The effect of high-dose methylprednisolone on laser-induced retinal injury in primates: an electron microscopic study

Background: Previously we reported an ameliorative effect of high-dose methylprednisolone in laser injury to monkey retinas. The ultrastructural modification by methylprednisolone has not been examined. Methods: Cynomolgus monkeys were given severe (grade III) retinal laser bums and treated with an intravenous megadose of methylprednisolone. Pathologic features of the retinal lesions with or without methylprednisolone treatment were evaluated by light and electron microscopy. Results: Ultrastructurally, the treated lesions showed rapid recanalization of choriocapillaris; proliferation of retinal pigment epithelium to replace the necrotic and damaged cells, resulting in rapid re-establishment of blood retinal barrier; mild macrophagic activity; and rapid reformation of the outer limiting membrane by Mueller cells. Conclusion: A high dose of methylprednisolone affected the responses of the choriocapillaris, retinal pigment epithelium, photoreceptor cells and Mueller cells to laser injury, showing an overall beneficial effect. These modifications might be ascribed to methylprednisolone's anti-inflammatory action, protection of the microcirculation and anti-lipid peroxidation effect.