopic lenses can be considered, and their effects need to be investigated in patients with different defects. PURPOSE: The purpose of this study was to present and discuss the effect of a pair of asymmetric long-pass filters fitted for deuteranopia, with the result of a 60% improvement in distinguishing red-green plates when compared with baseline. CASE REPORT: We report the case of a 51-year-old man with congenital deuteranopia fitted with haploscopic ChromaGen filters. During the 2-month follow-up, we observed a decrease in left-eye logMAR visual acuity and contrast sensitivity with an increased ability to discriminate the plates of different color vision tests (Ishihara, Farnsworth, and Hardy-Rand-Rittler). The visual outcomes are discussed considering the spectral sensitivity curves of each filter, measured with a spectrophotometric device. CONCLUSIONS: This report describes an improvement in the ability to resolve color vision plates after using asymmetric haploscopic filters showing a left-eye decrease in logMAR visual acuity and contrast sensitivity function. Subjects with a history of color vision deficiency might benefit from using haploscopic filters that selectively minimize the transmittance within a specific bandwidth to improve the color discrimination in deutan color vision deficiency. The simultaneous analysis of the color vision outcomes and transmittance spectrum of the haploscopic filters might contribute to a better understanding of the mechanisms behind the claimed efficacy of these devices.

Preservation of the Foveal Avascular Zone in Achromatopsia Despite the Absence of a Fully Formed Pit.

Purpose: To examine the foveal avascular zone (FAZ) in patients with congenital achromatopsia (ACHM). Methods: Forty-two patients with genetically confirmed ACHM were imaged either with Optovue's AngioVue system or Zeiss's Plex Elite 9000, and the presence or absence of a FAZ was determined. For images where a FAZ was present and could be confidently segmented, FAZ area, circularity index, and roundness were measured and compared with previously published normative values. Structural optical coherence tomography images were acquired to assess the degree of foveal hypoplasia (number and thickness of inner retinal layers present at the fovea). Results: A FAZ was present in 31 of 42 patients imaged (74%), although no determination could be made for 11 patients due to poor image quality (26%). The mean ± SD FAZ area for the ACHM retina was 0.281 ± 0.112 mm2, which was not significantly different from the previously published normative values (P = 0.94). However, their FAZs had decreased circularity (P < 0.0001) and decreased roundness (P < 0.0001) compared to the normative cohort. In the patients with ACHM examined here, the FAZ area decreased as the number and thickness of the retained inner retinal layers increased. Conclusions: Our data demonstrate that despite the presence of foveal hypoplasia, patients with ACHM can have a FAZ. This is distinct from other conditions associated with foveal hypoplasia, which generally show an absence of the FAZ. In ACHM, FAZ formation does not appear to be sufficient for complete pit formation, contrary to some models of foveal development.

Genotypes and phenotypes of genes associated with achromatopsia: A reference for clinical genetic testing.

Purpose: Achromatopsia is a congenital autosomal recessive cone disorder, and it has been found to be associated with six genes. However, pathogenic variants in these six genes have been identified in patients with various retinal dystrophies with the exception of achromatopsia. Thus, this study aims to investigate the contribution of these genes in hereditary retinal diseases and the potential genotype-phenotype correlations. Methods: Biallelic variants in six achromatopsia-related genes, namely, CNGA3, CNGB3, GNAT2, ATF6, PDE6C, and PDE6H, were analyzed based on data obtained from 7,195 probands with different eye conditions. A systematic genotype-phenotype analysis of these genes was performed based on these data, along with the data reported in the literature. Results: Biallelic potential pathogenic variants (PPVs) in five of the six genes were identified in 119 probands with genetic eye diseases. The variants in CNGA3 were the most common and accounted for 81.5% (97/119). Of the 119 probands, 62.2% (74/119) have cone-rod dystrophy, whereas only 25.2% (30/119) have achromatopsia. No biallelic pathogenic variants in these genes were identified in patients with rod-dominant degeneration. A systematic review of genotypes and phenotypes revealed certain characteristics of each of the six genes, providing clues for the pathogenicity evaluation of the variants of the genes. Conclusions: PPVs in the six genes were identified in various inherited retinal degeneration diseases, most of which are cone-dominant diseases but no rod-dominant diseases based on the data from a cohort of 7,195 probands with different eye conditions. The systematic genotype-phenotype analysis of these genes will be useful in drafting guidelines for the clinical genetic diagnostic application for the investigated genes.

