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R. E. CARR, H. RIPPS; Rhodopsin Kinetics and Rod Adaptation in Oguchi's Disease. Invest. Ophthalmol. Vis. Sci. 1967;6(4):426-436.
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The extra-foveal dark adaptation curve of the normal eye is bipartite; the early and late segments representing adaptation of the cone and rod mechanisms, respectively. In Oguchi's disease (one of the congenital forms of night blindness) the cone branch may be extended for nearly two hours, after which time the rod branch appears, and thresholds descend slowly to the normal absolute level. It is usually assumed that this prolonged course of dark adaptation is due to an abnormality involving the synthesis of the rod pigment, rhodopsin. However, by means of fundus reflectometry, we have shown that the concentration of rhodopsin, its photosensitivity, and the rate at which it regenerates after photolysis are entirely normal. This lack of correspondence between visual pigment concentration and visual sensitivity could be demonstrated also by exposing the fully dark-adapted eye to light which bleached less than one per cent of the available rhodopsin. Whereas a normal subject quickly readapted to the dark-adapted level in about seven minutes, thresholds wereraised nearly 3 log units in the case of a subject with Oguchi's disease--and remained there for at least 30 minutes. Studies of the electroretinal responses (ERG and EOG) in this subject indicate that the visual disturbance remits probably from defective neural processes within the retina. In this respect, Oguchi's disease is similar to other forms of congenital stationary nightblindness, although the transient nature of the defect suggests a different physiological basis.
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