Developmental immaturity of the trabecular meshwork in congenital glaucoma.

We examined nine specimens of anterior chamber angle tissue obtained by trabeculectomy from seven patients with early-onset congenital glaucoma and one patient with late-onset congenital glaucoma by light and electron microscopy and compared them with specimens of trabecular meshwork from normal human and monkey eyes. One eye with early-onset congenital glaucoma had no Schlemm's canal. In all cases of congenital glaucoma, we observed a thick subcanalicular tissue with a structure similar to that seen in the endothelial meshwork beneath the inner wall of Schlemm's canal. There were abnormal deposits of ground substances that resembled basement membrane. Additionally, histologic studies of eyes from premature infants obtained at autopsy showed that trabecular sheet-formation initially occurs on the anterior chamber side of the trabeculum and advances gradually toward Schlemm's canal and that the undifferentiated portion of the trabeculum remains as endothelial meshwork beneath the inner wall of Schlemm's canal. Our observations strongly suggest that the existence of the thick subcanalicular tissue, which is considered to be endothelial meshwork, indicates an immature stage of the trabecular meshwork and may be one of the primary causes of increased intraocular pressure in congenital glaucoma.