Interocular Symmetry of Foveal Cone Topography in Congenital Achromatopsia.

Purpose: To determine the interocular symmetry of foveal cone topography in achromatopsia (ACHM) using non-confocal split-detection adaptive optics scanning light ophthalmoscopy (AOSLO). Methods: Split-detector AOSLO images of the foveal cone mosaic were acquired from both eyes of 26 subjects (mean age 24.3 years; range 8-44 years, 14 females) with genetically confirmed CNGA3- or CNGB3-associated ACHM. Cones were identified within a manually delineated rod-free zone. Peak cone density (PCD) was determined using an 80 × 80 µm sampling window within the rod-free zone. The mean and standard deviation (SD) of inter-cell distance (ICD) were calculated to derive the coefficient of variation (CV). Cone density difference maps were generated to compare cone topography between eyes. Results: PCD (mean ± SD) was 17,530 ± 9,614 cones/mm2 and 17,638 ± 9,753 cones/mm2 for right and left eyes, respectively (p = .677, Wilcoxon test). The mean (± SD) for ICD was 9.05 ± 2.55 µm and 9.24 ± 2.55 µm for right and left eyes, respectively (p = .410, paired t-test). The mean (± SD) for CV of ICD was 0.16 ± 0.03 µm and 0.16 ± 0.04 µm for right and left eyes, respectively (p = .562, paired t-test). Cone density maps demonstrated that cone topography of the ACHM fovea is non-uniform with local variations in cone density between eyes. Conclusions: These results demonstrate the interocular symmetry of the foveal cone mosaic (both density and packing) in ACHM. As cone topography can differ between eyes of a subject, PCD does not completely describe the foveal cone mosaic in ACHM. Nonetheless, these findings are of value in longitudinal monitoring of patients during treatment trials and further suggest that both eyes of a given subject may have similar therapeutic potential and non-study eye can be used as a control.

Review of the main colour vision clinical assessment tests. / Revisión de los principales test clínicos para evaluar la visión del color.

INTRODUCTION: Congenital colour vision deficiencies affect 8% of the male and 0.5% of the female population. The study of colour vision is a complex process due to several factors: the psychophysics of vision itself, the difficulty to establish mathematical models for its analysis, the vague correlation of results between different tests, and the influence of external factors such as lighting, the tests condition, or the experience of the examiner and the patient. In the present document, a simplified review was carried out on the main colour vision tests available in clinical practice. MATERIAL AND METHODS: Once a filtered preliminary review was made of the bibliography related to the study of colour vision using the PubMed search tool, the most used tests in clinical practice were selected according to their frequency of use and the purpose for which they were applied. A bibliographic study was then carried out on each particular test according to the design of the shown stimuli, its target population, and its sensitivity and specificity. RESULTS: From the 95 publications found using the PubMed search tool, in 41 of them, colour tests were used by researchers in their methodology. From the 64 colour tests used, 19 of them were different (with 4 of them being different tests adapted by research groups, and 2 of them carried out online). The most used tests were the following: Ishihara test (10.88%), Farnsworth-Munsell (7.04%), Farnsworth-Munsell 100 Hue (6.4%), Cambridge Colour Test (3.84%), Hardy-Rand-Rittler (3.2%), tests developed by the groups (2.56%), the Anomaloscope (1.28%), the online tests (1.28%) and, finally, Colour Assessment and Diagnosis (0.64%), Pflüger Trident Colour Plates (0.64%), Toothguide Training Box (0.64%), Lanthony Desaturated D-15 (0.64%), City University Test (0.64%), Universal Colour Discrimination Test (0.64%), and Rabin Cone Contrast Test (0.64%). CONCLUSIONS: The Anomaloscope is the "gold standard" in terms of colour vision testing, despite its incompatibility with daily clinical practice. It is fairly complex to use, difficult to understand for children, and its practice requires having the time available. Nevertheless, it is possible to reach an accurate approximation through the combination of some of the tests listed in this article. The above mentioned tests are a good alternative to determine the presence of dyschromatopsia in settings closer to daily clinical practice or in less controlled settings than a clinical study. The major drawback among the wide range of tests available for the study of colour vision is the difficulty to compare results between tests, since units of the reported data are usually different, and experience is required for its correct interpretation. Currently, there is no consensus on which colour test is the most complete. It is, therefore, advisable to use at least 2 tests in order to ensure diagnoses, and have more extensive information about the visual perception of patients.

