Abstract
Abstract: :
Purpose: Weakening by selective removal of layers of extraocular muscle could be clinically useful. Method: We used multiple applications of a holmium laser on the orbital surface of rectus muscles in 11 rabbits and 3 monkeys. The retina is protected by a metal scleral shield. Results: In monkeys, the initial effect is a general weakening creating a strabismus of up to 15 degrees, a reduction in rotation amplitude, and a reduction of peak saccadic velocity in the pulling direction of the treated muscle of 30 to 60% on day one after treatment. We suppose that these functional effects are due to penetration of all layers by the radiation; they gradually diminished over one to two weeks. There was no restriction to rotation out of the field of action of the treated muscle. Histologically, the orbital layer was removed over the anterior 2/3 of the muscle, the global layer and nerve supply appeared intact. Scarring was modest in amount. A laser fiber inserted through a needle destroyed muscle tissue about 1.0 mm in diameter along the length of the needle track in the muscle. Three such penetrations created functional effects similar to surface application. Conclusion: Laser ablation may have value as a clinical treatment for strabismus. Support: NIH Grant EY12216
Keywords: 591 strabismus: treatment • 405 extraocular muscles: structure