Two cases of optic neuritis in which relative afferent pupillary defect and decreased critical flicker fusion frequency could be detected before visual acuity worsened

Abstract

RAPD (relative afferent pupillary defect) for light reflex and decreased CFF (critical flicker fusion frequency) are sensitive indicators of unilateral optic neuritis. Previous studies have shown that light reflex and CFF usually improve more slowly than visual acuity during the recovery period of optic neuritis. However, there are few chances to observe the relationship between visual acuity and light reflex or between visual acuity and CFF during the early onset of optic neuritis. This paper describes two cases of unilateral optic neuritis in which RAPD and decreased CFF could be detected during early onset before visual acuity worsened. The cases show that a dissociation between visual acuity and light reflex or between visual acuity and CFF may also occur during the early onset of optic neuritis, as it can during the recovery or remission period. That is, light reflex and CFF are affected more rapidly and recover more slowly in optic neuritis. Therefore, when patients with normal visual acuity complain of visual symptoms of unknown origin, investigators must keep the possibility of optic neuritis in mind while observing light reflex and measuring both visual acuity and CFF.