Behavioural and emotional issues among primary school pupils with congenital colour vision deficiency in the Federal Territory of Kuala Lumpur, Malaysia: A case-control study.

Background: Congenital colour vision deficiency (CCVD) is an untreatable disorder which has lifelong consequences. Increasing use of colours in schools has raised concern for pupils with CCVD. This case-control study was conducted to compare behavioural and emotional issues among age, gender and class-matched pupils with CCVD and normal colour vision (NCV). Methods: A total of 1732 pupils from 10 primary schools in the Federal Territory of Kuala Lumpur were screened, of which 46 pupils (45 males and 1 female) had CCVD. Mothers of male pupils with CCVD (n=44) and NCV (n=44) who gave consent were recruited to complete a self-administered parent report form, Child Behaviour Checklist for Ages 4-18 (CBCL/ 4-18) used to access behavioural and emotional problems. The CBCL/ 4-18 has three broad groupings: Internalising, Externalising and Total Behaviour Problems. Internalising Problems combines the Withdrawn, Somatic Complaints and Anxiety/ Depression sub constructs, while Externalising Problems combines the Delinquent and Aggressive Behaviour sub constructs. Results: Results from CBCL/ 4-18 showed that all pupils from both groups had scores within the normal range for all constructs. However, results from the statistical analysis for comparison, Mann-Whitney U test, showed that pupils with CCVD scored significantly higher for Externalising Problems (U=697.50, p=0.02) and Total Behaviour Problems (U=647.00, p= 0.01). Significantly higher scores were observed in Withdrawn (U=714.00, p=0.02), Thought Problems (U=438.50, p<0.001) and Aggressive Behaviour (U=738.00, p=0.04). Odds ratios, 95% CI, showed significant relative risk for high Total Behaviour Problem (OR:2.39 ,CI:1.0-5.7), Externalising Problems (OR:2.32, CI:1.0-5.5), Withdrawn (OR:2.67, CI:1.1-6.5), Thought Problems (OR:9.64, CI:3.6-26.1) and Aggressive Behaviour (OR:10.26, CI:3.4-31.0) scores among pupils with CCVD. Conclusion: Higher scores among CCVD pupils indicates that they present more behavioural and emotional problems compared to NCV pupils. Therefore, school vision screenings in Malaysia should also include colour vision to assist in the early clinical management of CCVD children.

Psychosocial aspects of colour vision deficiency: Implications for a career in medicine.

Colour vision deficiency (CVD) is a common problem and persons with CVD experience difficulties in daily life, early learning and development, education, choice of careers and work performance. Medical professionals with CVD also report difficulties in everyday tasks, training in medicine and performance of medical duties. However, because of limited evidence, the real impact of CVD on the lives of medical professionals is unclear, especially regarding the practice of medicine by doctors. The nature and severity of CVD, awareness of its impact, personal circumstances and the ability to cope with the deficiency are the major factors that determine the impact of CVD. However, there is a paucity of methodologically sound research on social and psychological aspects of CVD. Currently, early detection, enhancing awareness and offering support are the only proven ways of helping medical professionals with CVD. With the growing emphasis on equality and inclusivity of those with deficiencies, it is desirable to strike a balance between concerns about patient care and the rights of medical professionals with CVD to pursue their careers. Therefore, any future research also needs to focus on psychological aspects of CVD while exploring its impact on a career in medicine.

