Loss Of Color Discrimination Research Articles

Potential value of color vision aids for varying degrees of color vision deficiency.

Red-green color vision deficiency (CVD) is the most common single locus genetic disorder in humans, affecting approximately 8% of males and 0.4% of females [G. H. M. Waaler, Acta Ophthalmol.5, 309 (2009)10.1111/j.1755-3768.1927.tb01016.x]; however, only about 1/4 of CVD individuals are dichromats who rely on only two cone types for color vision. The remaining 3/4 are anomalous trichromats whose CVD is milder, being based on three cone types, and who still perform remarkably well on many color-based tasks. To illustrate this, we have developed an algorithm that computes the relative loss of color discrimination in red-green CVD individuals with varying degrees of deficiency and accurately simulates their color experience for color normal observers. The resulting simulation illustrates the large gap in color discrimination between dichromats and even the most severe anomalous trichromats, showing that, relative to dichromats, the majority of anomalous trichromats can function without aids for color vision deficiency.

PRO58 Beyond Color Blindness: The Patient and Societal IMPACT of Photoaversion and Vision Loss Associated with Achromatopsia

This review aimed to identify the burden of achromatopsia, a rare inherited retinal condition associated with loss of cone function and consequent visual impairment. Literature databases (MEDLINE, Embase, and Cochrane Reviews) were searched for articles describing the clinical, humanistic, or economic burden of achromatopsia in the US, Japan, France, Germany, Italy, Spain, and the UK, published in English between 2014 and 2019. This was supplemented by web searches of clinical and patient organizations and a review of references from identified articles. The literature search identified 2 qualitative studies of humanistic burden and 12 studies of clinical burden. The estimated incidence of achromatopsia is approximately 1:30,000 worldwide. A survey of affected families reported frequent diagnostic delays and misdiagnosis. Achromatopsia is characterized by reduced visual acuity, nystagmus, debilitating photoaversion, and loss of color discrimination. A survey of people with achromatopsia found that reduced visual acuity and photoaversion were the symptoms patients would most like to improve, implying the greatest impact on quality of life. Color vision was only selected by a small proportion of patients. Qualitative studies and patient testimonies describe a lifelong negative impact of the condition on education, employment opportunities, the ability to carry out daily activities and to travel; testimonies highlighted the burden on parental caregivers. However, the lack of qualitative studies of the impact of achromatopsia on patients’ quality of life and on society make it difficult to quantify the disease burden. No clinical guidelines were identified. With no treatment currently available, use of visual aids and adaptations is described as supportive care. Current literature describes a significant impact of achromatopsia on those affected; evidence of underdiagnosis suggests the societal burden may be more extensive than is recognized. Further studies are required to understand and quantify the economic and humanistic burden more fully.

Inner and Outer Retinal Contributions to Pupillary Light Response: Correlation to Functional and Morphologic Parameters in Glaucoma.

To evaluate in patients with primary open-angle glaucoma (POAG) the contribution of the inner and outer retinal photoreceptors to the pupillary light responses (PLRs) correlated with both functional (color vision and visual field perimetry) and morphologic (optical coherence tomography) parameters. In total, 45 patients with POAG and 25 healthy control participants were evaluated. The PLR was measured as pupil diameter with an eye tracker; stimuli were presented in a Ganzfeld. Pupil responses were measured monocularly, to 1 second blue (470 nm) and red (640 nm) flashes with -3, -2, -1, 0, 1, 2, and 2.4 log cd/m luminance levels. Color vision was evaluated with the Cambridge Color Test, visual field was measured by standard automatic perimetry, and retinal nerve fiber layer thickness was evaluated by optical coherence tomography. Patients with moderate and severe POAG have a significantly decreased PLR that depends on the severity of POAG, for both the 470 and 640 nm stimuli, revealing the reduction of the contributions of the rods, cones, and intrinsically photosensitive retinal ganglion cells to PLR. A significant loss of color discrimination along the blue-yellow axis was observed in all stages of POAG. Correlations among standard automatic perimetry, retinal nerve fiber layer thickness, Cambridge Color Test, PLR, and melanopsin parameters were found. The results provide evidence that in moderate and severe stages of POAG, both the inner and outer retinal contributions to PLR are affected. Also, a worsening in color vision was correlated with reduced PLR responses at high-intensity stimuli. These findings may enhance the clinical management of POAG patients.

