The effects of vigabatrin on electrophysiology and visual fields in epileptics: a controlled study with a discussion of possible mechanisms.
OBJECTIVE
To compare the visual electrophysiology and visual fields of patients taking vigabatrin to those of a control group of epileptics on other anti-epileptic drugs (AEDs).


METHODS
Fourteen epileptics treated with vigabatrin and 10 control patients treated with other AEDs underwent ERG and EOG. Goldmann visual fields were performed and analysed using standard software to measure areas contained within I4e isopters.


RESULTS
The cone and rod b-waves of the ERG, the oscillatory potential amplitudes and Arden indices were reduced in vigabatrin-treated subjects and the oscillatory potentials delayed. The Arden indices were reduced due to an increased dark trough. The areas contained within the I4e isopter of vigabatrin treated subjects were reduced compared to the control group and these areas correlated well with oscillatory potential amplitudes and b-wave amplitudes in the vigabatrin group only.


CONCLUSIONS
The use of vigabatrin is associated with a reduction of the ERG cone b-wave amplitude and oscillatory potentials which correlates with visual field loss. The Arden ratio is reduced in subjects taking vigabatrin but may recover after cessation. However, visual loss may persist in the presence of a recovered EOG. These findings suggest further effects of the drug than those mediated by GABA receptors, and support the contention that the cause of the field loss may be at least in part due to retinal effects. Possible mechanisms are discussed.
Comaish
I F
IF
Department of Ophthalmology, Queen's Medical Centre, Nottingham, UK. comaish@doctors.org.uk
Gorman
C
C
Brimlow
G M
GM
Barber
C
C
Orr
G M
GM
Galloway
N R
NR
D000328:Adult; D000927:Anticonvulsants / Q000009:adverse effects* / Q000627:therapeutic use; D035061:Control Groups; D004585:Electrooculography; D004596:Electroretinography; D004827:Epilepsy / Q000188:drug therapy* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012160:Retina / Q000187:drug effects* / Q000503:physiopathology*; D017949:Retinal Cone Photoreceptor Cells / Q000187:drug effects / Q000503:physiopathology; D017948:Retinal Rod Photoreceptor Cells / Q000187:drug effects / Q000503:physiopathology; D020888:Vigabatrin / Q000009:adverse effects* / Q000627:therapeutic use; D014794:Visual Fields / Q000187:drug effects*
D000927:Anticonvulsants; D020888:Vigabatrin