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Results for “Color Vision Defects”

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PubMed1986

Flicker electroretinogram in retinitis pigmentosa.

Electroretinograms (ERGs) were recorded as a function of flicker frequency from 5 to 50 Hz for 14 retinitis pigmentosa (RP) patients, 12 normal subjects and 1 rod monochromat. Data were analyzed by measuring the angular position of the response maximum, i.e. the phase, as a function of pulse-train frequency. Flicker ERGs obtained from the RP patients showed non-linear, frequency-dependent phase shifts when compared to the normal data. These phase shifts were simulated in a normal observer by attenuating the stimulus luminance by 1 log unit. However, the shape of the waveforms recorded from the normal differed markedly from those recorded from the RP patients. The differences, but not the ratios of the times-to-peak of the positive and negative ERG wavelets were longer in the RP patients than in the normal. These data suggest that the temporal anomalies in the RP flicker ERG are most likely due to changes in the amplitudes and time constants of the ERG components, and not simply to a reduced quantum catch or photoreceptor loss.

Adolescent↗
PubMed1986

Light induced oscillations of the standing potential in achromatopsia.

In three children with achromatopsia light-induced oscillations of the standing potential and electroretinograms (ERGs) were recorded. A low drift direct current recording system was applied to monitor the changes of the standing potential under general anesthesia. In all children the scotopic ERG components were normal. No photopic components could be observed. The fast oscillations of the standing potential were normal under scotopic and photopic conditions. The light-induced slow increase of the standing potential displayed low amplitudes and normal peak latencies. The results of our study support earlier investigations suggesting that cone-mediated mechanisms in the retina contribute a significant component to the amplitude of the light peak in the electroretinogram.

Child, Preschool↗
PubMed1986

Chronic carbon disulphide poisoning: a 4 year follow-up study of the ophthalmological signs.

Thirty workers of a viscose rayon industry had a complete eye examination in 1979 including visual acuity, perimetry, colour vision testing, fluorescein angiography, ERG and EOG, for possible signs of chronic carbon disulphide poisoning. They were divided into two groups, group A included workers exposed to relatively high CS2 levels (at least 50 mg/m3), group B working in the relatively safe bleaching division. In both groups fundus anomalies and abnormal EOG's en ERG's were found. Twenty-nine of these thirty workers were reexamined in 1983. A number of them were no longer exposed to CS2 for a period varying between 1 and 43 months. The fundus signs (pigmentary changes and vascular lesions) increased in frequency, even if the patient was no longer exposed. The light/dark ratio of the EOG after 4 years was decreased in comparison with the first EOG, although this was not statistically significant. The ERG improved on follow-up. This could be related either to a shift to supranormal amplitudes or to recovery from subnormal amplitudes after the patient was no longer exposed.

Carbon Disulfide↗
PubMed1984

Localisation of the Becker muscular dystrophy gene on the short arm of the X chromosome by linkage to cloned DNA sequences.

A linkage study in 30 Becker muscular dystrophy (BMD) kindreds using three cloned DNA sequences from the X chromosome which demonstrate restriction fragment length polymorphisms (RFLPs), suggests that the BMD gene is located on the short arm of the X chromosome, in the p21 region. The genes for Becker and Duchenne dystrophies must therefore be closely linked, if not allelic, and any future DNA probes found to be of practical use in one disorder should be equally applicable to the other. The linkage analysis also provides data on the frequency of recombination along the short arm of the X chromosome, and across the centromeric region.

Blood Group Antigens↗
PubMed1984

Old and new genetics help ordering loci at the telomere of the human X-chromosome long arm.

A Sardinian pedigree described in 1964 for having been found to segregate at the X-linked loci for the Xga antigen, G6PD deficiency, Protan and Deutan color blindness, with an instance of recombination between the last two loci, was re-examined with respect to four common X-linked DNA polymorphisms detected by molecular probes homologous to critical subregions of the human X chromosome. Two branches of this pedigree--including the one with the Protan-Deutan recombinant--were found to segregate also for the common BamHI polymorphism identified with the cDNA probe pHPT-2 or the HPRT gene (Xq26). The analysis of the chromosome haplotypes in the male offspring of the phase known penta-heterozygous mother suggests that the probable order of the relevant loci is HPRT, Deutan, G6PD, Protan, Xq telomere. Though we are fully aware of the risks of generalizing the significance of observations made on a single exceptional pedigree, we believe that this report outlines the potential of families of the type described as research tools to resolve the linear order of tightly X-linked loci and to investigate the biology of genetic recombination in humans.

Blood Group Antigens↗
PubMed1976

[Evidence for reduced colour vision in carriers of congenital colour vision deficiencies (author's transl)].

The ability to recognize small spots of coloured light in parafoveal regions of the retina was investigated in women heterozygous for protanopia (2 subjects), deuteranopia (2 subjects), or deuteranomaly (1 subject) and in 3 normal subjects. The homozygous colour normals had excellent discrimination up to 8 degrees excentricity, whereas in heterozygous carriers of congenital colour vision deficiencies the ability to differentiate colours varied from point to point within the retina. The results may be explained by assuming the existence of alternating patches of trichromatic and dichromatic cell populations with the retina of the heterozygous carriers.

Color Perception↗
PubMed1982

Psychopatho-ophthalmology, gnostic disorders, and psychosis in cardiac surgery. Visual disturbances after open heart surgery.