The Verriest Lecture: Short-wave-sensitive cone pathways across the life span.

Structurally and functionally, the short-wave-sensitive (S) cone pathways are thought to decline more rapidly with normal aging than the middle- and long-wave-sensitive cone pathways. This would explain the celebrated results by Verriest and others demonstrating that the largest age-related color discrimination losses occur for stimuli on a tritan axis. Here, we challenge convention, arguing from psychophysical data that selective S-cone pathway losses do not cause declines in color discrimination. We show substantial declines in chromatic detection and discrimination, as well as in temporal and spatial vision tasks, that are mediated by S-cone pathways. These functional losses are not, however, unique to S-cone pathways. Finally, despite reduced photon capture by S cones, their postreceptoral pathways provide robust signals for the visual system to renormalize itself to maintain nearly stable color perception across the life span.

Homozygous missense variant in the human CNGA3 channel causes cone-rod dystrophy.

We assessed a large consanguineous Pakistani family (PKAB157) segregating early onset low vision problems. Funduscopic and electroretinographic evaluation of affected individuals revealed juvenile cone-rod dystrophy (CRD) with maculopathy. Other clinical symptoms included loss of color discrimination, photophobia and nystagmus. Whole-exome sequencing, segregation and haplotype analyses demonstrated that a transition variant (c.955T>C; p.(Cys319Arg)) in CNGA3 co-segregated with the CRD phenotype in family PKAB157. The ability of CNGA3 channel to influx calcium in response to agonist, when expressed either alone or together with the wild-type CNGB3 subunit in HEK293 cells, was completely abolished due to p.Cys319Arg variant. Western blotting and immunolocalization studies suggest that a decreased channel density in the HEK293 cell membrane due to impaired folding and/or trafficking of the CNGA3 protein is the main pathogenic effect of the p.Cys319Arg variant. Mutant alleles of the human cone photoreceptor cyclic nucleotide-gated channel (CNGA3) are frequently associated with achromatopsia. In rare cases, variants in CNGA3 are also associated with cone dystrophy, Leber's congenital amaurosis and oligo cone trichromacy. The identification of predicted p.(Cys319Arg) missense variant in CNGA3 expands the repertoire of the known genetic causes of CRD and phenotypic spectrum of CNGA3 alleles.

Correlations between color perception and motor function impairment in children with spastic cerebral palsy

IntroductionThe aim of the present study was to evaluate color perception thresholds and relate them to the degree of motor impairment in children with spastic cerebral palsy (SCP).MethodsBinocular and monocular chromaticity discrimination thresholds were estimated for the protan, deutan, and tritan color confusion axes in 43 SCP children aged 6–15 years who were classified as tetraplegic (n = 12), diplegic (n = 16), and hemiplegic (n = 15) without ophthalmological complaints. Motor impairment was rated according to the Gross Motor Function Classification System (GMFCS) in five levels of severity.ResultsAnalysis of variance showed significantly reduced discrimination in tetraplegic children (p < 0.001) compared with the diplegic, hemiplegic, and control groups. We also found a positive correlation between chromaticity discrimination thresholds and GMFCS ratings in all of the groups.DiscussionChromaticity discrimination thresholds measured psychophysically were reduced for all three color confusion axis in tetraplegic children compared with normal children. Diplegic and hemiplegic children had similar results as normal children. The finding of a correlation between quantified motor impairment and color discrimination losses in SCP patients is a new observation that might help elucidate the causes of color perception loss in these patients. Visual information is essential for the rehabilitation of CP children. Knowledge of the degree of correlation between vision and motor impairment is valuable when planning a rehabilitation program.

Early visual changes in diabetic patients with no retinopathy measured by color discrimination and electroretinography.

