Patten Visual Evoked Potential (P-VEP) in Adult Monocular Amblyopia

Abstract

Purpose: : To investigate the clinical guideline of pattern visual evoked potential (P-VEP) parameters as the diagnostic criteria for adult monocular amblyopia

Methods: : From Jan 2000 to May 2008, medical charts of patients who visited for medical certificates for the military service were reviewed. Any suspicious malingering patients or bilateral amblyopic patients were excluded. Only patients who has definite causes of amblyopia or whose amblyopia has been confirmed on the childhood medical record were included in the study group. Normal subjects who have best-corrected visual acuity more than 20/20 were selected as the control group. The P₁₀₀ latency and amplitude were compared between the amblyopic eye and the normal control group. The P₁₀₀ latency and amplitude ratios were calculated from both eyes and were compared between the amblyopic group and the normal control group.

Results: : Eighty-two charts of patients were reviewed. Sixty-seven patients were included in this study. Forty-seven patients were monocular amblyopic group and 20 patients were normal control group. Of the 47 monocular amblyopic patients, 32 had anisometropic amblyopia, 4 had strabismic, 3 had visual deprivation, and 8 had idopathic amblyopia. The P₁₀₀ latency of monocular amblyopic eye was 118.69±27.02msec, which was significantly delayed than that of normal subjects, 103.62±5.45msec. The P₁₀₀ amplitude of monocular amblyopic eye was 5.89±3.23µV, which was significantly decreased than that of normal subjects, 8.84±4.57µV. The P₁₀₀ latency ratio of monocular amblyopic group was 1.18±0.32, which was significantly higher than that of normal subjects, 1.03±0.02. The P₁₀₀ amplitude ratio of monocular amblyopic group was 0.65±0.36, which was significantly lower than that of normal subjects, 0.77±0.15. All patients with P₁₀₀ latency ratio more than 1.10 had monocular amblyopia. All patients with P₁₀₀ amplitude ratio less than 0.47 had monocular amblyopia. 21(44.7%) out of 47 monocular amblyopic patients showed P₁₀₀ latency ratio within 2 SD of the normal control group. 30(63.8%) out of 47 monocular amblyopic patients showed P₁₀₀ amplitude ratio within 2 SD of the normal control group.

Conclusions: : The P₁₀₀ latency ratio more than 1.10 or the P₁₀₀ amplitude ratio less than 0.47 can be used as the diagnostic criteria of adult monocular amblyopia. Although some patients with monocular amblyopia showed normal P-VEP parameters, P-VEP could be employed usefully as a diagnostic tool for adult monocular amblyopia. The clinical correlation is mandatory to diagnose adult monocular amblyopia.

Keywords: amblyopia • electrophysiology: clinical • visual acuity