Acetylcholine intramuscular injection improves results of inferior oblique myectomy.

PURPOSE

To examine the effect of injecting acetylcholine into the remaining proximal segment of the inferior oblique muscle after distal myectomy.

METHODS

Twenty patients with inferior oblique overaction, 11 males and 9 females, were enrolled prospectively in the study: 14 with V type esotropia, 4 with V type exotropia, and 2 with paresis of the superior oblique muscle. At surgery, the inferior oblique muscle was identified, isolated on a muscle hook, cut free at its insertion, and freed of its facial attachments. After a 5 mm myectomy of the distal end the muscle body was then injected with 0.5 cc of acetylcholine (Miocholthorn ).

RESULTS

Eighteen out of 20 cases exhibited satisfactory results: postoperatively there was no inferior oblique overaction in 16, consecutive underaction in 2. Mild residual overaction remained in 2 patients. None, however, required additional surgery.

CONCLUSIONS

Our experience with injection of acetylcholine to the myectomized inferior oblique shows that it can, by stimulating contraction, enhance withdrawal and recession of the disinserted myectomized muscle and thereby eliminate undesirable reattachment near the original insertion. The end result is a lower incidence of persistence or recurrence of postoperative overaction and improved surgical results.