Summary:Purpose: To describe concentric visual field loss found in the presurgical evaluation of patients with drugresistant temporal lobe epilepsy and relate the findings to potential causative factors.Methods: A series of 157 consecutive patients with drugresistant temporal lobe epilepsy, who had been selected for neurosurgical treatment, was examined in a study set up as a prospective investigation of their visual fields, to document the loss of visual field resulting from surgery. Pre-as well as postoperative visual field examinations were performed following a standard protocol using static and kinetic perimetry. As a number of patients appeared to have an unexplained concentric visual field contraction in the presurgical examination, a relation with potentially causative factors was analyzed in a crosssectional study of all these patients. Correlations were sought with duration and severity of the seizure disorder, underlying pathology as indicated by magnetic resonance imaging (MRI) and demonstrated by pathology, any type of antiepileptic drug (AED) ever prescribed, and gender.Results: In this cross-sectoinal analysis of 157 consecutive patients who were candidates for surgery for temporal lobe epilepsy, absolute concentric contraction of the visual field of 10 to 30 degrees was found in the presurgical examination in 20 (17%) of 11 8 patients who had ever used vigabatrin (VGB) and in none of 39 who had not had this medication. This difference was significant (p = 0.004). In addition, men [I5 (21%) of 721 were significantly more often affected (p = 0.007) than women [five (6%) of 851. The degree of visual field loss, as indicated by the Esterman grid, showed a positive correlation with the duration of VGB medication. There was no correlation of visual field contraction with a history of meningitis as potential cause of the epilepsy, duration of the epilepsy, status epilepticus in the medical history, or histologic abnormality of the brain tissue removed. Ophthalmologic examination of the patients with concentric contraction revealed no abnormalities. None of the patients with concentric contraction complained spontaneously of their visual field loss.Conclusions: VGB medication is a causative factor in concentric visual field loss. Visual field examination of patients using VGB should be seriously considered.

Summary:  Purpose: To describe the correlation between visual field loss and the duration, dosage, and total amount of vigabatrin (VGB) medication in a group of patients with epilepsy. Co‐medication of antiepileptic drugs (AEDs) and compliance were also studied. Methods: Ninety‐two patients (53 male and 39 female) taking VGB medication in the past or the present, attending the Outpatient Epilepsy Clinic in Utrecht, were examined with the Goldmann perimeter. The amount of visual field loss was calculated by the Esterman grid method and by a new method, with which the percentage surface loss of the visual field is measured. A complete drug history was compiled, specifying the amount and duration of VGB medication. Concomitant AED medication was noted. Serum levels of AEDs were determined. Results: Linear regression showed the total amount of VGB as the most significant parameter to predict visual field loss (p < 0.001). Further, men were more affected than women (p = 0.026). Compliance was good, and other AEDs did not influence the results. Conclusions: Because prolonged use of VGB medication is correlated with the amount of visual field loss, VGB should be prescribed only when there are no alternatives. In such cases, we recommend an examination of the peripheral visual field before starting therapy and a repeated examination every 6 months.

ABSTRACT.Background: To report the results of repeated electrophysiological and visual field examinations in patients with vigabatrin-associated visual field loss (VGB-VFL) and the relationship between these electrophysiological findings, the cumulative dose of vigabatrin and the extent of visual field loss. Methods: Twenty-two eyes of 11 patients with VGB-VFL were studied. All patients underwent surgery for therapy-resistant epilepsy. Repeated electrooculograms (EOGs) and flash electroretinograms (ERGs) were made and the cumulative dose of vigabatrin and the visual field loss were recorded after a period of 37-47 months. Results: The visual field loss was stable in patients who had stopped vigabatrin at the time of the first examination. There was a slight increase in VFL in patients who continued vigabatrin. During the second EOG and ERG, abnormalities in scotopic and photopic a-wave latencies and in scotopic b-wave amplitude were found in more than 50% of patients. Only b-wave latency became normal, while EOG, a-wave latency, a-wave amplitude and b-wave amplitude stayed abnormal. The amount of VFL and the cumulative dose of vigabatrin were statistically correlated with the b-wave amplitude, mainly photopic, found during the first and second examinations. Conclusion: After 4 years, EOG, flash ERG and visual field loss had not improved in patients with VGB-VFL. The statistically significant correlation found during the first examination between the amount of VFL and the cumulative dose of vigabatrin with the (mainly photopic) b-wave amplitude remained constant.

