Visual field severity indices demonstrate dose-dependent visual loss from vigabatrin therapy.
OBJECTIVE
The aims of this study were to develop an algorithm to accurately quantify Vigabatrin (VGB)-induced central visual field loss and to investigate the relationship between visual field loss and maximum daily dose, cumulative dose and duration of dose.


METHODS
The sample comprised 31 patients (mean age 37.9 years; SD 14.4 years) diagnosed with epilepsy and exposed to VGB. Each participant underwent standard automated static visual field examination of the central visual field. Central visual field loss was determined using continuous scales quantifying severity in terms of area and depth of defect and additionally by symmetry of defect between the two eyes. A simultaneous multiple regression model was used to explore the relationship between these visual field parameters and the drug predictor variables.


RESULTS
The regression model indicated that maximum VGB dose was the only factor to be significantly correlated with individual eye severity (right eye: p = 0.020; left eye: p = 0.012) and symmetry of visual field defect (p = 0.024).


CONCLUSIONS
Maximum daily dose was the single most reliable indicator of those patients likely to exhibit visual field defects due to VGB. These findings suggest that high maximum dose is more likely to result in visual field defects than high cumulative doses or those of long duration.
Conway
Miriam
M
Department of Optometry and Visual Science, City University, London, UK. miriam.conway.1@city.ac.uk
Cubbidge
Robert P
RP
Hosking
Sarah L
SL
D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D000927:Anticonvulsants / Q000008:administration & dosage / Q000009:adverse effects* / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D004827:Epilepsy / Q000188:drug therapy*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D008452:Maximum Allowable Concentration; D008875:Middle Aged; D012044:Regression Analysis; D012607:Scotoma / Q000139:chemically induced / Q000175:diagnosis; D012720:Severity of Illness Index; D020888:Vigabatrin / Q000008:administration & dosage / Q000009:adverse effects* / Q000627:therapeutic use; D014786:Vision Disorders / Q000139:chemically induced* / Q000175:diagnosis; D058609:Visual Field Tests / Q000295:instrumentation / Q000706:statistics & numerical data; D014794:Visual Fields / Q000187:drug effects* / Q000502:physiology
D000927:Anticonvulsants; D020888:Vigabatrin