DEAR DR. DONOHUE: Last week at work, my fellow workers told me I had blood in my eye. I looked in the mirror and saw a bright-red patch of blood in my left eye. They wanted me to go to the emergency room, but I said I would see my own doctor later. I never did. Since there was no pain and my vision was perfect, I didn’t think I needed to. The blood is fading. What caused it? – J.A.

ANSWER: In all probability it was a subconjunctival hemorrhage. The conjunctiva is a clear, cellophanelike wrap that covers the front of the eye and keeps it free from all the particles floating in the air. Under (hence the sub) the conjunctiva are many fine blood vessels, too fine to see. They break easily and bleed, leaving a red patch on the eye.

Any blow to the eye can cause vessels to break. Even a cough or sneeze, or straining to lift something heavy can break one of the vessels. These bleeds are almost never an indication of any serious problem, and they don’t affect sight. Warm compresses on closed eyelids hasten resolution of the blood.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com