Summary:Purpose: To describe the correlation between visual field loss and the duration, dosage, and total amount of vigabatrin (VGB) medication in a group of patients with epilepsy. Co-medication of antiepileptic drugs (AEDs) and compliance were also studied.Methods: Ninety-two patients (53 male and 39 female) taking VGB medication in the past or the present, attending the Outpatient Epilepsy Clinic in Utrecht, were examined with the Goldmann perimeter. The amount of visual field loss was calculated by the Esterman grid method and by a new method, with which the percentage surface loss of the visual field is measured. A complete drug history was compiled, specifying the amount and duration of VGB medication. Concomitant AED medication was noted. Serum levels of AEDs were determined.Results: Linear regression showed the total amount of VGB as the most significant parameter to predict visual field loss (p < 0.001). Further, men were more affected than women (p ‫ס‬ 0.026). Compliance was good, and other AEDs did not influence the results.Conclusions: Because prolonged use of VGB medication is correlated with the amount of visual field loss, VGB should be prescribed only when there are no alternatives. In such cases, we recommend an examination of the peripheral visual field before starting therapy and a repeated examination every 6 months. Key Words: Visual field loss-Cumulative dose of vigabatrin-Epilepsy-Compliance-AED.After the first publication by Eke (1), the number of reports indicating that vigabatrin (VGB) is the cause of concentric contraction of the visual field has been rapidly increasing (1-15). In a selected group of patients with drug-resistant temporal lobe epilepsy accepted for neurosurgery, we found a statistically significant correlation between visual field loss and the use of VGB (16). In the same group of patients, we found that the visual field loss did not recover after VGB had been stopped for an average period of 2.5 years. Progression of the visual field loss was noted when VGB was continued (17). To date there is no good and simple method to quantify the visual field loss. The Esterman score has disadvantages, such as the unequal distribution of the 100 dots over the four quadrants and the missing points in the far periphery (18). We have therefore developed a new method, with which we calculate the percentage absolute surface loss of the visual field, and have compared the results with the Esterman grid. The purpose of the present study was to examine the relation between dosage and duration of VGB use and visual field in a population of patients with epilepsy, not selected for neurosurgery, who used VGB medication at some period in the course of their disease. The influence of co-medication of antiepileptic drugs (AEDs) and compliance also was studied. MATERIALS AND METHODS PatientsThe examination took place in the Outpatient Epilepsy Clinic Utrecht. Most patients were referred with therapyresistant epilepsy by their neurologists in general hospitals. A consecutive series of 112 patien...

ABSTRACT.Purpose: To determine the value of electrophysiological findings in patients with temporal lobe epilepsy and to relate these findings to the amount of concentric contraction of the visual field and the use of vigabatrin. Methods: Electro-retinograms and electro-oculograms were done on 30 patients, operated for temporal lobe epilepsy. The patients were divided into three groups: (A) concentric contraction of the visual field associated with a history of vigabatrin medication (15 patients), (B) normal visual field with vigabatrin use (11 patients) and (C) normal visual field without vigabatrin medication (4 patients).Results: Electrophysiological abnormalities were found in 50% of the patients in group A. The Arden ratio of the EOG was lowered in 57%. Abnormalities in the ERG were found: b-wave implicit time photopic F was prolonged (50%), b-wave amplitudes scotopic B (53%), C (73%) and G (50%) and photopic H (50%) were diminished. The amount of visual field loss and the total dose of vigabatrin used, showed only slight correlation with the ERG and EOG. The use of vigabatrin during the ERG and EOG recording in group A, gave a higher b-wave amplitude scotopic G in 64% of cases. The a-wave implicit times scotopic G (73%) and photopic G (59%) and H (73%) were shortened in group B. Conclusion: EOG was abnormal in 57% in group A. ERG abnormalities could only be found in 50% of group A, mainly in the inner retina. Since also the total dose of vigabatrin and the amount of visual field loss did not really show a correlation with the electrophysiological findings and results of literature are not unanimous, electrophysiology does not appear at present to be a good method to detect patients with, or at risk of, vigabatrin associated visual field loss. Regularly performed visual field examination remains the cornerstone in screening.