visual changes caused by diabetes include color vision losses and an abnormal full-field electroretinogram. The purpose of this study was to evaluate color vision in type 2 diabetic patients with no clinically detectable retinopathy using an objective psychophysical color vision test, evaluate retinal function assessed by full-field electroretinography ( ff ERG), and verify the agreement among the changes detected by each of these tests. Color vision was tested and ff ERG was performed in 34 diabetic patients (20 males; ages 56 ± 9 years). Results were compared with those obtained from age-matched control groups. Color discrimination losses occurred in all three color-confusion axes with a higher incidence on the protan axis. The full- field electroretinographic data indicated that inner retinal components (i.e., ff ERG oscillatory potentials) were more affected than outer retinal components, indicating impairment of second- and third-order retinal neurons early in the disease. Previous studies reported tritan losses as a classic color vision defect in diabetes, but our results showed that all three color-confusion axes (i.e., protan, deutan, and tritan) are compromised, at least during the very early stages of the disease, reflecting a diffuse pattern of color vision loss. The full-field electroretinographic results that showed abnormalities of the inner retina support the color vision findings. Keywords: color vision, psychophysics, diabetes mellitus, diabetic retinopathy, electroretinogram, visual electrophysiology, visual perception.

Restoration of Cone Vision in the CNGA3−/− Mouse Model of Congenital Complete Lack of Cone Photoreceptor Function

Congenital absence of cone photoreceptor function is associated with strongly impaired daylight vision and loss of color discrimination in human achromatopsia. Here, we introduce viral gene replacement therapy as a potential treatment for this disease in the CNGA3(-/-) mouse model. We show that such therapy can restore cone-specific visual processing in the central nervous system even if cone photoreceptors had been nonfunctional from birth. The restoration of cone vision was assessed at different stages along the visual pathway. Treated CNGA3(-/-) mice were able to generate cone photoreceptor responses and to transfer these signals to bipolar cells. In support, we found morphologically that treated cones expressed regular cyclic nucleotide-gated (CNG) channel complexes and opsins in outer segments, which previously they did not. Moreover, expression of CNGA3 normalized cyclic guanosine monophosphate (cGMP) levels in cones, delayed cone cell death and reduced the inflammatory response of Müller glia cells that is typical of retinal degenerations. Furthermore, ganglion cells from treated, but not from untreated, CNGA3(-/-) mice displayed cone-driven, light-evoked, spiking activity, indicating that signals generated in the outer retina are transmitted to the brain. Finally, we demonstrate that this newly acquired sensory information was translated into cone-mediated, vision-guided behavior.

Clinical and genetic investigation of a large Tunisian family with complete achromatopsia: identification of a new nonsense mutation in GNAT2 gene

Complete achromatopsia is a rare autosomal recessive disease associated with CNGA3, CNGB3, GNAT2 and PDE6C mutations. This retinal disorder is characterized by complete loss of color discrimination due to the absence or alteration of the cones function. The purpose of the present study was the clinical and the genetic characterization of achromatopsia in a large consanguineous Tunisian family. Ophthalmic evaluation included a full clinical examination, color vision testing and electroretinography. Linkage analysis using microsatellite markers flanking CNGA3, CNGB3, GNAT2 and PDE6C genes was performed. Mutations were screened by direct sequencing. A total of 12 individuals were diagnosed with congenital complete achromatopsia. They are members of six nuclear consanguineous families belonging to the same large consanguineous family. Linkage analysis revealed linkage to GNAT2. Mutational screening of GNAT2 revealed three intronic variations c.119-69G>C, c.161+66A>T and c.875-31G>C that co-segregated with a novel mutation p.R313X. An identical GNAT2 haplotype segregating with this mutation was identified, indicating a founder mutation. All patients were homozygous for the p.R313X mutation. This is the first report of the clinical and genetic investigation of complete achromatopsia in North Africa and the largest family with recessive achromatopsia involving GNAT2; thus, providing a unique opportunity for genotype-phenotype correlation for this extremely rare condition.

Red Light Increment Threshold as a Measure of Deficient Color Vision

People with deficient red/green color vision have both poor color discrimination and are also insensitive to colored lights, especially red, in an increment threshold situation. In this study we compare detection thresholds for a long wavelength increment to two standard color discrimination tests. Forty-five color normal subjects and 19 color-deficient subjects (CDs) (12 deutans, 4 protans, and 3 unclassified) were tested with the Hardy-Rand-Rittler (HRR) plate test (4th edition), Farnsworth D-15 arrangement test and a long wavelength increment threshold test, i.e., the red test. All CDs were less sensitive to the red increment than any of the normal subjects. The red test identified all CDs. There were no significant correlations between the red test results and the HRR test or the Farnsworth D-15 test. The red test measures red light increment threshold, a characteristic of color vision not assessed by conventional tests of color vision which are based upon measuring loss of color discrimination. All CD observers have raised red light increment thresholds and the test clearly differentiates CD observers from those with normal color vision.

