[Deuteranopia and deuteranomaly].
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The study describes neuro-ophthalmologic findings in two patients with brain infarction who developed homonymous hemiachromatopsia with resolution to pure homonymous achromatopsia in an upper quadrant. All other visual parameters were normal; only color perimetry was capable of demonstrating the visual disorder. The results are presented with special emphasis on the macular region. Computed tomography studies and magnetic resonance imaging revealed lesions in the caudal and medial occipitotemporal gyri as well as in adjacent cortical regions. The lesions were secondary to disordered circulation in a proximal occipitotemporal branch of the posterior cerebral artery. The anatomical findings and functional relations of color vision in man are discussed in the light of animal findings.
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Pathologic scotopization, an important symptom of retinal disease, can be studied by means of the Nagel II anomaloscope. This method is called the micro-screw method. The micro-screw method was performed in 14 congenital and 13 acquired colour vision defective individuals. The method proves to be useful in detecting symptoms of rod intrusion in colour vision under photopic conditions.
The Nagel-II micro-screw method uses eleven colour equations between 620 and 560 nm. The luminance settings are given and are based on the data of colour normal individuals. In the shortened version, intended to detect pathologic scotopization, it is ascertained at which position of the micro-screw the patient's colour adjustments drop beneath the level of 60 scale Units. A total of 64 patients was examined. 29 congenital colour defectives and 35 acquired colour defectives. With the shortened micro-screw method the patients can be divided into four groups: (1) a group without pathologic scotopization, which includes congenital protan defectives: (2) a group in which pathologic scotopization starts; (3) a group with evident pathologic scotopization, due to Stargardt's disease and other cone dystrophies; and (4) a group with complete pathologic scotopization, which includes the congenital achromats and the end-stages of the cone dystrophies.
The minimum requirements for a reliable study of (acquired) defects of colour vision have been formulated by Verriest. Taking these minimum requirements as a guide, about 200 patients were selected. For the differential diagnosis of disorders of the retina and the optic nerve the determination of the neutral zone and examination with the anomaloscope are important. This is true for both red-green and blue-yellow defects.
Certain professions necessitate correct recognition of colour in their practice. Early defection of coloured vision abnormalities and professional orientation are therefore very important, especially as it is known that 8 % of the population presents a congenital dyschromatopsy of which one fourth (about 2 %) are serious dyschromatopsies which will prevent the practice of a certain number of professions.
We studied color vision in 32 patients with autosomal recessive achromatopsia. Color matching revealed complete achromatopsia (rod monochromasy) in ten patients (Group I) and incomplete achromatopsia in the remaining twenty-two patients. Amongst the incomplete achromats, were three groups distinguishable by their color matching. Patients in Group II were dichromats; their color matches were mediated by rods and MWS (middle-wavelength sensitive) cones. Patients in Groups III and IV were trichromats. Color matches of patients in Group III were mediated by rods, LWS (long-wavelength sensitive) cones and MWS cones. Group III patients showed no evidence of SWS (short-wavelength sensitive) cones. Color matches of patients in Group IV were mediated by rods, LWS cones and SWS cones; color matching did not reveal MWS cones.
The significant advances in our understanding of color vision has been due to the convergence of information from behavioral and molecular genetic analyses. The molecular biology of the visual pigments; molecular genetic basis of variation in normal and abnormal color vision, and regulation of the genes at the LWS-MWS pigment gene locus are discussed.
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By means of a visual tristimulus colorimeter according to Guild-Bechstein, the following items were determined for a male deuteranopic observer on a foveal, i.e. 2 degrees diameter visual field: (1) the deuteranopic missing color, by means of the perceptual criterion "indistinguishably equal", (2) the neutral zone, by means of the perceptual criterion "neither blue nor yellow," (3) the alychne trace, by means of the perceptual criterion "heterochromatically equally bright." The evaluation in the chromaticity chart resulted in two straight lines forming a dichromatic pencil, the deuteranopic missing color providing the carrier point (vertex). These two straight lines represent the referential chromaticities of a deuteranopic opponent color system.
BACKGROUND: Functional visual deficits can occur in patients with diabetes mellitus who show no visible morphological alterations in the retina. In this study we examined the colour vision of diabetic patients using metameric matches. Patients with and without retinopathy, as well as those who had been treated with laser photocoagulation, were examined to ascertain how the functional alterations in the diabetic eye alter with disease status. METHODS: Rayleigh (red-green) and Moreland (blue-green) metameric matches were determined in a total of 51 diabetic patients (24 patients with no retinopathy, 12 patients with background retinopathy and 15 patients who had undergone laser therapy). Their results are compared to those of a control group of 25 subjects with normal colour vision. RESULTS: A deficit in blue-green colour discrimination found in patients without retinopathy becomes worse with the appearance of vascular alterations in the retina. There is also a significant shift towards green in the Rayleigh match midpoint and towards blue in the Moreland match midpoint, which is at least in part explicable by alterations in lens opacity. Patients who have undergone laser therapy show, on average, better colour discrimination than those with retinopathy, but there is a large variation in their results. CONCLUSION: The alterations in the colour vision of diabetics indicate that at least the early functional changes are occurring at an inner retinal location. Lens opacity changes also play a large role as the age of the patients increases.
BACKGROUND: Surgery for macular gliosis and macular holes has become increasingly successful with regard to anatomical outcome. Assessment of the damage to the receptors by these processes is still difficult, but is important in predicting functional outcome. METHODS: Examination with the Nagel II or the Neitz OT anomaloscope was performed in 36 patients with macular gliosis, 23 patients with full-thickness macular holes and 47 patients with central serous choroidopathy. The anomaloscope matches were expressed as the quotient of anomaly. RESULTS: In macular gliosis the mid-matching point is usually 1.0; there is no pseudoprotanomaly. In macular holes the mid-matching point is 1.0 when visual acuity is 0.3 or greater; in eyes with lower visual acuity there may be signs of diminished red sensitivity, but anomaloscope examination becomes difficult. In central serous choroidopathy the mid-matching point is shifted towards red, and pseudoprotanomaly is present, even when visual acuity is normal. CONCLUSIONS: Diseases of the inner retina, in early stages, do not alter colour vision substantially, whereas diseases of the outer retina give rise to early colour vision deficiency. In macular gliosis and macular holes, anomaloscope examination enables estimation of macular receptor misalignment.
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