Unilateral Proptosis Causes

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Proptosis is a bulging of the eyeball from the socket from one or both eyes. Unilateral or any asymmetrical protrusion or bulging of one eye by at least 2 millimeters is one way of recognizing the protrusion. The normal upper limit is 22 mm for whites, 24 mm for blacks, 21 mm for Asians, and 19.7 mm for Hispanics. This condition may lead to problems with visual acuity, as well as delayed activity in pupils. There are several possible causes of unilateral proptosis, including thyroid eye disease, Graves’ disease, tumors, and bleeding.

Thyroid Eye Disease

Thyroid eye disease offers eye symptoms around the same time the thyroid disease starts, but the eye condition can occur prior to or after the thyroid disease is treated. It is rare, but recurrence of the eye disease can occur with inadequate control of the hormone levels. Many patients with thyroid disease will never have eye troubles, but some patients do suffer from it mildly. Thyroid eye disease is thought to be brought on by thyroid dysfunction, but treatment of the thyroid doesn’t guarantee that the eye disease will get better. The eye disease can continue on for up to 3 years, with gradual improvement from treatment.

Graves’ Opthalmopathy

Dr. Revecca Bahn, MD states that Grave’s disease is caused when antibodies attack the thyroid and stimulate it to make too much thyroxine or T4. These antibodies then attack the protein in the cells of the eyes and can inadvertently cause them to bug out or bulge. This causes the metabolism to become erratic, and causes Graves’ opthalmopathy or swelling of the eyes to the point of protrusion.

Orbital and Lacrimal Gland Tumors

Dr. Paul Finfer, MD states that orbital tumors occur behind the eye and can push the eye forward causing proptosis. These tumors are not necessarily cancerous, but simply a clumping of cells that have grown outside of their normal areas. Lacrimal or tear gland tumors also occur behind the eye, but are known for causing the corner of the eye to swell, in turn causing the eye to bulge. Growths such as orbital tumors can be caused by inflammations such as pseudotumors and infection or abscesses.

Orbital Varix and Inflammatory Pseudotumors

An orbital varix is more or less a varicose vein that sits behind the eye. The vein in the eye socket or orbit is filled with blood, and it becomes enlarged more than normal. The extra blood causes the eye to protrude. Inflammatory pseudotumors are also known as inflammatory myofibroblastic tumors. These are made of cells that mix together and cause an irritation in the area they attach to. Pseudotumors are not actual tumors, but their behavior in the body being similar to tumors is how they got their name. Once the clump of cells builds up behind the eye, it causes proptosis or bulging of the eyes due to the pressure of the inflammatory pseudotumor.

Bleeding Behind the Eye

Bleeding behind the eye can be caused by head or facial trauma, or a break in the vascular system. When a small break in the vascular system is present, it causes the blood to break free from the artery or vein it was housed in. The area behind the eye, or the orbit, fills with blood when the ocular veins have a breach. This can be detected with CT scans.


Merck Manuals Online Medical Library from the article Proptosis last reviewed April 2009

Mayo Clinic from the article Unlocking the Mysteries of Graves’ Ophthalmopathy

EyeCancerNetwork.com from the article About Orbital Tumors: General Information