On the variations of the time constant of the slow-phase eye movements produced by surgical therapy of congenital nystagmus: a preliminary report.

Quantitative analyses of the effect of nystagmus surgery have been based previously on the pre- and postoperative comparison of the nystagmus intensity at various gaze angles. On the other hand, a recent hypothetical model of the defective oculomotor system producing congenital nystagmus emphasizes that the time constant of the (increasing velocity) slow-phase eye movements should represent a useful parameter in the quantification of the surgical effects, since it is related to the potential good visual acuity of the patients in the presence of nystagmic cycles with extended foveation. By computer analysis of the pre- and postoperative electro-oculographic recordings from 5 patients with congenital nystagmus we show experimentally that the above theoretical indication is a valid tool in the assessment of the effects of classic nystagmus surgery.