Long-term loss of color vision after exposure to mercury vapor

We evaluated the color vision of 24 subjects (41.6 ± 6.5 years; 6 females) who worked in fluorescent lamp industries. They had been occupationally exposed to mercury vapor (10.6 ± 5.2 years) and had been away from the source of exposure for 6.4 ± 4.04 years. Mean urinary concentration of mercury was 40.6 ± 36.4 µg/g creatinine during or up to 1 year after exposure and 2.71 ± 1.19 µg/g creatinine at the time of color vision testing or up to 1 year thereafter. All patients were diagnosed with chronic mercury intoxication, characterized by clinical symptoms and neuropsychological alterations. A control group (N = 36, 48.6 ± 11.9 years, 10 females, 1.5 ± 0.47 µg mercury/g creatinine) was subjected to the same tests. Inclusion criteria for both groups were Snellen VA 20/30 or better and absence of known ophthalmologic pathologies. Color discrimination was assessed with the Farnsworth D-15 test (D-15) and with the Lanthony D-15d test (D-15d). Significant differences were found between the two eyes of the patients (P < 0.001) in both tests. Results for the worst eye were also different from controls for both tests: P = 0.014 for D-15 and P < 0.001 for D-15d. As shown in previous studies, the D-15d proved to be more sensitive than the D-15 for the screening and diagnosis of the color discrimination losses. Since color discrimination losses were still present many years after the end of exposure, they may be considered to be irreversible, at least under the conditions of the present study.

Long-term loss of color vision after exposure to mercury vapor

We evaluated the color vision of 24 subjects (41.6 +/- 6.5 years; 6 females) who worked in fluorescent lamp industries. They had been occupationally exposed to mercury vapor (10.6 +/- 5.2 years) and had been away from the source of exposure for 6.4 +/- 4.04 years. Mean urinary concentration of mercury was 40.6 +/- 36.4 microg/g creatinine during or up to 1 year after exposure and 2.71 +/- 1.19 microg/g creatinine at the time of color vision testing or up to 1 year thereafter. All patients were diagnosed with chronic mercury intoxication, characterized by clinical symptoms and neuropsychological alterations. A control group (N = 36, 48.6 +/- 11.9 years, 10 females, 1.5 +/- 0.47 microg mercury/g creatinine) was subjected to the same tests. Inclusion criteria for both groups were Snellen VA 20/30 or better and absence of known ophthalmologic pathologies. Color discrimination was assessed with the Farnsworth D-15 test (D-15) and with the Lanthony D-15d test (D-15d). Significant differences were found between the two eyes of the patients (P < 0.001) in both tests. Results for the worst eye were also different from controls for both tests: P = 0.014 for D-15 and P < 0.001 for D-15d. As shown in previous studies, the D-15d proved to be more sensitive than the D-15 for the screening and diagnosis of the color discrimination losses. Since color discrimination losses were still present many years after the end of exposure, they may be considered to be irreversible, at least under the conditions of the present study.

Compound heterozygous CNGA3 mutations (R436W, L633P) in a Japanese patient with congenital achromatopsia

Congenital achromatopsia is a stationary retinal disorder with autosomal recessive inheritance that is characterized by loss of color discrimination, low visual acuity, photophobia, and nystagmus. This disorder has been shown to be associated with CNGA3, CNGB3, and GNAT2 mutations, and the frequency of mutations in the CNGA3 gene (encoding alpha subunit of the cone-specific cGMP-gated cation channel) was 23-33% in European populations. The aim of this study was to test the hypothesis that CNGA3 mutations are also responsible for congenital achromatopsia in Japanese patients. DNA from venous blood samples from a total of 14 patients from 13 Japanese pedigrees was prepared. Mutation screening of the CNGA3 gene was performed using direct sequencing and PCR-single-strand conformation polymorphism analysis. Compound heterozygous missense mutations (p.R436W and p.L633P, the latter of which was novel) were identified in one patient only, a 22-year-old female. Neither of these two mutations was found in 150 Japanese control individuals. The patient's parents and sister carried one of these mutations each but were not affected. No mutations in the CNGB3 or GNAT2 genes were identified in the patient. Clinically, best-corrected visual acuity was 0.1 in both eyes. No specific findings were obtained in funduscopy. Optical coherence topography revealed a normal foveal thickness but a 20% decrease in parafoveal thickness. Ganzfeld full-field electroretinograms (ERGs) showed normal responses in rod and mixed rod-plus-cone ERGs but no response in cone or 30-Hz flicker ERGs. Spectral sensitivity on a white background revealed a curve with only one peak at around 500 nm, which fits the absorption spectrum of human rhodopsin. L633, conserved among vertebrate orthologs of human CNGA3, is a hydrophobic residue forming part of the carboxy-terminal leucine zipper (CLZ) domain, which is functionally important in the mediation of intracellular interactions. To our knowledge, this is the first report of a Japanese complete achromat with CNGA3 mutations, and of any patient with a missense mutation within the CLZ domain. The outcome suggests low frequency (7%, 1/14) of CNGA3 mutations in Japanese patients.

