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At least 559 records · Page 31Linked to original sources
PubMed2001

Color vision deficiencies in Gilles de la Tourette syndrome.

Color perception was tested using the Farnsworth-Munsell 100-Hue Test in a sample of persons with Gilles de la Tourette syndrome (GTS), and compared to norms from three age cohorts in the early second, fourth and sixth decades. Red-green color errors on the Farnsworth-Munsell did not appear to change appreciably as a function of age or GTS. Blue-yellow error scores did, however, increase with age and were exaggerated in the GTS group. It is concluded that sensory and perceptual disturbances are present in GTS as in other basal cell ganglia disorders. The results are discussed in terms of converging retinal dopaminergic mechanisms also associated with Parkinson's and Huntington's diseases and even with normal aging. Suggestions are offered that daily activities and behavior may be affected by spatial and chromatic deficiencies.

Adult↗
PubMed1986

Color vision and retinal nerve fiber layer in early glaucoma.

We tested 47 eyes in 47 patients (ten normal subjects, 15 with suspected glaucoma, and 22 with glaucoma) with the Pickford-Nicholson anomaloscope to assess the retinal nerve fiber layer and measure color vision. The 47 subjects were randomly selected from a group of 132 for whom Farnsworth-Munsell 100-hue color error scores were known. The yellow-blue and green-blue anomaloscopic matching ranges correlated significantly with diffuse retinal nerve fiber loss. There was no correlation with localized retinal nerve fiber loss.

Adult↗
PubMed1993

Identification of the Cl(-)-binding site in the human red and green color vision pigments.

Chloride ions are known to bind and alter the absorption spectra of some but not all visual pigments. In this report, the human red and green color vision pigments are shown to bind Cl- and to undergo a large red shift in their absorption maxima. Mutation of 18 different positively charged amino acids in these pigments identified two residues, His197 and Lys200, in the Cl(-)-binding site. His197 and Lys200 are strictly conserved in all long-wavelength cone pigments but are absent in all rhodopsins and short-wavelength cone pigments. This fact suggests that the evolutionary branch of the long-wavelength pigments was established when an ancestral pigment acquired the ability to bind Cl- and, as a result, shift the absorption maximum to longer wavelengths.

Amino Acid Sequence↗
PubMed1997

Unexpected conservation of the X-linked color vision gene in nocturnal prosimians: evidence from two bush babies.

Bush babies have had a long history of nocturnal life and it would be interesting to know whether their color vision genes have become degenerate. Therefore, we used PCR techniques to sequence the X-linked pigment gene of two of these nocturnal prosimians: Galago senegalensis and Otolemur garnettii. Southern hybridization of genomic DNA of G. senegalensis showed a single X-linked pigment gene. Interestingly, the deduced pigment sequences of the two bush babies are identical. By comparing the X-linked pigments of bush baby, human, squirrel monkey, and marmoset, 38 variable positions were identified. At those positions that may cause a spectral shift, the bush baby pigment has identical or biochemically similar residues to those of the marmoset cone pigment with a spectral peak of 543 nm. This result is consistent with the estimate of 544-545 nm for the spectral peak of the X-linked pigment of Otolemur crassicaudatus, which is closely related to Otolemur garnettii. The neighbor-joining tree of mammalian X-linked pigments showed a significantly shorter branch in the bush baby lineage than in other primate lineages. A relative rate test showed that the nonsynonymous substitution rate of the bush baby X-linked pigment gene is about three times slower than that of the human red pigment gene, though the synonymous substitution rates of the two genes are similar. The slower nonsynonymous rate in the bush baby lineage suggests that the bush baby X-linked pigment gene is under functional constraints, in spite of its nocturnal life. Two radical changes at positions in the intradiskal surface next to the sixth transmembrane domain were observed in the X-linked cone pigment of bush babies but not in other primates. They are changes from Ala to Ser and from Asn to His, which are similar in function to the corresponding residues in rhodopsins. These two changes may be of importance for dim light sensitivity, which is consistent with our proposal that the evolution of the bush baby X-linked pigment gene is under selective pressure. In addition, the 2.5% divergence in introns 2 and 5 of the X-linked pigment gene between the two bush babies supports their classification into two separate genera.

Adaptation, Physiological↗
PubMed1992

Absorption spectra of the hybrid pigments responsible for anomalous color vision.

Unequal homologous recombination events between green and red cone pigment genes produce the red-green or green-red hybrid pigment genes found in many individuals with variant color vision. Photobleaching difference absorption spectroscopy of hybrid pigments produced in cultured cells shows that the spectral sensitivity of each hybrid pigment is intermediate between the parental green and red pigment sensitivities. Amino acids encoded by exons 2, 3, 4, and 5 produce spectral shifts at the wavelength of maximal absorbance of 0 to 4, 0 to 4, 3 to 4, and 15 to 21 nanometers, respectively, the exact value depending on the identities of amino acids elsewhere in the hybrid.

