The role of oxygen in retrolental fibroplasia.

The effects of oxygen in the immature or incompletely vascularized retina are conveniently divided into an initial vasoconstrictive and obliterative stage and a secondary vasoproliferative response that occurs after removal of the subject from an enriched oxygen environment. Vasoproliferation starts at the zone of perfused and nonperfused retina. The incompletely vascularized retina is uniquely responsive to these oxygen-induced changes. After vascularization is complete and the retinal vessels reach the ora, the susceptibility to hyperoxia disappears. The vessels in the temporal periphery of the retina have a peculiar susceptibility to the primary and secondary effects of hyperoxia on the immature retina. Ophthalmoscopic examination of the temporal periphery therefore should always be done carefully in the premature infant or in older individuals giving a history of prematurity. The indirect ophthalmoscope provides the most satisfactory instrument for examination. The incidence of retrolental fibroplasia has been greatly reduced following the incrimination of oxygen as its principal cause. Further studies are still required to determine precise blood oxygen levels that are safe for the premature retina and to discover other factors that may play a role in the pathogenesis or RLF.