Characteristics of hyperacuity sensitivity in normal and cyclovertical deviation subjects.

PURPOSE To compare the sensitivity of hyperacuity of patients with cyclovertical deviation with that of subjects with normal vision. METHODS The sensitivity of hyperacuity was measured in 42 volunteers with normal vision and in 12 patients with cyclovertical deviation, using a newly developed computerized device that randomly presents two opposing targets at vertical or at horizontal directions on the cathode ray tube display. RESULTS In subjects with normal vision, higher sensitivity was obtained when the targets were aligned in either a vertical or a horizontal direction. These highly sensitive ranges were defined as "the neutral zone of hyperacuity." An anisotropy of the sensitivity of hyperacuity was observed in these subjects, ie, better sensitivity was obtained when the displacement was away from the neutral zone, whereas worse sensitivity was obtained when the displacement was close to the neutral zones. In the patients with cyclovertical deviation, the sensitivity of hyperacuity was low around the neutral zones, which may confirm the dysfunction of the central nervous system. CONCLUSION This analytical method may be useful to investigate the pathophysiology of patients with cyclovertical deviations.