Evaluating the clinical applications of visual evoked potentials in patients presenting with visual dysfunctions - A retrospective study

Abstract

Background:The clinical applicability of visual evoked potential (VEP) tests has been progressively extending in neuro-ophthalmological workups. The role in monitoring and follow-ups are emerging as even more useful applications. Aims and Objectives: The present study aimed to assess the clinical role of pattern-reversal VEP (PRVEPs) in visual disorders with presumptive optic nerve involvement. Materials and Methods: PRVEP records of 58 patients with unilateral/bilateral visual loss in a study period of 1½ year were retrospectively analyzed. P100 latencies and N75-P100 amplitudes were compared with those of 60 age and sex-matched controls. Variations beyond three standard deviations were applied to define significant abnormalities. PRVEP records obtained by follow-up in some conditions were also assessed. Results: Traumatic optic neuropathy (32.76%) was the most common condition confronted, with major PRVEP finding as absent waveforms/reduced amplitudes. Monitoring of VEP records revealed improvement in 50% of patients on corticosteroid therapy. Functional visual disorders constituted 27.6% with 93.75% of subjects confirmed by PRVEP. Ethambutol-induced toxic optic neuropathy (20.69%) was associated with significant P100 delay bilaterally, in the majority. Out of which, 50% showed improved PRVEP records after 1 month of cessation of drug. Multiple sclerosis and optic neuritis though rarer conditions (3.44% and 6.89%, respectively) exhibited characteristic electrophysiological findings which helped confirming the diagnosis. Diabetic optic neuropathy (3.4%) and some very rare conditions also constituted the referrals. Conclusion: VEPs provides sensitive adjuncts to diagnosis in various visual disorders and contributes as important monitoring tools for objectively assessing the recovery and ophthalmological status.