Retinal nerve fibre layer attenuation: clinical indicator for vigabatrin toxicity

Abstract

. Purpose: To investigate whether persistent visual field defects among patients exposed once to the antiepileptic drug vigabatrin (VGB) were associated with peripapillary retinal nerve fibre layer thickness (RNFLT) attenuation. Methods: Nine individuals with partial epilepsy and VGB‐attributed visual field loss (group 1; 18 eyes) and seven age‐ and gender‐matched individuals with epilepsy and no previous VGB exposure (group 2; 14 eyes) were included in the study. Full‐field 120 point screening perimetry out to 60 degrees from central fixation using the Humphrey Field Analyzer was performed. RNFLT was quantified by optical coherence tomography (OCT) using Fast RNFLT protocol, Stratus OCT (3.0) after pupillary dilation. The results from the right eye are presented in this article. Results: Among the patients with VGB‐attributed visual field loss, five patients had only peripheral field defect (group 1a) and the remaining four had advanced field defects both in the periphery and within 30° from central fixation (group 1b). None of the patients in the control group had manifest visual field loss. The mean RNFLT among the patients with VGB‐attributed visual field loss was significantly attenuated compared to the controls [mean total RNFLT: group 1: 75.6 ± 12.7 μm, group 2: 103.5 ± 9.7 μm, mean difference 27.9 μm, (CI 15.9–39.9; p < 0.001)]. RNFLT values classified as borderline according to normative database (Stratus OCT) occurred more frequently among individuals with VGB‐attributed visual field loss than in controls (frequency in group 1: 6/9; group 2: 0/7, p = 0.011). The nasal, superior and inferior quadrants of RNFLT in individuals with VGB‐attributed visual field loss were significantly attenuated, while no difference was detected in temporal quadrants compared to controls. Both individuals with peripheral and those with advanced visual field losses in the VGB group had attenuated mean total RNFLT compared to controls (p = 0.006, p = 0.002, respectively). Occurrence of borderline classification of total RNFLT ≤5th percentile was more frequent among individuals with advanced visual field loss than among controls (p = 0.048). Conclusion: Persistent visual field loss attributed to VGB is associated with reduced peripapillary RNFLT and was detected both among patients with advanced and among patients with only peripheral visual field defects. Measurements of RNFLT with OCT might be considered as a diagnostic supplement in the follow‐up of patients exposed to vigabatrin.

Optical coherence tomography parameters in patients with photosensitive juvenile myoclonic epilepsy

“…In patients with epilepsy, OCT parameters have been investigated only in a few studies. Most of these studies have related the vigabatrin-exposed epileptic patients, and the relationship between RNFL thickness and visual field loss size has been found [21][22][23].…”

Relationship between the area of isopters and Vigabatrin dosage during two years of observation

“…Moreover, structural measures (particularly ocular coherence tomography - OCT) might also be obtained in these patients instead of VF testing, as Wild [20] and other authors [21] found attenuation of peripapillary RNFL in patients exhibiting constriction of the VF.…”

“…Most of the studies dealing with VGB-attributed VF loss were retrospective, cross-sectional and analyzed the VF results in patients examined first after having started VGB therapy [8,16,21]. The advantage of our study is that it was prospective, performed using standardized method by the same examiner for five times during 2-years period.…”

Vigabatrin-associated retinal damage - potential biochemical mechanisms

“…A decreased Arden ratio indicates dysfunction of the integrity of the photoreceptor–retinal pigment epithelium interface. Additionally, evidence from optical coherence tomography (OCT) demonstrates VGB‐treated patients have thinning of the retinal nerve fiber layer, which was found to be associated with visual field loss . OCT is a non‐invasive technique that allows for objective and quantifiable cross‐sectional imaging of the retina.…”