An electrophysiological approach to metal intoxication of the eye

Intoxication of the retina, caused by penetration of foreign metallic substances into the eye, induces pathological changes (Knave 1970; Schmidt and Strube 1972). Copper is one of the most dangerous and frequently found in such eye's injuries. In order to find a simple criterion for justifying the need for emergency at operation, the electrophysiological response of the retina was tested as expressed by the electroretinogram (ERG) and the visual evoked potential (VEP). While the ERG represents mainly changes in the photoreceptor level, the VEP indicates the effect on the retinal ganglion layer. Experiments were carried out on anesthetized cats in which particles of metallic copper (2 mm long, 0.5 mm dia.) had been implanted in the vitreous humor. The electrophysiological recordings were done following one week, two weeks, one month and two months from the implantation. The ERG and the VEP were significantly affected; changes were found in amplitude as well as in latency. The intensity of the responses found seem to be mainly dependent on the distance of the copper implant from the retina. The degree of retinal toxicity may be thus affected by the amount of free copper ions released from the implant.