Light and electron microscopy of the anterior chamber angle structures following surgical disinsertion of the ciliary muscle in the cynomolgus monkey.

Light and electron microscopic studies were done on 11 cynomolgus monkey eyes which had undergone total iris removal followed by surgical disinsertion of the ciliary muscle from the scleral spur 4.7 to 14.4 months earlier. Anterior chamber perfusion to measure gross outflow facility had been performed one to nine times postoperatively. Over most of the circumference in most eyes (1) the ciliary muscle had been retrodisplaced from the scleral spur and had reattached to the sclera more posteriorly; (2) ciliary muscle, trabecular meshwork, and Schlemm's canal appeared normal. A cyclodialysis cleft was never seen. Fixation of some eyes in the in vivo and in vitro presence of pilocarpine demonstrated the contractibility of the retrodisplaced muscle. In isolated areas where the ciliary body had been surgically cut, scar tissue of varying thickness connected scleral spur, sclera, ciliary body, zonule, and lens capsule, but did not infiltrate trabecular meshwork or Schlemm's canal. In such sectors, plasma cell-like cells replaced trabecular endothelial cells and were also present in the scar tissue, ciliary muscle, and surrounding vessel walls in the scar and sclera. In sectors of two eyes, a previously existing trabecular operculum extended posteriorly and completely covered the meshwork. The meshwork in these sectors was poorly perfused by aqueous humor, and electron-dense deposits were present beneath the inner wall of Schlemm's canal. Four totally iridectomized and two unoperated eyes from these monkeys were also examined; ciliary muscle, trabecular meshwork, and Schlemm's canal appeared normal in all, despite the numerous anterior chamber perfusions.