Natural course of anterior segment ischemia after disinsertion of extraocular rectus muscles in an animal model.

Purpose To compare the frequency and severity of anterior segment ischemia (ASI) after disinsertion of extraocular rectus muscles in a rabbit eye model. Methods The rectus muscles of eyes of 84 rabbits were removed. In 42 rabbits one eye underwent three-muscle surgery, whereas the fellow eye underwent two-muscle surgery. In the other 42 rabbits, one eye underwent three-muscle surgery and the fellow eye four-muscle surgery. The surgery included disinsertion together with extirpation of the anterior 10 mm of the muscle. Each eye was examined daily to detect the presence of ASI. Anti-inflammatory eyedrops were not used in any subject. The severity of inflammation and time to complete resolution of inflammatory signs were documented. After inflammation resolved, both eyes of each rabbit were enucleated and studied by a pathologist. Results The incidence of ASI was 9.5% in the two-muscle group, 31% in the three-muscle group, and 50% in the four-muscle group ( P  = 0.001). ASI eyes all developed signs on the first postoperative day. Inflammation resolved in 4-38 days. The incidence of ASI increased significantly with the number of muscles operated on. Permanent complications were rare and histopathology results were normal in most cases. Conclusions Inflammation resolved spontaneously in all involved eyes without intervention and only minor clinical or pathologic changes were noted. One eye, however, developed severe sequela but was still preserved. The severity of ASI was directly correlated to the number of operated rectus muscles. Our findings suggest a self-limited nature of ASI in this rabbit model.