Lost and Slipped Muscles
A rectus muscle that sustains trauma or that slips out of the sutures or instruments while unattached to the globe during an operation can retract through the Tenon capsule and become inaccessible (“lost”) posteriorly in the orbit. This consequence is most severe when it involves the medial rectus muscle, because that muscle is the most difficult to recover.
The surgeon should immediately attempt to find the lost muscle, if possible with the assistance of a surgeon experienced in this potentially complex surgery. Malleable retractors and a headlight are helpful. Minimal manipulation should be used to bring into view the anatomical site through which the muscle and its sheath normally penetrate the Tenon capsule where, it is hoped, the distal end of the muscle can be recognized and captured. If inspection does not reliably indicate that the muscle has been identified, sudden bradycardia when traction is exerted can be confirmatory. Recovery of the medial rectus muscle has been achieved by using a transnasal endoscopic approach through the ethmoid sinus or by performing a medial orbitotomy. Transposition surgery may be required if the lost muscle is not found, but anterior segment ischemia may be a risk. Where to reattach the recovered muscle depends on several factors in the particular case and is largely a matter of judgment.
A slipped muscle is the result of inadequate imbrication of the muscle during strabismus surgery, which allows it to recede posteriorly within its capsule postoperatively. Clinically, the patient manifests a weakness of that muscle immediately postoperatively, with limited rotations and possibly decreased saccades in its field of action (Fig 14-1). Surgery should be performed as soon as possible in order to secure the muscle before further retraction and contracture take place.
In reoperations for strabismus with deficient rotations, slippage or a stretched scar should be suspected and the involved muscles explored. The pseudotendon must be excised to restore the function of the muscle.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.