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Results for “Color Vision”

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At least 613 records · Page 34Linked to original sources
PubMed1992

Abnormalities in color vision and contrast sensitivity in Parkinson's disease.

Dopamine is a neurotransmitter found in the retina. Delays in the visual evoked responses and abnormalities in contrast sensitivity occur in patients with Parkinson's disease. Improvement in the P100 has followed L-dopa therapy. Suspected abnormalities at the retinal level in Parkinson's disease are observed in reductions in photopic, scotopic, and pattern-derived electroretinograms. We studied 35 patients with Parkinson's disease and 26 controls of comparable age and visual acuities using visual evoked responses, color vision, and contrast sensitivity testing. Contrast sensitivity thresholds were significantly different at most frequencies tested, using both stationary and temporally modulated sinusoidal gratings. The total error score of the Farnsworth-Munsell 100 Hue Test revealed significant differences between the patients and controls. The contrast thresholds derived from certain spatial frequencies and the total error in color score were significantly related to the duration of disease. A stepwise discriminant analysis correctly identified 94% of the patients and 94% of the controls. The significant error in chromatic discrimination observed in Parkinson's disease patients may be due to altered intraretinal dopaminergic synaptic activity in these patients.

Color Perception↗
PubMed1988

[The course of color vision in early diabetic retinopathy treated with Ginkgo biloba extract. A preliminary double-blind versus placebo study].

The therapeutic efficiency of the Ginkgo biloba extract was estimated in a double-blind trial, during a 6 months period, in 29 diabetic subjects with an early diabetic retinopathy evidenced by angiography, and associated with a blue-yellow dyschromatopsia. The functional criterion was the color vision evolution, studied by the Desaturated Panel D-15 and the 100-Hue Farnsworth test at the beginning of the trial and 6 months later. An improvement tendency was evidenced in subjects treated by Ginkgo biloba extract, and an aggravation in subjects with placebo, this improvement being statistically significative with the Desaturated Panel D-15 among subjects without retinal ischemia. These clinical results on visual function corroborate the pharmacological actions of Ginkgo biloba extract on diabetic retina.

Clinical Trials as Topic↗
PubMedDate not supplied

Photopigment basis for dichromatic color vision in cows, goats, and sheep.

Electroretinogram (ERG) flicker photometry was used to measure the spectral properties of cones in three common ungulates-cattle (Bos taurus), goats (Capra hircus), and sheep (Ovis aries). Two cone mechanisms were identified in each species. The location of peak sensitivity of an S-cone mechanism varied from about 444 to 455 nm for the three species; analogous values for an M/L-cone were tightly clumped at about 552-555 nm. Each of these three species has the requisite photopigment basis for dichromatic color vision and they are, thus, similar to other ungulates examined earlier.

Animals↗
PubMed1993

Actin-binding protein (ABP-280) filamin gene (FLN) maps telomeric to the color vision locus (R/GCP) and centromeric to G6PD in Xq28.

Actin-binding protein-280 (ABP-280) is a dimeric actin filament crosslinking protein that promotes orthogonal branching of actin filaments and links actin filaments to membrane glycoproteins. We have mapped the ABP-280 filamin gene (FLN) to Xq28 by Southern blot analysis of somatic cell hybrid lines, by fluorescence in situ hybridization, and through identification of portions of the FLN gene within cosmids and YACs mapped to Xq28. The FLN gene is found within a 200-kb region centromeric to the G6PD locus and telomeric to DSX52 and the color vision locus.

Blotting, Southern↗
PubMed1994

Systematic measurement of human neonatal color vision.

We used a new time-efficient method to evaluate chromatic-achromatic discrimination in newborn (n = 36) and 1-month-old (n = 34) human infants. Results showed that 74% of newborns discriminated a 10.5 x 17.5 deg broadband red patch from all relative luminances of an achromatic background, but only 14% of newborns did so with a blue, 36% with a green, and 25% with a yellow patch. Most infants who "failed" did so at relative luminances very close to the respective photopic luminance match. At 1 month, performance improved somewhat although infants still show clear evidence of discriminating only the red patch. These results, the first to be obtained from individual newborns with a method incorporating a systematic variation of luminance, imply that early color vision is very limited. Possible photoreceptoral and neural bases for these immaturities are discussed.

Child Development↗
PubMed1997

Mutation of a conserved cysteine in the X-linked cone opsins causes color vision deficiencies by disrupting protein folding and stability.

