Tenon's capsule (), also known as the Tenon capsule, fascial sheath of the eyeball () or the fascia bulbi, is a thin membrane which envelops the eyeball from the

optic nerve In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual information from the retina to the brain. In humans, the optic nerve is derived fro ...

to the corneal limbus, separating it from the orbital fat and forming a socket in which it moves. The inner surface of Tenon's capsule is smooth and is separated from the outer surface of the

sclera The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some crucial elastic fiber. In humans, and so ...

by the periscleral lymph space. This lymph space is continuous with the subdural and

subarachnoid In anatomy, the meninges (, ''singular:'' meninx ( or ), ) are the three membranes that envelop the brain and spinal cord. In mammals, the meninges are the dura mater, the arachnoid mater, and the pia mater. Cerebrospinal fluid is located in t ...

cavities and is traversed by delicate bands of connective tissue which extend between the capsule and the sclera. The capsule 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

. In front it adheres to the

conjunctiva The conjunctiva is a thin mucous membrane that lines the inside of the eyelids and covers the sclera (the white of the eye). It is composed of non-keratinized, stratified squamous epithelium with goblet cells, stratified columnar epithel ...

, and both structures are attached to the ciliary region of the eyeball. The structure was named after Jacques-René Tenon (1724–1816), a French surgeon and pathologist.

Structure

Relations

Tenon's capsule 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, and that on the

obliquus inferior The inferior oblique muscle or obliquus oculi inferior is a thin, narrow muscle placed near the anterior margin of the floor of the orbit. The inferior oblique is one of the extraocular muscles, and is attached to the maxillary bone (origin) and ...

reaches as far as the floor of the

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...

, to which it gives off a slip. The sheaths on the recti muscles 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, and that of the

rectus inferior The inferior rectus muscle is a muscle in the orbit near the eye. It is one of the four recti muscles in the group of extraocular muscles. It originates from the common tendinous ring, and inserts into the anteroinferior surface of the eye. It dep ...

is attached to the

inferior tarsus The tarsi (tarsal plates) are two comparatively thick, elongated plates of dense connective tissue, about in length for the upper eyelid and 5 mm for the lower eyelid; one is found in each eyelid, and contributes to its form and support. Th ...

; it is the space which lies between the sclera and the capsule. The expansions from the sheaths of the recti lateralis and medialis are strong, especially that from the latter muscle, and are attached to the zygomatic bone and lacrimal bone respectively; as they probably check the actions of these two recti, they have been named the medial and lateral

check ligaments In anatomy, the alar ligaments are ligaments which connect the dens (a bony protrusion on the second cervical vertebra) to tubercles on the medial side of the occipital condyle. They are short, tough, fibrous cords that attach on the skull a ...

Charles Barrett Lockwood Charles Barrett Lockwood (23 September 1856 – 8 November 1914) was a British surgeon and anatomist who practiced surgery at St. Bartholomew's Hospital in London. Lockwood was a member of the Royal College of Surgeons. Lockwood is remembere ...

described a thickening of the lower part of Tenon's capsule, which he named the

suspensory ligament of the eye The suspensory ligament of eyeball (or Lockwood's ligament) forms a hammock stretching below the eyeball between the medial and lateral check ligaments and enclosing the inferior rectus and inferior oblique muscles of the eye. It is a thickening of ...

. 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.

Clinical significance

Inflammation

Tenon's capsule may be affected by a disease called idiopathic orbital inflammation, a condition of unknown etiology that is characterized by inflammation of one or more layers of the eye. The disease is also known as orbital inflammatory pseudotumor, and sometimes may only affect the lacrimal gland or the

extraocular muscles The extraocular muscles (extrinsic ocular muscles), are the seven extrinsic muscles of the human eye. Six of the extraocular muscles, the four recti muscles, and the superior and inferior oblique muscles, control movement of the eye and the oth ...

Local anaesthesia

Local anaesthetic may be instilled into the space between Tenon's capsule and the sclera to provide anaesthesia for eye surgery, principally cataract surgery. After applying local anaesthetic drops to anaesthetise the

, a small fold of conjunctiva is lifted off the eyeball and an incision made. A blunt, curved cannula is passed through the incision into the periscleral lymph space and a volume of

local anaesthetic A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates an absence of pain in a specific location of the body without a loss of consciousness, as opposed to a general a ...

solution is instilled. The advantages are a reduced risk of bleeding and of penetration of the globe, compared to peribulbar and

retrobulbar A retrobulbar block is a regional anesthetic nerve block in the retrobulbar space, the area located behind the globe of the eye. Injection of local anesthetic into this space constitutes the retrobulbar block. This injection provides akinesia o ...

approaches. Akinesia (paralysis of the external eye muscles) may be less complete, however.

References

{{Accessory organs of the eye Human eye anatomy Fascia