Effect of the distance of optokinetic stimuli from the eyes on certain parameters of the optokinetic nystagmus.
The above effect was studied in 65 subjects with normal vision (mean age 20 years) in investigations in which the following factors were successively changed: distance of optokinetic stimuli from the eyes; this distance and angular velocity of stimuli; distance and frequency of stimuli or finally distance and accommodation level. The angular velocity of the pursuit nystagmus phase was found to be by far the highest and simultaneously the closest to the angular velocity of optokinetic stimuli when the latter are 1.5m from the eyes. With shorter distances, the velocity of the pursuit movements lags steadily behind that of stimulus velocity. This change is conditioned by changes in OKN amplitude since its frequency as a whole does not change. Even though the accommodation level significantly affects the velocity of the pursuit nystagmus phase, the dependence on the distance of optokinetic stimuli from the eyes persists even after atropinization. The interpretation of these findings must take into account sepcifically the demands on accommodation, convergence, and on visual attention which are increased with shorter distances.
D000065:Accommodation, Ocular; D001288:Attention; D005133:Eye Movements; D006801:Humans; D010775:Photic Stimulation