Fiber hypertrophy in rat extraocular muscle following lateral rectus resection

Compensatory hypertrophy of muscle fibers occurs when tension on a skeletal muscle is increased. We looked for this phenomenon in response to strabismus surgery by performing a large right lateral rectus resection in 16 rats. Muscle fiber diameters of all horizontal rectus muscles were measured at 2-week postoperative intervals. Significant fiber hypertrophy occurred in both the antagonist right medial rectus and the resected right lateral rectus within 4 weeks. Fiber diameter subsequently returned to baseline in both muscles. We postulate that fiber hypertrophy in this setting may be a compensatory response to increased elastic load.