[A study of visual function in congenital nystagmus--mechanism of visual improvement after stereotactic superior...

The clinical features of congenital nystagmus (CN) were studied statistically in 106 cases of CN. The point of the nystagmus at which the patients could best see the targets was detected in some patients. The effects of superior colliculectomy on their visual disturbance and the mechanism will be discussed. The study population comprises 106 patients, 79 males and 27 females, aged from one to 64 (mean 19.4 years). Patients with jerky type classified on ENG were found in 53 cases (50%), pendular type in 39 cases (37%), and mixed type in 14 cases (13%). Patients with jerky type showed significantly good visual acuity (mean 0.69 +/- 0.31, p less than 0.005). They showed significant abnormalities during pregnancy and delivery (p less than 0.01) and had a neutral point (p less than 0.01). Patients with pendular type, on the other hand, showed poor visual acuity (mean 0.26 +/- 0.30) and had significant frequency of family history (p less than 0.05), head tremor (p less than 0.01) and strabismus (p less than 0.01). Thirteen cases (12%) had ocular diseases which involved the retina, cornea and optic nerve. Visual function was elaborated on such parameters of ENG as perception, peak variation and plateau time. Perception, which means the ability to detect the dim flashes during the appearance of the nystagmus, was manifested by pushing a button when patients could detect flashes presented at random on the screen. At the turning point from the quick phase to the slow phase, the detection was executed most successfully. It is thought that in CN, a target is usually gazed upon at a point, changing the direction from the quick phase to the slow phase.(ABSTRACT TRUNCATED AT 250 WORDS)