Retinal nerve fiber layer thickness in vigabatrin-exposed patients.
OBJECTIVE
Vigabatrin-associated visual field loss (VAVFL) occurs in 25 to 50% of exposed patients and is routinely monitored using perimetry, which has inherent limitations. Using optical coherence tomography (OCT), retinal nerve fiber layer (RNFL) thinning has been described in a small number of vigabatrin-exposed patients. We explored the relationship between RNFL thickness and visual field size, to determine whether OCT is a suitable tool to use in patients exposed to vigabatrin.


METHODS
Two hundred one vigabatrin-exposed subjects with epilepsy, divided into 2 groups, and 90 healthy controls participated. Visual fields were obtained using Goldmann kinetic perimetry and quantified using mean radial degrees (MRD). RNFL imaging was performed using either spectral-domain (Group 1) or time-domain (Group 2) OCT.


RESULTS
Thirty-nine of 201 (19.4%) patients were unable to perform perimetry. Thirteen (6.5%) patients were unable to perform OCT. A total of 51.6% of patients showed VAVFL. Average RNFL thickness was significantly thinner in patients (77.9 μm) compared to healthy controls (93.6 μm) (p < 0.001). There was a strong correlation between MRD and average RNFL thickness for Group 1 (r = 0.768, p < 0.001) and Group 2 (r = 0.814, p < 0.001). OCT RNFL imaging showed high repeatability.


CONCLUSIONS
OCT provides a useful tool to assess people exposed to vigabatrin, and can provide an accurate estimate of the extent of visual field loss in the absence of a reliable direct measure of the visual field. The strong linear relationship found between RNFL thickness and visual field size provides some evidence that irreversible VAVFL may be related to loss of retinal ganglion cell axons.
Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, United Kingdom.
Lisa M
LM
Clayton
Marita
M
Dévilé
Trusjen
T
Punte
Constantinos
C
Kallis
Gerrit-Jan
GJ
de Haan
Josemir W
JW
Sander
James
J
Acheson
Sanjay M
SM
Sisodiya
D000328:Adult; D000927:Anticonvulsants / Q000009:adverse effects*; D004827:Epilepsy / Q000188:drug therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000187:drug effects* / Q000473:pathology*; D015203:Reproducibility of Results; D012160:Retina / Q000187:drug effects / Q000473:pathology*; D013223:Statistics as Topic; D013997:Time Factors; D041623:Tomography, Optical Coherence / Q000379:methods; D020888:Vigabatrin / Q000009:adverse effects*; D058609:Visual Field Tests / Q000379:methods; D014794:Visual Fields / Q000187:drug effects
D000927:Anticonvulsants; D020888:Vigabatrin