Detecting vigabatrin toxicity by imaging of the retinal nerve fiber layer.
OBJECTIVE
To quantify retinal nerve fiber layer thickness (RNFLT) and macular thickness (MT) in patients exhibiting vigabatrin-attributed visual field loss (VAVFL) and to determine the efficacy of these measures as markers of the retinal damage associated with vigabatrin.


METHODS
This was a prospective cross-sectional observational study involving five groups: Group I, 13 patients exhibiting VAVFL; Group II, 8 patients exposed to vigabatrin but with normal fields; Group III, 14 patients receiving carbamazepine monotherapy; Group IV, 20 normal individuals; and Group V, 7 patients receiving sodium valproate monotherapy. At one of two visits, the right eye of each participant underwent two digital imaging modalities: ocular coherence tomography (OCT; StratusOCT; Carl Zeiss Meditec, Dublin, CA) and scanning laser ophthalmoscopy (SLO; Heidelberg Retinal Tomograph; Heidelberg Engineering GmbH, Heidelberg, Germany). At the other visit, participants underwent three-zone, age-corrected suprathreshold perimetry of the whole field and threshold perimetry of the central field (Humphrey Field Analyzer 750; Carl Zeiss Meditec). The order of the visits was randomized.


RESULTS
The group mean RNFLT in Group I was attenuated relative to that of the remaining groups (all P < 0.001). At 100% specificity, based on the 95% confidence limits derived from Group IV, OCT exhibited 100% sensitivity and SLO 77% sensitivity for an attenuated RNFLT in patients with VAVFL. All participants manifested an MT within the normal range derived from Group IV.


CONCLUSIONS
OCT of the RNFL can efficiently identify vigabatrin-induced damage and will be useful for adults and children unable to perform perimetry and when the perimetric outcome is equivocal.
Wild
John M
JM
Cardiff School of Optometry and Vision Sciences, Cardiff University, Cardiff, Wales, United Kingdom. wildjm@cf.ac.uk
Robson
Catherine R
CR
Jones
Adrian L
AL
Cunliffe
Ian A
IA
Smith
Philip E M
PE
D000328:Adult; D000927:Anticonvulsants / Q000009:adverse effects*; D002220:Carbamazepine / Q000627:therapeutic use; D003430:Cross-Sectional Studies; D004827:Epilepsy / Q000188:drug therapy; D005260:Female; D006801:Humans; D008297:Male; D009412:Nerve Fibers / Q000187:drug effects / Q000473:pathology*; D009887:Ophthalmoscopy; D011446:Prospective Studies; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000473:pathology*; D012680:Sensitivity and Specificity; D041623:Tomography, Optical Coherence; D014635:Valproic Acid / Q000627:therapeutic use; D020888:Vigabatrin / Q000009:adverse effects*; D014786:Vision Disorders / Q000139:chemically induced / Q000175:diagnosis*; D058609:Visual Field Tests; D014794:Visual Fields / Q000187:drug effects*
D000927:Anticonvulsants; D002220:Carbamazepine; D014635:Valproic Acid; D020888:Vigabatrin