Abstract
ObjectiveEpilepsy is a debilitating disease. Visual function changes have been reported and may be attributed to the epileptic changes or as a result of medication side effect. Sodium valproate and carbamazepine are both first line anti-epileptic medications used in Malaysian health care. Sodium valproate inhibits glutamate and γ-aminobutyric acid (GABA) transaminase while carbamazepine acts on the sodium channel - both are an important part of the retina. This study aimed to compare the visual functions of epilepsy patients on carbamazepine or sodium valproate monotherapy.DesignA cross-sectional study was conducted at a tertiary hospital between June 2016 and November 2018.MethodsPatients with idiopathic epilepsy that fulfill the inclusion and exclusion criteria were recruited from the neurology clinic. They were divided into two groups and underwent complete eye examinations. Visual functions such as color vision testing, contrast sensitivity, visual field and retinal nerve fiber layer measurement were subsequently performed. Statistical analysis was done using Statistical Package for the Social Science, version 24 (SPSS Inc, Chicago, IL, USA).ResultsA total of 100 patients (sodium valproate: 50 patients; carbamazepine: 50 patients) were recruited for the study. There were no statistically significant changes in anatomical or visual function between the sodium valproate and carbamazepine group. However, patients from both groups displayed color vision defect in the blue and green axes. Changes in color vision could indicate early retina toxicity secondary to the medication. Although there were no visual field changes, patients recorded a slight reduction of mean deviation. Changes of mean deviation could be attributed to the side effect of medication or the disease process.ConclusionsEpileptic patients taking sodium valproate or carbamazepine did not demonstrate statistically significant change in visual function.
Highlights
Epilepsy is a debilitating disease with a considerable economic burden
Sodium valproate inhibits glutamate and γ-aminobutyric acid (GABA) transaminase while carbamazepine acts on the sodium channel - both are an important part of the retina
This study aimed to compare the visual functions of epilepsy patients on carbamazepine or sodium valproate monotherapy
Summary
The continent of Asia is home to some of the world’s largest and poorest population with estimates of 25 million epileptics [1]. A recent study placed the prevalence of epilepsy in Malaysians at an estimate of 12.3% to 25.3% [2]. The postulated pathway for the development of epilepsy includes imbalance in the neurotransmission signaling pathway and ion channel receptors. Glutamate and γaminobutyric acid (GABA) are important neurotransmitters in the brain. It is hypothesized that imbalance between the glutamate-mediated excitation and GABA-mediated inhibition results in the occurrence of seizure [3,4,5,6]. Cation channels generate action potential which contribute to axon excitability, while anions are inhibitory. Imbalance between ion channels is postulated to cause epilepsy [9]
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