Color Perception↗
PubMed1988

Rods also participate in human color vision.

In the retinal periphery, rod and cone thresholds to the same green light were measured. After the rod-cone break in the course of dark adaptation, cone sensitivity decreases gradually as rod sensitivity progressively increases. Cone sensitivity, however, increases when rod sensitivity is decreased by blue light. The emergence of the facilitatory effect of rod activation requires at least a few hundred msec after rod stimulation. It is concluded that rod activation plays a major role in sensitivity regulation of the cone system, i.e., in human color vision.

Color Perception↗
PubMed1986

Spectral mechanisms and color vision in the tree shrew (Tupaia belangeri).

The retina of the tree shrew (Tupaia belangeri) is heavily cone dominated, rods comprising less than 4% of the total photoreceptors. Spectral mechanisms and color vision were investigated in this species in both behavioral and electrophysiological experiments. In confirmation of an earlier investigation, the tree shrew was found to have a clear spectral neutral point (at ca 505 nm) and is thus a dichromat. Spectral sensitivity functions determined in an increment threshold discrimination task show two clear peaks (at ca 440 and 550-560 nm) with an intermediate region of lowered sensitivity centered at about 500 nm. Spectral sensitivity of the two cone types in this animal were determined using ERG flicker photometry. One of these cone classes has a peak at 556 nm; the other has a 444 nm peak.

Animals↗
PubMedDate not supplied

Prediction of diabetic retinopathy from clinical variables and color vision data.

Predictions about the onset of retinopathy in 295 diabetic patients, all originally having no evidence of retinopathy, have been made in a longitudinal study over 7 yr. Out of many color vision tests and clinical variables, the best individual predictor was a measure of yellow-blue discrimination, using an anomaloscope. The other predictors of significance were the degree of blood glucose control and the duration of diabetes. Although the predictions from a linear logistic model were significant in classifying the diabetic subjects into those whose fundus will remain normal and those in whom it will develop retinopathy, the number of misclassifications was substantial. An examination of the goodness of fit between the data and the model suggested a criterion value (P) of around P = 0.3 for the probability that a patient develops retinopathy. At this value, the probability of being normal for an individual classed as normal was 0.82, and the probability of developing retinopathy for an individual classed as having retinopathy was 0.54.

Adult↗
PubMed1975

Color vision and brightness discrimination in two-month-old human infants.

A red or white bar, embedded in a white screen, was systematically varied in intensity. Infants consistently located and stared at the white bar unless it closely matched the screen in intensity. They also stared at all intensities of the red bar, presumptively including the red-white brightness match, and hence must have some form of color vision.

Color Perception↗
PubMed1999

Color vision deficits and laser eyewear protection for soft tissue laser applications.

PURPOSE: Laser safety considerations require urologists to wear laser eye protection. Laser eye protection devices block transmittance of specific light wavelengths and may distort color perception. We tested whether urologists risk color confusion when wearing laser eye protection devices for laser soft tissue applications. MATERIALS AND METHODS: Subjects were tested with the Farnsworth-Munsell 100-Hue Test without (controls) and with laser eye protection devices for carbon dioxide, potassium titanyl phosphate (KTP), neodymium (Nd):YAG and holmium:YAG lasers. Color deficits were characterized by error scores, polar graphs, confusion angles, confusion index, scatter index and color axes. Laser eye protection device spectral transmittance was tested with spectrophotometry. RESULTS: Mean total error scores plus or minus standard deviation were 13+/-5 for controls, and 44+/-31 for carbon dioxide, 273+/-26 for KTP, 22+/-6 for Nd:YAG and 14+/-8 for holmium:YAG devices (p <0.001). The KTP laser eye protection polar graphs, and confusion and scatter indexes revealed moderate blue-yellow and red-green color confusion. Color axes indicated no significant deficits for controls, or carbon dioxide, Nd:YAG or holmium:YAG laser eye protection in any subject compared to blue-yellow color vision deficits in 8 of 8 tested with KTP laser eye protection (p <0.001). Spectrophotometry demonstrated that light was blocked with laser eye protection devices for carbon dioxide less than 380, holmium:YAG greater than 850, Nd:YAG less than 350 and greater than 950, and KTP less than 550 and greater than 750 nm. CONCLUSIONS: The laser eye protection device for KTP causes significant blue-yellow and red-green color confusion. Laser eye protection devices for carbon dioxide, holmium:YAG and Nd:YAG cause no significant color confusion compared to controls. The differences are explained by laser eye protection spectrophotometry characteristics and visual physiology.

Adult↗