A Study of Congenital Nystagmus

Ninety cases of congenital idiopathic nystagmus were examined by ophthalmologists and by the author, chiefly electrooculographically. The results of these examinations were:The visual acuity of the better eye was normal or almost normal in largely ⅓ of the cases, and the refractive errors of the better eye were absent or small in ½ of the cases. Squint was present in 16 per cent.The neutral zone for regular pendular eye-movements had an eccentric position in 35 per cent to such a degree that turning of the head on fixation ensued.The nystagmus in darkness, as compared to light, was almost always suppressed when the eyes were closed but presented a quite different pattern when the eyes were open, showing decrease in 33, increase in 7 and no decided or variable changes in 60 per cent.Mephenesin depressed the spontaneous nystagmus in ⅓ of the cases and caused a significant decrease of calorically induced nystagmus.The vestibulo-ocular reactivity was undecided in 10, normal in 46 and absent in 44 per cent of the cases. The audiograms were essentially normal. Vestibulo-ocular areflexia was presumed to be caused by central influence.