[Insertion of the Tenon capsule onto the rectus muscles]

The localisation and definition of the capsule of Tenon insertion on the rectus muscles is of prime importance to the strabismus surgeon. The depth of the superior sub-Tenon space was measured on 22 adult human eyes after fixation in formalin. Although the measurements revealed major differences between the eyes, the following results were found: inferior rectus muscle = 7.8 mm +/- 1.79 (5.2-13.0), medial rectus = 12.6 mm +/- 2.15 (8.4-17.2), superior rectus muscle = 16.7 mm +/- 2.39 (12.7-21.5), and lateral rectus muscle = 19.0 mm +/- 2.19 (14.5-22.0). Histological studies of 2 other human eyes confirmed the notion of a band of insertion on rectus muscles as the posterior limit of the sub-Tenon space. As far as this insertion, the capsule of Tenon is a dense connective tissue composed of many collagen and elastin fibers, but after the band insertion, it becomes virtual through its fusion with the perimysium of the rectus muscle.