The combined effects of light and acute ischemia on the structure of the rabbit retina: a light and electron microscopic study.

The ultrastructure of the rabbit retina has been investigated to determine the combined effects of light and ischemia. Both eyes of 16 adult Dutch rabbits were exposed to light of an intensity known to be near or below the threshold for ultrastructural changes in the retina. In addition, one eye of each animal was subjected to one of four periods of pressure-induced total acute ischemia. Exposure to light alone resulted in only minor disturbances of the receptor cell outer segments. The remainder of the retina was of normal morphologic appearance. Exposure to the combined insults of light exposure and ischemia produced considerably more damage to the inner and outer retina. Light exposure combined with short periods of ischemia (15 to 30 min) resulted in edema of the pigment epithelium and disturbances of the receptor cell inner and outer segments. Light exposure combined with longer ischemic periods (45 to 60 min) resulted in severe disturbances in the structure of the pigment epithelium, breakdown of the receptor cell outer segments, rupture of the inner segment mitochondria, and severe edema of the neural retina. The implication of this addictive or synergistic action of light and ischemia is discussed.