The conjunctiva contains many blood vessels and capillaries, the tiniest blood vessels in the body. These vessels can break, causing blood to leak between the conjunctiva and the sclera. This minor bleeding under the eye's outer membrane is what causes the bright red spot to appear on the white of the eye.
The most common causes are coughing, sneezing, straining, or any similar action that temporarily raises blood pressure in the veins, leading to a small rupture in a blood vessel or capillary. Subconjunctival hemorrhage can also occur because of trauma to the eye — even minor trauma such as rubbing the eye vigorously.
Other common but less frequent causes of subconjunctival hemorrhage include diabetes mellitus, high blood pressure, and excessive amounts of certain medications such as aspirin or blood thinners like warfarin (Coumadin®), which affect the body’s bleeding mechanisms.
Much less frequent to rare causes may include blood clotting disorders or other systemic blood disorders.
If you have recurrent or excessive subconjunctival hemorrhages, your ophthalmologist (Eye M.D.) will examine your eyes, assess your risk factors and order appropriate laboratory studies, if needed, sometimes in collaboration with your primary care physician.
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