Tenon's capsule

The fascia bulbi (also known as the capsule of Ténon and the bulbar sheath) is a thin membrane which envelops the eyeball from the optic nerve to the limbus, separating it from the orbital fat and forming a socket in which it plays.

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Its inner surface is smooth, and is separated from the outer surface of the sclera by the periscleral lymph space.

This lymph space is continuous with the subdural and subarachnoid cavities, and is traversed by delicate bands of connective tissue which extend between the fascia and the sclera.

The fascia is perforated behind by the ciliary vessels and nerves, and fuses with the sheath of the optic nerve and with the sclera around the entrance of the optic nerve.

In front it blends with the conjunctiva, and with it is attached to the ciliary region of the eyeball.

The structure was named after Jacques-René Tenon (1724-1816), a French surgeon and pathologist.

Relations to extraocular muscles

It is perforated by the tendons of the ocular muscles, and is reflected backward on each as a tubular sheath.

The sheath of the Obliquus superior is carried as far as the fibrous pulley of that muscle; that on the Obliquus inferior reaches as far as the floor of the orbit, to which it gives off a slip.

The sheaths on the recti are gradually lost in the perimysium, but they give off important expansions.

The expansion from the Rectus superior blends with the tendon of the Levator palpebrae; that of the Rectus inferior is attached to the inferior tarsus.

The expansions from the sheaths of the Recti lateralis and medialis are strong, especially that from the latter muscle, and are attached to the lacrimal and zygomatic bones respectively.

As they probably check the actions of these two Recti they have been named the medial and lateral check ligaments.

Charles Barrett Lockwood described a thickening of the lower part of the fascia bulbi, which he named the 'suspensory ligament of the eye'. It is slung like a hammock below the eyeball, being expanded in the center, and narrow at its extremities which are attached to the zygomatic and lacrimal bones respectively.