Fast Transient Visual Evoked Potential Correlates With Functional and Structural Damage in Glaucoma

Abstract

Purpose: : Glaucoma diagnosis and management is based on the assessment of optic nerve structure and function. The conventional pattern-reversal visual evoked potential (VEP) technique has been used as an objective method of evaluating the visual pathway. We investigated the correlation between structural and functional damage in patients with asymmetric glaucoma using a fast transient VEP (ftVEP) device.

Methods: : Twenty-three subjects with bilateral glaucoma (glaucomatous optic neuropathy + visual field defects) and visual acuity ≥ 20/25 underwent optical coherence tomography (Stratus OCT) for macular thickness measurement, scanning laser polarimetry with variable corneal compensation (GDx-VCC) for RNFL measurement and ftVEP (Diopsys, Inc., Pine Brook, NJ; 10 and 85% Michelson of contrast, acquisition time of 20s) in both eyes within 2 months. Asymmetric glaucoma was defined as a difference in MD of at least 3 dB (SITA Standard 24-2). The correlation between structural test results (OCT and GDX) and the ftVEP parameters, P100 latency and delta amplitude (N75-P100) was assessed.

Results: : Mean age was 61.5 ± 16 years. There was a significant difference in MD values between the more and less affected eyes (-13.7 ± 6.7 vs -2.8 ± 2 dB, p0.05).

Conclusions: : In cases of asymmetric glaucoma, ftVEP 10% and 85% contrast correlated with VF MD. In eyes with moderate VF loss, ftVEP 85% contrast correlated better with macular thickness than parapapillary RNFL thickness. The delayed latency observed with the 10% contrast requires further investigation.

Keywords: visual fields • optic nerve • nerve fiber layer