Anatomy of Tenons capsule.

BACKGROUND

The microscopic and macroscopic anatomy of the anterior and posterior Tenons capsule is described.

METHODS

An observational anatomic study of twelve orbits of 6 cadavers (mean age 79.5 years) were examined microscopically and 8 orbits of 4 cadavers (mean age 76.8 years) were examined macroscopically. After orbital exenteration, an X-shaped incision was made in the specimens to include the posterior part of the globe. The sections were divided into four parts: superomedial; inferomedial; superolateral; and inferolateral. In the macroscopically examined specimens, the eyelids and globes were removed from the exenterated tissues and the appearance of Tenons capsule was studied.

RESULTS

In the microscopic study, Tenons capsule covered the sclera beneath the conjunctiva and contained smooth muscle fibres in the anterior area. This anterior fascia, which had a thick appearance, reached the globe equator. From there, the capsule of the orbital fat, which contained no smooth muscle fibres, enveloped the sclera and reached the optic nerve. This was defined as the posterior capsule. In the macroscopic specimens, Tenons capsule had a thick and fibrous white appearance in the anterior area. More posteriorly, the capsule was thinner and more translucent. This thin capsular part was generally larger in the lateral area than in the medial area.

CONCLUSIONS

Tenons capsule is composed of an anterior thick fibrous tissue comprising the orbital smooth muscle network and the posterior thin fibrous capsule of the orbital fat.