If a blood vessel breaks in your eye, the result may look frightening, but your vision is probably not at risk. The white part of the eye (sclera) is covered by a thin, clear membrane called the conjunctiva. Tiny blood vessels under the conjunctiva provide oxygen and nutrients to the surface of the eye. If one of these tiny blood vessels breaks, the condition is called a subconjunctival hemorrhage.

The first and probably only symptom of a subconjunctival hemorrhage is the appearance of your eye. When you look in the mirror, the white part of the eye around the iris may look bright red. The red area can be extensive, or may be just a small fleck of red somewhere on the eye. Your eye may feel slightly scratchy, but your vision should not be affected, and there should be no pain or discharge from the eye.

In most cases, the cause of the subconjunctival hemorrhage is not known. The following factors may be involved in developing a broken blood vessel in the eye:

• Trauma to the eye
• Blood pressure – if you lift a heavy object, cough, sneeze, laugh, vomit, or are constipated, the extra pressure could cause a blood vessel to rupture.
• Blood thinners – if you are taking blood thinners such as aspirin or warfarin (sometime sold as the brand name Coumadin), you may be at increased risk of bleeding into the white of the eye if your blood is too thin.
• Blood clotting disorders – in rare cases, a blood clotting disorder or a vitamin K deficiency can cause this type of bleeding.

Other risk factors may include having diabetes and using certain herbal supplements such as ginkgo. Subconjunctival hemorrhages are more common in newborn infants. It is believed that this is caused by the changes in pressure around the baby’s body during childbirth.

If you see a subconjunctival hemorrhage in your eye, you should see your eye care professional to be sure the cause is a simple broken blood vessel and not a more serious problem. If unusual eye redness is accompanied by a sudden change in vision, pain, or strong sensitivity to light, see your eye doctor right away as this could be a more serious condition that should have immediate treatment.

Subconjunctival hemorrhages heal themselves in seven to 10 days, so no treatment is required. Because the blood is trapped in the layer between the conjunctiva and the sclera, it will simply take time for the eye to clear. In some cases, as the bright red color fades, the area may go through color changes similar to when a bruise is healing. Eye drops will not aid the healing process, but If your eye is scratchy or uncomfortable, they may make ease the irritation.

Sources:
All About Vision
National Institutes of Health: Medline Plus
Mayo Clinic