Strabismus After Cataract Surgery

Abstract

In addition to traditionally cited causes for strabismus after cataract surgery, myotoxicity from inadvertent intramuscular injection of the local anesthetic has become recognized as an infrequent but potent cause of strabismus following retrobulbar or peribulbar anesthesia in elderly individuals. Initial paresis of the extraocular muscle, with diplopia the day after surgery, is often followed by localized fibrosis of the muscle, first with resolution of the diplopia but then with progressing diplopia in the opposite direction over a several week period.Histopathologic studies in monkeys and humans have demonstrated widespread destruction of muscle fibers from commonly used local anesthetics, with resulting scar formation in elderly individuals. Cadaver studies have shown that an inferotemporal injection with an inch-and-a-half needle can reach any of the extraocular muscles, and indeed patients have been identified with involvement of each of the muscles, sometimes with more than one muscle involved.Mild fibrosis causes an overaction pattern; more extensive fibrosis causes a restrictive pattern. Characteristic Lancaster red-green test results help identify this syndrome. Recession of the involved muscle, best performed using adjustable sutures, is usually successful and gratifying.Administration of local anesthetics by alternative routes, such as by a sub-Tenon's infusion, should be considered for ocular surgery.