The visual disturbances of 45 patients following open heart surgery could be divided into disturbances of (1) visual acuity, (2) visual accuracy, and (3) visual reality testing. The non-hallucinatory phenomena consisted mainly of loss of colour vision, metamorphopsias, visual gnostic disorders and cortical blindness. The hallucinatory phenomena could be divided into the delirium type of hallucinations with clouding of consciousness and the spectator type of hallucinations with a clear sensorium. The causes of the visual symptomatology and cardiac psychoses are seen in microembolization and/or ischemic hypoxia. The basal ganglia and the occipital lobe are areas of predilection for embolic and hypoxic changes. Identical psychoses also occur in cerebral malaria and polycythemia vera which show the same embolic and anoxic neuropathological changes of vascular occlusion as do many patients who die following open heart surgery with extracorporal circulation.

Agnosia↗
PubMed1978

Association and dissociation of visual functions in a case of bilateral occipital lobe infarction.

A severe restriction of the visual field was observed in a patient suffering a bilateral occipital lobe infarction. Soon after the lesion, the visual field had an angle of approx. 4 degrees. Some recovery was observed within the following months. Within the restricted visual field, several visual functions were tested. Increment threshold, for instance, was found to be one log unit higher than would normally be expected. Color vision was completely lost soon after the lesion, but some recovery was later observed. Although binocular interaction was demonstrated by the interocular transfer of after-effects, the patient never experienced steropsis. He also seemed unable to recognize faces. Dsepite the small visual field, optokinetic nystagmus could be elicited. A notable slowing down of visual analyses was observed in experiments on visual reaction time, on the inversion of the Necker cube, and on binocular rivalry. The complete loss of certain functions like steropsis or face recognition in contrast to a quantitative reduction of other functions like visual acuity or color perception can be discussed in the light of two conceptual models of perceptual processing. One model suggests the representation of different visual functions within one neuronal network, each function represented by a different number of neurons or a different algorithm within the network. The second model suggests a spatial segregation of different visual functions in different cortical areas that receive input from one common structure, presumably the striate cortex.

Aged↗
PubMed1978

[Prosopagnosia and disturbance of color recognition during recovery from cortical blindness].

Neuropsychologic findings during recovery from cortical blindness are described in four right-handed patients (two female, two male) aged 53 to 70 years. The lesions were due to occlusion of both posterior cerebral arteries (Case 1) and vascular spasm following subarachnoidal hemorrhage (Case 3) or angiography (Cases 2 and 4). Complete blindness lasted for 3 months until death in Case 1, 4 weeks in case 2, and 1 to 2 days in Cases 3 and 4. Confusional states and visual hallucinations were pronounced in three cases. Anosognosia (Anton's syndrome) was most pronounced in a patient with occlusion of both posterior cerebral arteries and less obvious in the remaining patients. During the recovery phase, symptoms of right hemisphere involvement were prominent with left-sided hemianopsia and diminished optokinetic nystagmus to the left, prosopagnosia in two cases, and dysmorphopsia with altered physiognomic recognition in one case. Transient disturbances of color recognition occurred in three patients. The observations are discussed with reference to clinical and neuropathologic findings of the literature.

Aged↗
PubMed1992

Absence of blue-yellow color vision loss among workers exposed to toluene or tetrachloroethylene, mostly at levels below occupational exposure limits.

Possible color vision loss was examined with Lanthony's new color test and Ishihara's color vision test in 261 solvent workers and 120 controls (48 men and 72 women). The solvent workers were exposed to either predominantly toluene [46 ppm as geometric mean (GM); 63 men and 111 women], tetrachloroethylene alone (13 ppm; 30 men and 34 women), or a mixture (14 men and 9 women) of tetrachloroethylene (12 ppm) and trichloroethylene (7 ppm). The only instances of color vision loss that were detected in either the exposed workers or the controls were six cases of red-green loss (all in men). These six cases of red-green loss showed an unbiased distribution between the exposed workers and the nonexposed controls.

Adult↗
PubMed1987

Solvent related colour vision loss: an indicator of neural damage?

Previous studies have related colour vision loss to solvent exposure, raising the question as to its use as an indicator of solvent-related neurotoxic alterations. However, colour vision loss can likewise result from ocular damage. In the present study chromatic discrimination capacity and ocular integrity were examined among 23 workers of a paint manufacture plant exposed to solvent mixtures. Using industrial hygiene data, the workers were classified according to their exposure level: moderate (n = 13) and high (n = 10). Colour discrimination capacity was assessed using the Farnsworth-Munsell 100 Hue, a colour arrangement test, providing qualitative and quantitative data. Biomicroscopy, funduscopy and peripheral visual field tests were used to examine ocular integrity. The results showed a significantly higher prevalence (P less than 0.02) of chromatic discrimination loss among the highly exposed workers (80%), as compared to the moderately exposed (23.1%). Ocular examination revealed no apparent major damage, although slight posterior sub-capsular opacification, indicative of incipient cataract, and, diminished foveal reflex were observed among 1/3 of the workers. Lens opacification was related to age and exposure duration, but not to exposure level. Diminished foveal reflex was not related to either age, exposure duration or level. Neither observation was related to chromatic discrimination loss. These findings support the hypothesis that chromatic discrimination impairment, associated with solvent exposure, reflects neural, rather than ocular, damage. The authors propose that tests of acquired colour vision loss be included in field batteries to evaluate neurotoxic effects of solvent exposure.

Adult↗