Fast and slow artificial diurnal rhythms (light-darkness-light) and the rate of progression of retinal degeneration in dystrophic RCS rats. An electroretinographic study.

The RCS rat strain is characterized by a hereditary progressive degeneration of retina and pigment epithelium. The possible influence of varying artificial diurnal rhythms on the rate of progression of the degeneration was investigated with electroretinography (ERG). Light intensity of the 'day'-periods and the total light exposure were constant in two groups of RCS rats subjected to 2 h light/2 h darkness and to 24 h light/24 h darkness periods respectively. No difference in the rate of degeneration as mirrored by the ERG was seen between the two groups. The ERGs were unrecordable after 7-8 weeks, and the experiments started at birth. No changes in the ERG of controls, genetically identical with the RCS strain except for the retinal dystrophy gene, were seen when they were subjected to the two diurnal rhythms. The results lessen the probability that careful long-term patching of an eye in patients with retinitis pigmentosa or other related hereditary degenerative diseases (in order to diminish the influence of diurnal illumination changes leading to shedding of receptor outer segments) will halt or modify the progression of the disease in man.