MONOCULAR OPTOKINETIC NYSTAGMUS IN HUMANS WITH AGE-RELATED MACULOPATHY

Aim--To investigate full field monocular optokinetic nystagmus (OKN) i n patients with age-related maculopathy (ARM) and relative central sco toma. Methods--Six patients aged 59-88 years with bilateral ARM and an aged-matched control group of six patients aged 54-83 years were exam ined. Visual fields were assessed with a Humphrey field analyser using the threshold 30-1 routine. Monocular full field horizontal optokinet ic stimuli were presented on a hemicylindrical screen subtending 172 d egrees horizontally and 50 degrees vertically. The stimulus was a proj ected random dot pattern and three stimulus velocities were used, 30, 50, and 70 degrees/s in both nasalward and temporalward directions. Ea ch trial lasted between 30 and 40 seconds and eye movements were monit ored using infrared oculography. Results--The ARM patients had relativ e central scotomas with an average depth of 10 dB. Neither the ARM nor the age-matched groups displayed any directional preponderance or a b uildup of the slow phase eye velocity with time. No statistically sign ificant difference in the gain was found between the two groups (p>0.0 5). Conclusions--Marked central field loss in ARM does not significant ly impair OKN gain. This supports the view that complete central retin al integrity is by no means essential and that the peripheral retina p rovides an important input to the generation of OKN.