Dissociations in Coherence Sensitivity Reveal Atypical Development of Cortical Visual Processing in Congenital Achromatopsia.

PURPOSE: While basic visual functions have been described in subjects with congenital achromatopsia (ACHM), little is known about their mid- or high-level cortical visual processing. We compared midlevel cortical visual processing in ACHM subjects (n = 11) and controls (n = 20). METHODS: Abilities to detect global form, global motion, and biological motion embedded in noise were tested across a range of light levels, including scotopic, in which both ACHM subjects and controls must rely on rods. Contrast sensitivity functions (CSFs) were also measured. RESULTS: Achromatopsia subjects showed differential impairments across tests. In scotopic conditions, global form was most impaired, while biological motion was normal. In a subset of three ACHM subjects with normal scotopic CSFs, two of the three showed global form perception worse than controls; all showed global motion comparable to controls; and strikingly, two of the three showed biological motion perception superior to controls. CONCLUSIONS: The cone signal appears to play a crucial role in the development of perception of global form, as in ACHM this is impaired even in scotopic conditions, in which controls also have to rely on rods, and even in ACHM subjects with no scotopic spatial vision loss. In contrast, the rod signal appears sufficient for the development of normal (or even superior) extrastriate biological motion perception. These results suggest that ACHM leads to atypical development of cortical vision, highlighting the need to better understand the potential for further reorganization of cortical visual processing following new therapies aimed at restoring cone function.

Reliability and Repeatability of Cone Density Measurements in Patients with Congenital Achromatopsia.

Adaptive optics scanning light ophthalmoscopy (AOSLO) allows non-invasive assessment of the cone photoreceptor mosaic. Confocal AOSLO imaging of patients with achromatopsia (ACHM) reveals an altered reflectivity of the remaining cone structure, making identification of the cells more challenging than in normal retinas. Recently, a "split-detector" AOSLO imaging method was shown to enable direct visualization of cone inner segments in patients with ACHM. Several studies have demonstrated gene replacement therapy effective in restoring cone function in animal models of ACHM and human trials have on the horizon, making the ability to reliably assess cone structure increasingly important. Here we sought to examine whether absolute estimates of cone density obtained from split-detector and confocal AOSLO images differed from one another and whether the inter- and intra-observer reliability is significantly different between these modes. These findings provide an important foundation for evaluating the role of these images as tools to assess the efficacy of future gene therapy trials.

Color vision deficiency in Zahedan, Iran: lower than expected.

PURPOSE: To estimate the prevalence of congenital red-green color vision defects in the elementary school students of Zahedan in 2012. METHODS: In this cross-sectional study, 1000 students with a mean (±SD) age of 9.0 (±1.4) years were selected randomly from a large primary school population. Color vision was evaluated using the Ishihara pseudoisochromatic color plates (38-plate edition). A daylight fluorescent tube was used as an illuminant C equivalent (i.e., 860 lux, color rendering index greater than 92, and color temperature = 6500 K). Having more than three misreadings on the test was considered a failing criterion. Data were analyzed in SPSS version 17 software using χ2 tests. RESULTS: Nine students (0.9%) made more than three errors on the Ishihara test. Based on this criterion, the prevalence of red-green color vision deficiency in girls and boys was 0.2 and 1.6% (p = 0.02), respectively. CONCLUSIONS: The prevalence of red-green color vision deficiency was found to be significantly lower in Zahedan than comparable reports in the literature.

Is screening for congenital colour vision deficiency in school students worthwhile? A review.

