Ocular motility anomalies in developmental misdirection of the optic chiasm.
A 35-year-old normally pigmented man underwent monocular hemifield visual-evoked potential examinations that indicated a lack of normal decussation of nasal paramacular retinogeniculate fibers in the optic chiasm. We studied effects of this anomaly on ocular motility using electro-oculography and the magnetic search-coil technique. The patient exhibited horizontal congenital nystagmus with a predominantly positive exponential waveform. Horizontal smooth pursuit and optokinetic nystagmus were consistently reversed, independent of eye position in the orbit. Vertical tracking was uniformly normal. Horizontal vestibulo-ocular reflexes recorded in the dark during passive rotation exhibited normal gain and phase, whereas rotation recorded in the light reduced gain. Although active head movements reversed horizontal vestibulo-ocular reflexes, vertical vestibulo-ocular reflexes in light and darkness were normal. Our study suggested an association between a lack of normal decussation of retinal fibers in the optic chiasm, and reversed visual tracking and congenital nystagmus.
McCarty
J W
JW
Jules Stein Eye Institute, UCLA 90024-7002.
Demer
J L
JL
Hovis
L A
LA
Nuwer
M R
MR
D000328:Adult; D004585:Electrooculography; D005074:Evoked Potentials, Visual; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009434:Neural Pathways / Q000002:abnormalities; D009759:Nystagmus, Pathologic / Q000151:congenital* / Q000503:physiopathology; D009897:Optic Chiasm / Q000002:abnormalities* / Q000503:physiopathology; D009900:Optic Nerve / Q000002:abnormalities / Q000503:physiopathology; D012438:Saccades