Since eye pairs are anatomically and pathologically asymmetrical, we attempted to determine whether the transition from ocular hypertension to glaucoma might be typified by lateral differences in either intraocular pressure (IOP), papillary excavation, or visual field. Such lateral differences were sought in a retrospective study of the medical records of 47 patients exhibiting ocular hypertension, of whom 25 remained hypertensives and 22 developed glaucoma during the period considered. Although all visual field indices in the latter group had remained within the normal range, the same side consistently yielded significantly worse results in mean sensitivity, and the absolute value for the lateral difference in these individuals was significantly higher than that found for the patients who did not develop glaucoma. Future glaucoma is manifested when the mean sensitivity remains worse in one eye.