Figure 14-9 Patient treated for left hypertropia by recession of the right inferior rectus muscle, which pulled the right lower eyelid down, and resection of the left inferior rectus muscle, which pulled the left lower eyelid up.

Changes in eyelid position can be obviated somewhat by careful dissection. In general, all intermuscular septum and fascial connections of the operated vertical rectus muscle must be severed at least 12–15 mm posterior to the muscle insertion, although doing this is contrary to the view of many surgeons that there should be minimal disturbance of the Tenon capsule. Release of the lower eyelid retractors or advancement of the capsulopalpebral head is helpful to prevent lower eyelid retraction after inferior rectus muscle recession.

Refractive Changes

Changes in refractive error are most common when strabismus surgery is performed on 2 rectus muscles of an eye. An induced astigmatism of low magnitude usually resolves within a few months.

Anesthesia for Extraocular Muscle Surgery

Methods

In cooperative patients, topical anesthetic drops alone (eg, tetracaine 0.5%, proparacaine 0.5%, lidocaine 2%) are effective for most steps in an EOM surgical procedure. Lid blocks are not necessary if the eyelid speculum is not spread to the point of causing the patient pain. Topical anesthesia is not effective for control of the pain produced by pulling on or against a restricted muscle or for cases in which exposure is difficult.

Both local infiltration (peribulbar) and retrobulbar anesthesia make most EOM procedures pain free and should be considered in adults for whom general anesthesia may pose an undue hazard. The administration of a short-acting hypnotic by an anesthesiologist just before retrobulbar injection greatly improves patient comfort. Because injected anesthetics may influence alignment during the first few hours after surgery, suture adjustment is best delayed for at least half a day.

General anesthesia is necessary for children and is frequently used for adults as well, particularly those requiring bilateral surgery. Neuromuscular blocking agents such as succinylcholine, which are administered to facilitate intubation for general anesthesia, can temporarily affect the results of a traction test. Nondepolarizing agents, which do not have this effect, can be employed instead.