The site of reattachment of the extraocular muscle following hang-back recession.

The use of "hang-back" suspensions has been shown to be an effective means of weakening rectus muscles. The exact position where the muscle reattaches to the globe has, however, been questioned. We performed eight large hang-back recessions on the rectus muscles of cynomolgus monkeys. Eight weeks postoperatively the attachment sites were determined by reexploration. Six of the recessions were within 0.5 mm of the intended site. The muscles were found an average of 0.4 mm anterior to the intended position. These results confirm that the muscle reattaches close to the intended location. Eight exaggerated recessions were similarly performed; these were more variable in the site of reattachment. Only three muscles were reattached within 0.5 mm of the intended site. There was a mean forward reattachment of 1.1 mm. Four of the 16 muscles were found reattached by a pseudotendon rather than directly to the sclera.