Transnasal endoscopic approach to expose the medial rectus from the annulus of Zinn to the penetration of Tenon's capsule.

Conventional strabismus surgery employs a conjunctival incision to gain access to Tenon's space where a wide variety of procedures are routinely performed on the tendon and anterior aspect of the extraocular muscles. Recently, transnasal endoscopic surgical techniques have gained acceptance as effective means of decompressing the medial wall and floor of the orbit in patients with thyroid-related orbitopathy. The orbital surface of the medial rectus and inferior rectus are exposed from the annulus of Zinn to a position close to where the muscles penetrate Tenon's capsule. In theory, this technique also provides the exposure necessary to locate and retrieve a "lost" medial rectus when the usual sub-Tenon's approach fails to recover the muscle. Cadaver studies demonstrate the feasibility of exposure and suture placement in the stump of a lost medial rectus with passage of the suture through Tenon's capsule to transmit the force of the muscle to the globe, provided that the lost muscle is retrieved before severe contracture develops.