Defective colour vision in diabetic retinopathy before and after laser photocoagulation.
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Two families from northern Sweden with a total of 8 patients with typical symptoms of congenital achromatopsia with amblyopia were studied. In one of the families 4 affected children (3 brothers and 1 sister) also showed pallor of the optic discs and marked astigmatism. The transmission of the disease was consistent with an autosomal recessive inheritance in both families. The study confirmed that complete and incomplete achromatopsia might be different expressions of the same gene. Six out or 13 near relatives of the achromatic patients showed minor colour vision defects, suggesting a tendency towards heterozygotic manifestation of the gene.
Pathology of the visual system can alter perception in the central and peripheral visual field. Pseudoisochromatic plates and pigment panel tests can be used to study macular color vision. Perimetric techniques using color targets extends testing to the peripheral field. This facilitates detection of early, sometimes subtle defects that are missed with conventional white-target perimetry. The stimulus conditions and methods of color perimetry are reviewed in this paper, particularly recent methodological advancements which offer a potential for increased sensitivity in detection of pathology.
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Several tests are available for assessing colour vision but they can be expensive, complicated or too time consuming to perform. We have produced a new plate test based on pseudoisochromatic principles. The test, using an error score, examines both the red-green and blue-yellow axes, with four levels of difficulty for each axis. Results from a pilot study show that error scores from congenital red-green blind subjects are significantly higher than those of age-matched controls (p < 0.01) only when using the red-green plates and not the blue-yellow plates. In optic neuritis patients, error scores using both the red-green and blue-yellow plates were significantly higher than those of controls throughout the 6 month follow-up. The test, including scoring, takes 6 minutes to complete. These preliminary results suggest that the new test is effective for screening congenital red-green blindness and monitoring colour vision defects in acquired diseases such as optic neuritis.
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The influence of congenital colour defects on a clinical computer test for equiluminous colour discrimination is studied. Differences in relative spectral sensitivity and changes in colour contrast discrimination are two distinct manifestations of the abnormal genes responsible for congenital red-green defects. The very simple and rapid method of the heterochromatic flicker brightness test acts like an anomaloscope and can be used to distinguish protan and deuteran defectives. The depth of the congenital colour defect can be quantified by the colour contrast threshold measured in equiluminous conditions along a single red-green axis identical for all types of red-green colour defectives. Colour contrast thresholds in tritan colour axes are not influenced by congenital red-green defects and therefore they are of extreme clinical interest to detect and quantify acquired colour defects, even in the presence of a previously unknown congenital red-green defect.
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The 1974 and 1975 aircraft accident experiences of civilian pilots with eight selected static physical defects have been examined and reorted previously. Three categories--blindness or absence of either eye, deficient color vision with a waiver, and deficient distant vision--had significantly more accidents than were expected on the basis of observed-to-expected ratios. In 1975, accident rates were calculated. The rates for air men with blindness or absence of an eye were still found to be significantly higher. Observed-to-expected ratios for 1976 were 1.91 for deficient color vision with a waiver, 1.28 for contact lens users, 1.37 for blindness or absence of either eye, and 1.62 for deficient distant vision. The accident rates per 100,000 h of cumulative and last 6 months' flying experience were significantly greater for contact lens users and monocular pilots than for the active airman population. The other groups had no consistently significant differences.
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