PURPOSE: To investigate the cause of secondary open-angle glaucoma due to sarcoidosis.

DESIGN: Observational case series studied by histological methods.

METHODS: Seven trabeculectomy specimens from six patients with secondary open-angle glaucoma due to ocular sarcoidosis (trabeculectomy group) and anterior parts of seven autopsy eyes from four patients (autopsy eye group) diagnosed as confirmed sarcoidosis were processed for light and transmission electron microscopy. Pathological changes of outflow routes were investigated.

RESULTS: Granulomata were found in three eyes of the trabeculectomy group and in three eyes of the autopsy eye group. Part of the Schlemm canal was occluded and replaced by fibrotic tissue and it became narrow in four eyes of the trabeculectomy group and three eyes of the autopsy eye group. The spaces of the trabecular meshwork appeared wide, even in the area close to granulomata and peripheral anterior synechia of the iris. Infiltration of lymphocytes, monocytes, and macrophages around the Schlemm canal was found in all eyes of the trabeculectomy group and in four eyes of the autopsy eye group. The infiltration of these cells was observed not only in the inner wall, but also in the posterior outer wall of the Schlemm canal and the collector channels.

CONCLUSION: “Schlemm canalitis” is proposed from the results of inflammatory cell infiltration around the wall of the canal. The occlusion of the Schlemm canal by granulomata or fibrotic tissue replacement of the canal may play an important role in secondary open-angle glaucoma due to sarcoidosis.