Determinations of the horopter in esotropia.

Eight binocularly abnormal subjects, including 5 esotropes, made successive horopter settings on several different days. The individual data frequently showed irregularities that were not always repeatable, most likely due to vergence instabilities. However, the mean standard error of the means of several replications produced a more nearly smooth horopter locus. Some of the subjects showed a tendency to make settings to the right of the straight ahead that were displaced proximally (eso disparity). It would appear that repeated measures can be useful in neutralizing the effect of extraneous changes in eye position, provided that these are not too large. The strabismus horopter is most likely very similar in shape and location to that found in the normal.