DEAR MAYO CLINIC: After many tests, including an MRI and an MRA, I was told that I had a mass behind my right eye. I was tentatively diagnosed with orbital varix. My symptoms include fullness in my forehead, tightness across my eye and top of my nose and, on occasion, a feeling that my eye is being pulled toward the back of my head. I have no real pain and my eyesight is unaffected, however I am extremely uncomfortable and receiving no treatment or medication. Who would be able to make a definite diagnosis and can orbital varix be treated?

ANSWER: A simple way to think about an orbital varix is that it's similar to a varicose vein. A vein in your eye socket (orbit) fills with blood causing it to become enlarged beyond its normal diameter. The excess blood in the distended vein causes the eye to protrude and results in the symptoms you mention. Usually, the vein fills when a person bends over or strains. When the excess blood drains out of the vein, the symptoms go away.

Your doctor may suspect orbital varix if you have a history of pain or protrusion of the eye when you exert yourself, such as when lifting a heavy object. A physician can usually make a definitive diagnosis of orbital varix using imaging tests, such as CT scanning, magnetic resonance imaging (MRI) or color-flow Doppler ultrasound. The tests usually are done with and without a Valsalva maneuver. An example of a Valsalva maneuver is when you forcefully try to exhale without letting the air escape. Enlargement of the vein will show during the Valsalva maneuver.

Many times, the best treatment for orbital varix is to avoid the activities that cause symptoms. Only a small percentage of those affected by orbital varix require additional treatment. Over time, however, symptoms can get worse in some people. Should treatment become necessary, surgery may be an option. One technique that can be used, called embolization, involves reducing blood flow to the vein by injecting a sticky compound (cyanoacrylate) into it, followed by surgery to remove the vein that has just been embolized.

Surgery behind the eye can be technically difficult because many nerves, eye muscles, and blood vessels are concentrated into a small space. Injury to any of these could result in vision loss, double vision, a droopy eyelid or unequal pupil size.

To confirm your diagnosis, consult an ophthalmologist who has experience treating orbital varix. Also, discuss with your physician if surgery for orbital varix is appropriate in your situation, and, if so, the surgical risks and benefits. -- James Garrity, M.D., Ophthalmology, Mayo Clinic, Rochester, Minn.