Effect of extraocular muscle surgery on corneal topography.

A computerized videokeratoscopy system was used to evaluate changes in corneal topography after muscle surgery in 36 eyes of 18 rabbits. Topographic analysis revealed a significant flattening of the cornea in the superior and superotemporal octants after superior rectus recession (mean +/- SE, -1.78 +/- 0.16 diopters) compared with control eyes undergoing a sham procedure (-0.17 +/- 0.18 D; P less than .05). Excision of all rectus muscles caused a generalized corneal flattening (-1.42 +/- 0.13 D; P less than .001). A computerized, finite element model of the globe, including the rectus muscles, demonstrated corneal deformation as a result of extraocular muscle tension; recession of an extraocular muscle in this model caused corneal flattening in the quadrant of the recessed muscle. These data suggest that corneal topography is affected by extraocular muscle tension, corroborating clinical reports of refractive change after strabismus surgery.