Visual evoked potential (VEP) delays in tilted and/or oblique entrance of the optic nerve head

Abstract

Although VEP delays to pattern stimulation were once considered to be a specific finding in demyelinating optic neuropathy, such delays have more recently been reported in non-demyelinating optic neuropathy and in both wet and dry maculopathies. One major group of conditions not well documented in the clinical VEP literature is congenital anomalies of the optic nerve. The authors evaluated ten consecutive patients with the congenital optic nerve anomaly consisting of tilted and/or oblique entrance of the optic nerve in one or both eyes. The visual acuity ranged from 20/20-20/400. No patient had any symptom or clinical evidence of demyelinating disease and the VA was stable in each case. VEPs were recorded to pattern stimuli of 14,28, and 56 minute of arc checks reversing at 1.88 Hz and 7.5 Hz at 76% contrast and mean luminance of 25 cd/m². The VEPs were delayed in 60%-70% of eyes tested depending upon the specific stimulus parameters utilized. In addition, VEPs were reduced and delayed in some patients with 20/20 VA. VEP latency could not be predicted based upon VA, degree of tilt or oblique entrance or presence of visual field anomalies. The authors conclude that delayed VEPs are present in the majority of eyes with tilted/oblique entrance of the optic nerve.

Key Words:

• visual evoked potential
• VEP delay
• tilted disc
• oblique entrance of the optic nerve head
• congenital optic nerve head anomaly