On the time course of retina damage and regeneration after intravenous application of vincristine as monitored by visual light response.

The alkaloid vincristine is used for the chemotherapy of tumours in man. In rabbits and rats it is known to cause alterations in the retina, such as a globular deformation of the photoreceptor outer segments. The electroretinograms of human patients treated with vincristine of an equivalent dose, however, did not indicate considerable retina destruction as had been anticipated. In order to explain this discrepancy a comprehensive study was performed using the retina of albino rats which is electrophysiologically very well characterized. After vincristine injection, electron micrographs of the retina as well as extracellular recordings of its electric activity dependent upon the time p.i. consistently showed that transient retinal defects appeared in a mosaic-like distribution. Small areas completely degenerated and did not show any electric activity whereas other areas were normal. Therefore, transretinal measurements such as the electroretinogram should represent an average effect of the electric response of the retina. Half-life time for development of the maximum vincristine effect was 50 h whereas the regeneration of a full electrophysiological photo response was obtained in a further 70 h. The vincristine effect could be used as a model for the generation of some retinal diseases.