19 research outputs found
The peripheral and Central Humphrey visual field â morphological changes during aging
Modelling the Risk of Visual Field Loss Arising from Long-Term Exposure to the Antiepileptic Drug Vigabatrin: A Cross-Sectional Approach
Background:
The antiepileptic drug vigabatrin has been used widely since 1989, but has only been approved for use in the US since 2009. The risk:benefit of vigabatrin is generally predicated upon an assumed frequency of associated visual field loss (VAVFL) of approximately 31 %. This estimate is based upon relatively short-term usage (up to 4â5 years) and it is essential to determine whether the frequency of VAVFL increases with longer-term usage.
Objective:
The aim of this study was to model, from cross-sectional evidence, over greater ranges of treatment duration and cumulative dose than previously evaluated, the risk (frequency) of VAVFL with increasing exposure to vigabatrin.
Study Design and Setting
This was a retrospective cohort study undertaken in a regional hospital epilepsy clinic.
Patients:
The cohort comprised 147 consecutive patients treated with vigabatrin for refractory complex partial (focal) seizures, who had all undergone ophthalmological examination and who had undertaken perimetry, reliably, according to a standard and robust protocol. The visual field plots were evaluated masked to treatment duration and dose.
Main Outcome Measure:
The risk (frequency) of VAVFL with increasing exposure to vigabatrin was modelled, from the cross-sectional evidence, by standard and plateau logistic regression.
Results:
The cohort comprised 80 females and 67 males (mean age 40.3 years, standard deviation 13.7). The median duration of vigabatrin exposure was 7.9 years (interquartile range 3.6â11.0, range 0.2â16.1 years); 46 patients (31 %) had received vigabatrin for over 10 years. Eighty-seven patients (59 %) exhibited VAVFL; the proportion with VAVFL was higher in males (66 %) than females (54 %). The plateau model for duration and for cumulative dose exhibited a better fit than the standard model (both p < 0.001). The modelled frequency of VAVFL increased with increasing exposure up to approximately 6 years duration and 5 kg cumulative dose, and plateaued at approximately 76 % (95 % CI 67â85) and 79 % (95 % CI 70â87), respectively. Severity of VAVFL, classified in terms of the visual field index Mean Deviation, was not significantly associated with either duration or cumulative dose of therapy.
Conclusion:
Clinicians and patients, in enabling informed choice, should be alert to the possible substantial increased risk:benefit for VAVFL with increasing long-term exposure to vigabatrin and the ensuing increased cost:benefit resulting from the necessary additional visual assessments