Optokinetic nystagmus is the rhythmical scanning of the eyes when primates attempt to stabilize constantly moving visual scenes. If a pattern having distinct vertical features is projected onto a screen and is drifted to the left or to the right, variations of certain parameters associated with optokinetic nystagmus of a subject observing the drifting pattern from the values of those parameters for persons having normal, healthy vision provide an indication of damage to M-type ganglion cells due to the presence of glaucoma in the subject. Such variations occur at an early stage of glaucoma, before other positive indications of the disease are present. Preferably the projected pattern is a coarse sinusoidal grating with vertical striations, which is temporally modulated by a rapid movement or flicker.
Glaucoma testing from observations of optokinetic nystagmus