Idiopathic Photoreceptor Dysfunction Causes Unexplained Visual Acuity Loss in Later Adulthood

Progressive visual loss, caused by initially unrecognized retinal photoreceptor dysfunction predominantly affecting cones, developed in six patients in late adulthood. Because of minimal ophthalmoscopic retinal abnormalities, the patients initially had been suspected of having optic neuropathy or psychogenic visual loss. The correct diagnosis was ultimately established by finding electroretinographic abnormalities and color discrimination losses out of proportion to visual acuity loss. In no case was a causative agent or a family history of photoreceptor disease identified. In many other respects, however, features of the patients' illness resemble those described previously under the headings of cone dysfunction syndrome, cone dystrophy, cone degeneration, and conerod dystrophy.

Physical characteristics and perceptual effects of "blue-blocking" lenses.

The transmission-optical properties of a "blue-blocking" lens and its influence on several aspects of human visual performance were assessed. Results showed that the lens was effective in absorbing ultraviolet and blue wavelengths and that its effects on contrast sensitivity and visual evoked potentials (VEP's) were similar to those produced by an equivalent neutral density (ND) filter. Although the lens did not alter stereopsis, it did produce severe color discrimination losses for normal and dichromatic subjects.

Color discrimination and neural coding in color deficients

Rayleigh color match ranges obtained from color deficient observers varied considerably as a function of spatial and temporal parameters of stimulus presentation. The results suggest that color discrimination losses in color deficients result from abnormalities in the spatial and temporal properties of neural coding in addition to cone photopigment abnormalities.

Red-green mixture thresholds in congenital and acquired color defects

A color television display was used to measure thresholds for mixtures of red and green on a white background; red and green components could be either incremental, decremental or zero. Ellipses are fitted to a plot of green contrast as a function of red contrast, and it is argued that the length of the ellipse is a measure of red-green color discrimination and the width of the ellipse is a measure of luminance discrimination. It is shown that the technique reliably distinguishes normals from congenital color defectives and also protan from deutan subjects. For some cases of acquired color defects (e.g. optic neuritis), there is a roughly equal loss of color and luminance discrimination whereas, in other cases (e.g. hereditary optic atrophies), the loss of color discrimination is much greater than the loss of luminance discrimination.

Color discrimination on Mangaia

Bornstein’s hypothesis that there is a loss of color discrimination in tropical areas was not supported in earlier research in the Cook Islands. Using a more sensitive color vision test (the Farnsworth-Munsell 100-Hue Test), a loss of color discrimination in the red-purple and blue-green regions of the spectrum was found. The lack of sex differences in this color discrimination loss supports a physiological rather than a genetic explanation of the observed decrement.

Color-vision mechanisms of the extrafoveal retina

Wavelength discrimination, spectral sensitivity as well as color-matching performance were measured at the fovea and at different eccentricities in the peripheral retina. The results show that the underlying mechanisms of color vision in the normal peripheral retina are different from those of the classic forms of congenital color blindness. On the other hand, a close correspondence was found between color-vision characteristics obtained in the extrafoveal retina and in patients with acquired color-vision defects due to diseases of the optic nerve, suggesting that the loss of color discrimination with eccentricity and during progression of these diseases has a common underlying basis.

Loss of Color Discrimination under Reduced Visual Conditions

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text , "Loss of Color Discrimination under Reduced Visual Conditions," Appl. Opt. 8, 1858-1858 (1969) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article