The authors describe the macroscopic, histological, and ultrastructural findings observed in an experimental animal model of the fadenoperation . Grossly, muscular fibrosis and musculo-scleral adhesions were well established after the second postoperative month. Histologic findings demonstrated the development of a granulomatous, foreign body reaction around the musculo-scleral fixation suture, collagenization of the muscle tissue from the first postoperative month and degenerative phenomena in the muscle fibers. Electron transmission microscopic study showed atrophy and angulation with distortion of the myofibrillar matrix, along with alteration of the Z bands of muscle fibers, mitochondrial alteration, and dilatation of the sarcotubular system. All these experimental findings suggest the relative irreversible effects of the fadenoperation after the early postoperative period and for the first time, demonstrated that this surgical technique alters the muscle structure.