DISTURBANCES OF SMALL-FIELD HORIZONTAL AND VERTICAL OPTOKINETIC NYSTAGMUS IN AMBLYOPIA

  • 1 January 1980
    • journal article
    • research article
    • Vol. 19  (6) , 668-683
Abstract
Horizontal and vertical small-field optokinetic nystagmus (OKN) were examined in persons with strabismic or anisometropic amblyopia. Reduced velocity for the slow phase of OKN deriven by temporalward and upward target motion presented monocularly was observed in the amblyopic and nonamblyopic eyes of some subjects. A sensory disturbance of perceived motion sensitivity accounting for the abnormal OKN was investigated. Comparisons between the frequency response for OKN and the contrast sensitivity function for perceived motion revealed that amblyopes with asymmetric OKN had equal sensitivity to nasal and temporal target motion. Contrast thresholds for driving the temporal slope phase of OKN were elevated by over 1 log unit above contrast thresholds for perceived temporal target motion. Contrast thresholds for stimulating nasal movement and driving the nasalward slow phase of OKN were equal. Contrast sensitivity to nasal and temporal target motion was symmetrical at the fovea and parafovea of the amblyopic eye. No sensory anomaly was revealed as the basis for abnormal OKN in amblyopia. Directional asymmetries in OKN were observed in both eyes of persons with congenital strabismus without amblyopia and in the nondeprived eye in monocular congenital cataract. A relationship between directional asymmetries of OKN and the incomplete development of binocular vision apparently exists.