Orbit is the bony socket lined with fatty tissue that cradles and protects the eye.
The bony structure includes the cheekbone, forehead bone, temple bone, and bridge of the nose. Unlike other bones in the body, these eye protectors usually do not weaken and thin with age.
The globe of the eye is held in place in the orbit by six extrinsic muscles. Upper and lower eyelids protect the front of the eyeball by blocking dirt and bright light that can damage the eyes. The eyelids also lubricate the eyeball with each blink – which happens every few seconds. Blinking washes away dust, pollen, and other foreign bodies.
The lubricant, called tears, comes from the glands above each eye. When something irritates the eye, as vapors from peeling an onion, the tear glands open up. If tearing is slight, the fluid will drain through tiny ducts within each eyelid and into the nose, taking the irritants with it. However, the drainage system cannot handle such fully-opened “faucets” as a full cry, when tears run down the cheeks.
The orbit is subject to several conditions. The fatty tissue surrounding the globe may become inflamed from a bacterial infection which may spread to the globe.
Tumors may also form within the orbit. Hemangioma, a common tumor of the orbit most often seen in children, is benign and rarely requires surgery. Dermoid cyst is a growth that appears at the level of the eyebrow in the upper portion of the orbit. The cyst may be removed for cosmetic reasons and for biopsy. Pseudotumor is an inflammatory mass of the orbit without a known cause. This tumor is treated with steroids to reduce the inflammation.
Other rare tumors include glioma of the optic nerve and rhabdomyosarcoma. Glioma of the optic nerve is a slow-growing tumor that causes optic atrophy. It may be linked with Von Recklinghausen’s disease.
Rhabdomyosarcoma is a rare tumor of the orbit seen in children. It is highly malignant and rapid growing, but may be controlled by radiation therapy if caught in its earliest stages. Tumors originating from diseases of the body may metastasize to the orbit.
Tumors of the orbit often cause diploma (double vision) or exophthalmos, bulging of the eyes. Exophthalmos (proptosis) is usually caused by a thyroid dysfunction, muscle palsy, injury, and infection. Enophthalmos, the appearance of sunken eyeballs, may occur because of an injury that displaces the fatty tissue lining of the orbit.
Injuries to the orbit may result in vision-limiting conditions. A common injury, the blow-out fracture, occurs when the globe is forced back into the orbit. A fracture forms on the orbital floor and bone is forced downward. Such an injury often causes damage to the rectus muscle and infraorbital nerve.
The injury may be treated with placement of a plastic implant in the orbital floor and return of the displaced tissue to its correct position. Fractures of the skull may extend into the orbit and cause cranial nerve palsy or optic nerve damage. A blow to the eye may result in optic disc atrophy. Such conditions resulting from injuries may affect vision or result in vision loss.
