Attenuation of the retinal nerve fibre layer and reduced retinal function assessed by optical coherence tomography and full‐field electroretinography in patients exposed to vigabatrin medication

Abstract

ABSTRACT.Purpose: To investigate the clinical value of assessment of peripapillary retinal nerve fibre layer (RNFL) thickness with OCT in addition to the evaluation of retinal function measured by full-field electroretinography (ff-ERG) in patients with suspected vigabatrin (VGB)-attributed visual field defects. Methods: Visual fields from adult patients in our clinical follow-up program for VGB medication were analysed. Twelve patients with suspected VGB-attributed visual field defects were selected for the study. They were re-examined with computerized kinetic perimetry, ff-ERG and OCT (2D circle scan). Results: Constricted visual fields were found in all patients. Comparative analysis of ff-ERG parameters showed reduced b-wave amplitudes for the isolated and the combined rod and cone responses (p < 0.0001). The a-wave, reflecting photoreceptor activity, was reduced (p = 0.001), as well as the summed amplitude of oscillatory potentials (p = 0.029), corresponding to inner retinal function. OCT measurements demonstrated attenuation of the RNFL in nine of 12 patients, most frequently superiorly and ⁄ or inferiorly. No temporal attenuation was found. Significant positive correlations were found between the total averaged RNFL thickness, superior and inferior RNFL thickness and reduced ff-ERG parameters. Positive correlations were also found between RNFL thickness and isopter areas. Conclusion: OCT measurements can detect attenuation of the RNFL in patients exposed to VGB medication. RNFL thickness correlates with reduced ff-ERG parameters and isopter areas of constricted visual fields, indicating that VGB is retino-toxic on several levels, from photoreceptors to ganglion cells. The study also supports previous studies, suggesting that OCT measurement of the RNFL thickness may be of clinical value in monitoring patients on vigabatrin therapy.

Vigabatrin retinal toxicity in children with infantile spasms

“…VGB toxicity has a complex pathophysiology occurring as a result of accumulation of VGB in the retina and/or elevated levels of retinal GABA. In humans, changes to the electrooculogram, 32 cone and rod system, 32 , 33 and disruption on retinal nerve fiber layer 34 occur with VGB treatment. A change in the electrooculogram is probably an early, possibly reversible retinal defect attributed to VGB, resulting from disruption at the retinal pigment epithelium/photoreceptors border.…”

Does vigabatrin treatment for infantile spasms cause visual field defects? An international multicentre study

“…Examination of the retinal nerve fibre layer using optical coherence tomography has recently been introduced as an alternative method for follow‐up of vigabatrin toxicity . However, optical coherence tomography also requires the cooperation of the patient.…”

“…8 Examination of the retinal nerve fibre layer using optical coherence tomography has recently been introduced as an alternative method for follow-up of vigabatrin toxicity. 9 However, optical coherence tomography also requires the cooperation of the patient. According to the guidelines, patients who are not subject to scheduled ophthalmic testing should not continue with vigabatrin treatment.…”

Vigabatrin Retinal Toxicity First Detected with Electroretinographic Changes: A Case Report

“…It has been suggested that OCT be used to screen for VGB induced retinal toxicity because this test can show thinning of the RNFL which is associated with visual field loss [12]. Notably, here, the patient's OCT was normal until the acute presentation of decreased visual acuity (Figure 1, 2014.03).…”