Disjunctive optokinetic nystagmus in a naturally esotropic macaque monkey:Interaction between nasotemporal asymmetries of versional eye movement andconvergence
C. Yildirim et L. Tychsen, Disjunctive optokinetic nystagmus in a naturally esotropic macaque monkey:Interaction between nasotemporal asymmetries of versional eye movement andconvergence, OPHTHAL RES, 32(4), 2000, pp. 172-180
Objective: To assess the interaction between versional and vergence eye mov
ements in normal and strabismic monkeys, Methods: Horizontal optokinetic ny
stagmus (OKN) and vergence were measured using the magnetic scleral search
coil technique in a normal adult monkey and a strabismic monkey who had nat
urally occurring early-onset esotropia. Mean eye velocity and vergence angl
es were calculated during the slow phases of OKN, Results: The strabismic m
onkey had a nasotemporal asymmetry of OKN favoring nasally directed motion
in each eye. During monocular optokinetic stimulation, mean eye velocities
were substantially greater for the adducting as compared to the abducting e
ye. The velocity of the abducting eye was between 55 and 80% of the velocit
y of the adducting eye (p < 0.01). As a consequence of the disjunctive move
ments, the eyes converged an average of 4 +/- 2.8 degrees during OKN, Sacca
dic analysis documented normal lateral rectus function in each eye. Neither
an OKN asymmetry nor disjunctive OKN was observed in the normal monkey. Co
nclusion: Disjunctive OKN in the esotropic monkey suggests that the cerebra
l maldevelopment responsible for nasally biased OKN also contributes to nas
al biases in vergence pathways. Copyright (C) 2000 S. Karger AG, Basel.