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At least 865 records · Page 48Linked to original sources
PubMed1991

Color vision following intense green light exposure: data and a model.

Hue discrimination, spectral sensitivity, and mathematical models of both are presented for a rhesus monkey which was exposed to intense green light. One of the monkey's eyes was blue-blinded in a previous experimental procedure and the other was color normal. The results of green light exposure showed a loss of sensitivity on both measures, with greater loss in the blue-blinded eye. Although there was considerable loss of hue-discrimination in the blue-green spectral regions, hue-discrimination at the point of best discrimination, 590 nm, remained unaffected. This pattern of results poses difficulties for models of hue discrimination, and has resulted in the proposed model employing three opponent color channels. The number of free-parameters are minimized and the integration between spectral sensitivity and hue discrimination enhanced by deriving parameters used in modeling hue discrimination from spectral sensitivity or vice versa.

Animals↗
PubMed1989

[Screening of early color vision loss in diabetic patients].

Colour vision defects have been claimed to appear in diabetes before any retinopathy is visible. In the present study diabetic patients and non diabetic control subjects were screened with two different colour vision tests which include both red-green and blue-yellow parts, and are suitable for quantitative analysis of scores. The Lanthony 40 Hue test and the Tokyo Medical College--T.M.C. tables were used to assess colour vision in 106 diabetic (50 insulin dependent and 56 non insulin dependent) patients and in 99 non diabetic control subjects. Diabetic patients without visible retinopathy, familiar colour vision defects and/or lens changes, had significantly higher scores than control subjects in both eyes. The differences were more evident in non insulin dependent patients. Statistical analysis showed that early loss of colour vision was correlated with age and duration of diabetes for older patients, while correlation with glycosylated hemoglobin was moderately positive only for younger patients. Both tests (especially the Lanthony 40 Hue) resulted to be highly specific and could be used for the clinical study of colour vision losses in diabetic patients.

Adult↗
PubMedDate not supplied

[A model of color vision in trichromats and protans].

A model which explains the human vision protanopic deficiency and its biologic prototype with the absence of red-absorbing pigment (rabbit) was constructed from neuron-like elements. In behavioral experiments and by means of evoked potential technique it was shown that the rabbit's color space is characterized by a spherical four-dimensional with a reduction of red-coding area. Similar spherical four-dimensional structure of color space is characteristic for a group of protanopic human subjects. The perceptive space of another group of protanopic subjects (protanomals) is characterized by a reduction of both parts of the red-green opponent axis. These disorders are reproduced in the model either by a loss of some color-coding elements (the absence of the red-absorbing pigment as in protanops) or a shift of the spectral characteristics of the red pigment towards those of the green one (protanomals).

Animals↗
PubMed2002

[Color vision defects in patients with arterial hypertension].

PURPOSE: In view of the generally impaired vascular condition in patients with arterial hypertension, we were interested in their colour perception. METHODS: Patients (n = 35, f:m = 14:21, mean age 52 +/- 11 years) with arterial hypertension without damage in end-organs and normal subjects (n = 62, :m = 28:34, mean age 49 +/- 9 years) as a control group were included in this study. Exclusion criteria were other systemic or ophthalmological diseases. In addition to the ophthalmological examinations (visual acuity, refraction, intraocular pressure, slit lamp and fundus examination) the colour vision was tested by the colour arrangement test Roth 28-hue (E) desaturated under standard conditions: The background used was black cardboard, illuminated by two Osram fluorescent lamps (L36 W/12LDL Daylight) providing 2000 lux at the test table. RESULTS: The ophthalmological examinations in the patients and in the control group were normal. The patients with arterial hypertension had a significantly higher mean error score (median +/- mean absolute deviation 150 +/- 56, Mann-Witney U-test: p < 0.001) in the colour arrangement test than the control group (median +/- mean absolute deviation 72 +/- 53.4). A particular colour axis (blue-yellow or red-green) was not found. CONCLUSION: Although the ophthalmological examinations were normal we found a disturbed colour vision in patients with arterial hypertension. This has to be taken into account in colour vision testing to avoid diagnostic interferences between specifically ocular diseases (e.g. glaucoma) and arterial hypertension.

Adult↗
PubMed1980

Loss of color vision and Stiles' II1 mechanism in a patient with cerebral infarction.

A 70-year old man developed achromatopsia with bilateral loss of superior visual fields and an inability to recognize familiar faces (prosopagnosia). Ophthalmologic examination results were normal. Visual acuity was 20/25 in either eye. Computerized axial tomography of the brain revealed infarction of the inferior aspect of the temporal occipital cortex in both hemispheres. The patient's complaint that objects appeared only in shades of gray was supported by large errors made throughout the spectrum on the Farnsworth-Munsell 100 hue test and by matches over the entire red/green range on the Nagel anomaloscope. Although absolute scotopic and photopic thresholds were unremarkable, the increment thresholds to a 482-nm test on a red background increased monotonically as if the II1 mechanism were absent. In addition, the spectral sensitivity to large test flashes on an intense red background peaked in the middle rather than in the short-wave portion of the spectrum, as is normally found. We speculate that the chromatic channel is compromised. The patient's residual vision is mediated by a luminance channel that is subserved by the middle and long--but not the short--wave cone mechanisms.

Aged↗
PubMed2000

Variations in normal color vision. II. Unique hues.

We examined individual differences in the color appearance of nonspectral lights and asked how they might be related to individual differences in sensitivity to chromatic stimuli. Observers set unique hues for moderately saturated equiluminant stimuli by varying their hue angle within a plane defined by the LvsM and SvsLM cone-opponent axes that are thought to characterize early postreceptoral color coding. Unique red settings were close to the +L pole of the LvsM axis, while green, blue, and yellow settings clustered along directions intermediate to the LvsM and SvsLM axes and thus corresponded to particular ratios of LvsM to SvsLM activity. Interobserver differences in the unique hues were substantial. However, no relationship was found between hue settings and relative sensitivity to the LvsM and SvsLM axes. Moreover, interobserver variations in different unique hues were uncorrelated and were thus inconsistent with a common underlying factor such as relative sensitivity or changes in the spectral sensitivities of the cones. Thus for the moderately saturated lights we tested, the unique hues appear largely unconstrained by normal individual differences in the cone-opponent axes. In turn, this suggests that the perceived hue for these stimuli does not depend on fixed (common) physiological weightings of the cone-opponent axes or on fixed (common) color signals in the environment.

Color↗
PubMedDate not supplied

Early loss of blue-sensitive color vision in patients with type I diabetes.

Existing methods for early detection of ocular injury from diabetes have serious limitations. We describe a new method, measuring visual flicker discrimination of the blue-sensitive mechanism of vision. This method is noninvasive, quantitative, and capable of distinguishing two types of impairment. Blue-flicker discrimination was measured in 10 adults with type I (insulin-dependent) diabetes for less than 5 yr. Although no evidence of diabetic changes was detected by careful ophthalmic examination by an experienced ophthalmologist, 12 of 19 eyes (63%) had flicker discrimination scores considered abnormal in comparison with those of a control group, and 8 of 10 subjects (80%) had at least 1 eye with abnormal performance. In all but 2 abnormal eyes the deficit of blue-flicker discrimination was of the "absorptive" type, suggesting increased absorbance or scattering of blue light in the optical media. These data show that a functional impairment of vision can be measured very early in the course of type I diabetes, before visible retinopathy is present, and suggest this test procedure may have both investigative and clinical applications.

Adult↗