Abstract
Purpose: :
Vigabatrin is an antiepileptic drug that, nowadays, is used mainly for treatment of infantile spasms in children. It can also be used as add-on therapy in drug-resistant seizures in adults. Vigabatrin is known to cause visual field defects and full-field electroretinography (ff-ERG) changes in 30-60% of adult patients. In children and mentally disabled patients, the adverse effects of the drug can be difficult to identify, since these patients do not easily cooperate in visual field testing and they usually need anesthesia for registration of ff-electroretinograms. The purpose of this study was to evaluate the value of measurement of the retinal nerve fibre layer (RNFL) thickness with optical coherence tomography (OCT) and registration of multifocal visual evoked potentials (mVEPs) in the follow-up of patients on vigabatrin.
Methods: :
12 adult patients, who had previously, during our ordinary follow-up program for vigabatrin medication, presented with visual field defects, were re-examined using computerised kinetic perimetry, ff-ERG, OCT (2D circle scan, measuring the thickess of the RNFL) and mVEP.
Results: :
Visual fields were constricted in all patients, compared to controls. Ff-ERG amplitudes were reduced, including the isolated rod responses, the combined rod-cone responses, 30 Hz flicker responses and oscillatory potentials (OPs). Eight of the 12 examined patients showed abnormal ff-ERG results. OCT showed an attenuation of the RNFL in nine of the 12 patients, most often superiorly and/or inferiorly. None of the patients presented with temporal attenuation. Significant positive correlations (Spearman’s coefficient) were found between the total averaged RNFL thickness as well as the superior and inferior RNFL thickness and the reduced ff-ERG parameters (the b-wave amplitude of the combined response, 30 Hz flicker and OPs). Multifocal VEP amplitudes were significantly reduced in the patients compared to the controls, however, the method was found to be unsuitable for these patients since it triggered seizures.
Conclusions: :
Patients that had been exposed to vigabatrin medication showed an attenuation of the RNFL thickness assessed by OCT. Attenuation of the RNFL was correlated to reduced ff-ERG parameters, indicating that OCT of the RNFL may be used in order to facilitate the follow-up of patients on vigabatrin medication.
Keywords: drug toxicity/drug effects • retina • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)