[Visual evoked potential and relative afferent pupillary defect in patients with unilateral optic neuritis]

The relationships between relative afferent pupillary defect (RAPD) and visual evoked potential (VEP), visual acuity or visual field in 14 patients with idiopathic unilateral optic neuritis, were investigated during the period of recovery from an acute episode. Grading of RAPD into four steps mainly based upon an escape phenomenon in a swinging flashlight test, was used to determine the degree of RAPD. The degree of RAPD significantly correlated with a reduction in VEP amplitude, visual acuity and loss of central visual field, while it did not correlate with delay in VEP latency. These results suggest that RAPD is mainly related to the integrity of central vision, and that grading of RAPD, as well as a comparison of VEP amplitude between the affected and contralateral eyes, is useful for an objective evaluation of visual functions of the affected eyes in patients with unilateral optic neuritis.