Dr. Dean

Why Do I Have One Watery Eye?

Posting Date: 09/26/2000

Original broadcast date: August 10, 2000

Neal: My right eye is watering day in and day out, and I can't control it. I can see okay though and it's not red.

After giving me a complete checkup, the ophthalmologist said the cause is probably allergies. I do have a history of allergies, but I think allergies would cause both eyes to water.

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Dr. Dean: Good for you. You can't have an allergy in only one eye. Also, allergies would make your eyes red and itchy.

I can think of two causes of your one watery eye: a blocked tear duct or, paradoxically enough, a dry eye.

We don't notice, but we continually make tears which drain out through the nose. This is why your nose runs when you cry.

I was once stumped by a caller who asked me why the color blue was running out of her nose. It was another woman who knew the answer, because she too had had blue discharge caused by mascara and eyeliner getting into her tears and running out her nose.

If a tear duct is blocked, your tears can't get into your nose and will run over the edge of your eyelid.

The second possibility, a dry eye as a cause of a watery eye sounds contradictory, but here's how it works.

Two systems produce tears. One is the tear gland, which provides a lot of tears when you suddenly need them, like when you cry or get something in your eye.

The second system is the baseline system that keeps your eye continually moist. If for someone reason, this baseline system fails and your eye dries out, the first system -- the tear gland -- goes on overtime. It kicks in and produces so many tears that they overflow. So a dry eye can actually cause tearing.

Whatever the cause is, the ophthalmologist didn't find it. You need to return to the doctor, or see a different one, and ask to be tested for a blocked tear duct or for dry eye.