Separating the retinal electrophysiologic effects of vigabatrin: treatment versus field loss.
OBJECTIVE
To separate the retinal electrophysiologic markers associated with vigabatrin-attributed visual field loss (VGB-VFL) from those associated with current vigabatrin therapy.


METHODS
A nonrandomly selected cohort of 8 previous and 18 current vigabatrin users and a reference cohort of 8 never vigabatrin-treated patients with epilepsy receiving other antiepilepsy drugs (AED) underwent electro-oculography (EOG), electroretinography (ERG), and automated static threshold perimetry. A cohort of 22 normal subjects underwent ERG. The validity of the retinal electrophysiologic variables to detect the presence and severity of VGB-VFL was assessed using receiver operator characteristic curves.


RESULTS
Of 26 patients exposed to vigabatrin, 18 exhibited VGB-VFL. No patients receiving alternative AED showed this type of visual field abnormality. The presence and severity of VGB-VFL was significantly associated with the latency (implicit time) and amplitude of the ERG cone function. The amplitude of the cone flicker response was the strongest predictor of VGB-VFL and revealed a sensitivity of 100% at a specificity of 75%. The EOG, the photopic and scotopic ERG, and the latency of the ERG second oscillatory potential (OP2) were not significantly related to the presence of VGB-VFL. Vigabatrin therapy was significantly associated with the photopic amplitude, the scotopic a-wave latency, and the latency of OP2.


CONCLUSIONS
In patients who cannot perform reliable perimetry, the cone-specific ERG flicker amplitude provides the best screening method for detecting VGB-VFL.
Neurosciences Research Institute, School of Life and Health Sciences, Aston University, Birmingham, UK. g.f.a.harding@aston.ac.uk
G F
GF
Harding
J M
JM
Wild
K A
KA
Robertson
S
S
Rietbrock
C
C
Martinez
D000328:Adult; D000927:Anticonvulsants / Q000009:adverse effects*; D019540:Area Under Curve; D004585:Electrooculography; D004596:Electroretinography; D004827:Epilepsy / Q000188:drug therapy*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012164:Retinal Diseases / Q000139:chemically induced* / Q000175:diagnosis*; D012680:Sensitivity and Specificity; D020888:Vigabatrin / Q000009:adverse effects*; D014794:Visual Fields / Q000187:drug effects
D000927:Anticonvulsants; D020888:Vigabatrin