PURPOSE: To test the effects of disruption of a conserved cysteine in the green cone opsin molecule on light-activated isomerization, transducin activation, folding, transport, and protein half-life. METHODS: Stable cell lines were established by transfecting 293-EBNA cells with a plasmid containing wild-type or mutant (C203R, C203S, C126S, C126S/C203S) green opsin cDNA molecules. The proteins were induced by culturing the cells in the presence of cadmium chloride and analyzed by spectra, transducin activation, Western blotting, pulse-labeling with immunoprecipitation, and immunocytochemistry. RESULTS: The C203R mutation disrupts the folding and half-life of the green opsin molecule and its abilities to absorb light at the appropriate wavelength and to activate transducin. Similar disruption of folding, half-life, and light activation occurs when Cys203 or its presumed partner for formation of a disulfide bond (Cys126) is replaced by serine residues. CONCLUSIONS: Like rhodopsin, the folding of the cone opsins appears to be dependent on the formation of a disulfide bond between the third transmembrane helix and the second extracellular loop. Disruption of this disulfide bond represents a cause of color vision deficiencies that is unrelated to spectral shifts of the photopigment.

Amino Acid Sequence↗
PubMed1998

Variations in cone populations for red-green color vision examined by analysis of mRNA.

In the central human retina, there are estimated to be nearly two L cone photoreceptors for each M cone. The extent to which this value varies across individuals is unclear and little is known about how the M:L cone ratio might change with retinal location. To address these questions, the ratio of M:L cone pigment mRNA was examined at different locations. For patches of central retina, the average M:L ratio was about 2:3 which decreased to about 1:3 for patches 40 degrees eccentric. There were also large individual differences among the 23 eyes examined. The extremes differed in central M:L mRNA ratio by a factor of > 3. The measured differences in mRNA ratio are proposed to reflect differences in photoreceptor ratio. Such variations provide unique opportunities for understanding how the neural circuitry for color vision is affected by changes in cone ratio.

Adolescent↗
PubMed1997

Infant color vision: temporal contrast sensitivity functions for chromatic (red/green) stimuli in 3-month-olds.

In order to investigate the development of temporal contrast sensitivity functions (tCSFs) for chromatic (red/green) stimuli, we obtained chromatic contrast thresholds from 3-month-old infants and adults using behavioral techniques. Stimuli were moving or counterphase-reversing sinusoidal gratings of 0.25 c/deg. Five temporal frequencies were used: 0.7, 2.1, 5.6, 11 and 17 Hz (corresponding speeds = 2.8, 8.4, 22, 44 and 67 deg/sec). In order to compare chromatic results with those obtained under luminance-defined conditions, luminance tCSFs were also obtained from adults, and previously obtained infant luminance tCSFs were used (from Dobkins & Teller, 1996a). In accordance with previous studies, adults exhibited bandpass luminance tCSFs with peaks near 5 Hz and lowpass chromatic tCSFs that declined rapidly at temporal frequencies greater than 2 Hz, and the two curves crossed one another near 4 Hz. By contrast, infants exhibited bandpass rather than lowpass chromatic tCSFs with peaks near 5 Hz. These chromatic curves were quite similar in peak frequency and general shape to previously obtained infant tCSFs for luminance stimuli. Moreover, both chromatic and luminance tCSFs in infants were found to be quite similar in peak and shape to luminance tCSFs observed in adults. These findings point to the possibility that, for 3-month-old infants, both chromatic and luminance stimuli are detected by the same underlying mechanism under these conditions. We propose that such a mechanism is probably a physiological pathway dominated by magnocellular input. Earlier studies of infant color vision are discussed in this context.

Adult↗
PubMed2006

Color vision in the giant panda (Ailuropoda melanoleuca).

Hue discrimination abilities of giant pandas were tested, controlling for brightness. Subjects were 2 adult giant pandas (1 male and 1 female). A simultaneous discrimination procedure without correction was used. In five tasks, white, black, and five saturations each of green, blue, and red served as positive stimuli that were paired with one or two comparison stimuli consisting of 16 saturations of gray. To demonstrate discrimination, the subjects were required to choose the positive stimulus in 16 of 20 trials (80% correct) for three consecutivesessions. Both subjects reached criterion forgreen and red. The female subject also reached criterion for blue. The male was not tested for blue. This study is a systematic replication of Bacon and Burghardt's (1976) color discrimination experiment on black bears. The results suggest that color vision in the giant panda is comparable to that of black bears and other carnivores that are not strictly nocturnal.

Animals↗
PubMed1991

[The color vision in patients with optic neuritis and chronic open-angle glaucoma].

Twenty eight cases (50 eyes) of chronic open-angle glaucoma and 21 cases (27 eyes) of optic neuritis were investigated with FM 100-hue test and panel D-15 test. In patients with optic neuritis, 70.37% and 85.19% of the affected eyes appeared abnormal in Panel D-15 test and FM 100-hue test respectively. The main defects were tritan-like in both of the tests. In patients with chronic open-angle glaucoma, 20% and 32% of the affected eyes had abnormal results in Panel D-15 test and FM 100-hue test respectively. The main defects were also tritan-like color vision defect. The total error scores of FM 100-hue test in patients with chronic open-angle glaucoma had no relation with the cup disc ratio and the area of peripheral visual field but had relation with the area of central visual field.

Adolescent↗