[Sensitive physiologic perceptual tests for ocular side effects of drugs exemplified by various anticonvulsants]

Advanced psychophysical tests, performed in 42 patients who have seizures, showed that the widely used antiepileptic drugs, diphenylhydantoin and carbamazepine, can specifically affect retinal function, while valproic acid and the epileptic seizures do not. The Farnsworth-Munsell 100-Hue and Panel D-15 désaturé tests revealed an accumulation of errors along the tritan/tetartan axis and a high total error score. As shown by measurement of the so-called transient tritanopia and by determination of the spectral sensitivity, this blue vision defect is not only due to loss of postreceptoral interaction between long- and short-wavelength-sensitive cones, but is also based on a disturbance in the receptor mechanism itself. The dark adaptation curve was not affected. As determined by cone flicker thresholds during dark adaptation, the inhibitory action of rods on cones is reduced. The results obtained for mesopic vision and especially glare sensitivity measured by nyktometry were markedly affected in these patients compared to the normal population. The psychophysical methods provide a very sensitive test for early detection of drug-induced retinal dysfunction and allow clear differentiation between the loss of a receptor mechanism and a defect in the neuronal interaction between photoreceptors in the human visual system induced by antiepileptics.