This review analyses the literature on screening for congenital colour vision deficiency in school students, which predominantly uses the Ishihara test. The review was framed with respect to the established Wilson and Jungner criteria for screening programs. These criteria relate to the characteristics of the condition concerned, the performance of the screening test, the existence of treatment options and the performance of screening programs. The literature reviewed suggests that congenital colour vision deficiency has not been shown to increase risk of road traffic crashes and is not a preclusion to driver licensing in most developed countries. The occurrence of congenital colour vision deficiency has been used to limit entry into certain occupations; however, the value of screening school students with regard to occupational preclusion is questionable. Stronger evidence exists indicating no association between congenital colour vision deficiency and level of educational achievement. Studies showing any association between congenital colour vision deficiency and other health and lifestyle impacts were rare. The most commonly used screening test (using Ishihara pseudoisochromatic plates) performs well with respect to detecting red-green colour vision deficiencies. Finally, the only interventions we identified for congenital colour vision deficiency were management ones around the availability of specific tinted lenses and computer programs to aid colour perception in certain tasks. Given this picture, the weight of evidence appears to be in favour of not adopting (or discontinuing) routine colour vision screening programs for school students; however, it may be worthwhile for a career advisor to refer school students to an optometrist or ophthalmologist for colour vision screening, upon expression of interest in an occupation where normal colour vision is either particularly desirable or is a regulatory requirement.

Causes and consequences of inherited cone disorders.

Hereditary cone disorders (CDs) are characterized by defects of the cone photoreceptors or retinal pigment epithelium underlying the macula, and include achromatopsia (ACHM), cone dystrophy (COD), cone-rod dystrophy (CRD), color vision impairment, Stargardt disease (STGD) and other maculopathies. Forty-two genes have been implicated in non-syndromic inherited CDs. Mutations in the 5 genes implicated in ACHM explain ∼93% of the cases. On the contrary, only 21% of CRDs (17 genes) and 25% of CODs (8 genes) have been elucidated. The fact that the large majority of COD and CRD-associated genes are yet to be discovered hints towards the existence of unknown cone-specific or cone-sensitive processes. The ACHM-associated genes encode proteins that fulfill crucial roles in the cone phototransduction cascade, which is the most frequently compromised (10 genes) process in CDs. Another 7 CD-associated proteins are required for transport processes towards or through the connecting cilium. The remaining CD-associated proteins are involved in cell membrane morphogenesis and maintenance, synaptic transduction, and the retinoid cycle. Further novel genes are likely to be identified in the near future by combining large-scale DNA sequencing and transcriptomics technologies. For 31 of 42 CD-associated genes, mammalian models are available, 14 of which have successfully been used for gene augmentation studies. However, gene augmentation for CDs should ideally be developed in large mammalian models with cone-rich areas, which are currently available for only 11 CD genes. Future research will aim to elucidate the remaining causative genes, identify the molecular mechanisms of CD, and develop novel therapies aimed at preventing vision loss in individuals with CD in the future.

[SD-OCT contribution in congenital achromatopsia diagnosis (6 patients)]. / Contribution du SD-OCT de la macula dans le diagnostic de l'achromatopsie congénitale : à propos de 6 patients.

PURPOSE: Achromatopsia (ACH) is a congenital autosomal recessive cone disorder. The puspose is to describe particular SD-OCT macular images in ACH. METHODS: The study included 6 patients from 3 consanguineous Tunisian families with congenital nystagmus and amblyopia with ACH. All patients had clinical examination with fundus photography, autofluorescence, 100-Hue Color vision and the appearance and thickness of all retinal layers were evaluated by spectral-domain optical coherence tomography (SD-OCT). RESULTS: All patients had ACH. The feature was loss of inner- and outer-segments (IS/OS) with disruption of the ciliary layer on OCT and an appearance of partial-thickness hole in the outer macular retina. CONCLUSION: This feature seems to be characteristic of ACH. SD-OCT correlated to clinic signs help the diagnosis.