Ultrastructural changes in the trabecular meshwork of human eyes treated with corticosteroids.

Objectives: To study the ultrastructure of the trabecular meshwork in human eyes with corticosteroid-induced glaucoma and to determine whether the changes noted also occur in the eyes of patients with primary open-angle glaucoma (POAG) who have been treated with corticosteroids.

Methods: The trabecular meshwork from 5 patients in whom corticosteroid-induced glaucoma was diagnosed and from 6 patients with POAG who had been treated with systemic or topical corticosteroids for months to years was investigated with light and electron microscopy. None of the eyes with POAG were considered to have corticosteroid-induced elevation of the intraocular pressure.

Results: Eyes with corticosteroid-induced glaucoma had the accumulation of extracellular material distinct from the sheath-derived plaques typical of POAG. A finger-printlike arranged material resembling basement membranes (FBM material), considered characteristic of corticosteroid-induced glaucoma, was found in all eyes with corticosteroid-induced glaucoma. In addition, an abnormal accumulation of densely packed, fine fibrils immediately beneath the inner wall endothelium of Schlemm's canal was present. The findings were similar among patients receiving topical or systemic treatment and among patients of different ages. In the eyes from donors with POAG who had been treated with corticosteroids, the fine fibrillar material and FBM material were present in small amounts in 3 of 6 donors and were not found in the other 3 donors.

Conclusions: The extracellular material that accumulates in eyes with corticosteroid-induced glaucoma differs from that seen in eyes with POAG. Eyes with POAG exposed to long-term corticosteroid treatment did not all respond with the formation of the abnormal extracellular materials characteristic of those found in eyes with corticosteroid-induced glaucoma.