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Abstract
Diplopia, blurred vision and colour disturbances are well-known side effects associated with anti-epileptic drugs (AEDs). Farnsworth-Munsell 100-hue colour test (F-100) is an accepted and sensitive tool to detect changes in colour perception. To determine the impact of AEDs upon colour vision, we evaluated 37 consecutive patients with complex partial seizures exposed to monotherapy with phenytoin (PHT, carbamazepine (CBZ) or valproic acid (VPA). All had normal IQ and no congenital disturbances in colour vision or ocular diseases. Twenty normal controls were used for statistical analysis. Thirteen patients were exposed to PHT, 12 to CBZ and 12 to VPA. Visual colour perception was impaired in 30/37 (82%) of the study group. The most significant abnormality was detected in the blue-yellow axis in 10/13 patients exposed to PHT (p < 0.02) and in 8/12 treated with CBZ (p < 0.009). In 8/12 patients taking VPA, no significant abnormality was observed (p < 0.06). None of the studied patients complained of colour vision disturbances. Our findings strongly support the negative effect of AEDs
upon colour vision discrimination, most likely due to changes at the retinal processing level. F-100 proved to be very useful to assess early toxicity due to AEDs.
Key Words
Colour discrimination Epileptic patients Farnsworth-Munsell 100-hue test
Introduction
Epilepsy is a chronic disorder which may be well controlled with anti-epileptic drugs (AEDs) in 70-75% of cases [ 1 ]. Several studies comparing safety and efficacy of these drugs have shown that phenytoin (PHT), carbamazepine (CBZ) and valproic acid (VPA) are the drugs of choice for patients with partial seizures with or without secondary tonic-clonic generalization [2]. Although the underlying mechanisms of action of these drugs is not well established, it is accepted that most affect primarily neurotransmission and/or membrane conductance [3].
AED effects upon visual and oculomotor performance have been described, including colour perception and visual contrast sensitivity impairment [4]. The main abnormality reported in the literature in such patients was in the blue-yellow axis, which seems to indicate retinal dysfunction.
The aim of our work was to validate the FarnsworthMunsell 100-hue test (F-100), a sensitive clinical test for colour discrimination, in epileptic patients exposed to single-AED therapy and to examine the relationship with doses and length of treatment.
Patients and Methods