Electrophysiologic evidence for normal optic nerve fiber projections in normally pigmented squinters

The Siamese cat, a type of albino, has a visual pathway anomaly in which too many optic nerve fibers cross at the optic chiasm, and also frequently has strabismus. The correlation of strabismus with this defect suggests that a similar pathway defect without pigmentation anomalies, may be the cause of much human strabismus. Creel, Witkop, and King have used evoked potential methods to show that such a pathway defect likely occurs in the human albino. While unpublished control experiments verified their results on human albinos, no such defect has been found in the normally-pigmented human squinter. It is concluded that the visual pathway anomaly is limited to albinism and is not a likely cause of most human strabismus.