A bright red patch suddenly appearing on the white of the eye is a startling sight that often prompts immediate concern. While the dramatic appearance suggests a severe problem, a burst blood vessel on the eye’s surface is frequently benign. This common phenomenon can be caused by a forceful cough or an underlying health condition. Understanding the reasons for this bleeding helps differentiate a harmless incident from one that warrants medical attention.
What Happens When a Vessel Bursts
The most frequent cause of blood appearing on the eye’s surface is a Subconjunctival Hemorrhage (SCH), the rupture of a tiny blood vessel beneath the conjunctiva. The conjunctiva is the transparent membrane covering the white part of the eye (sclera) and the inner surface of the eyelids. When a vessel breaks, the released blood becomes trapped between the sclera and the conjunctiva.
Because the conjunctiva cannot quickly absorb the blood, it pools into a sharply defined, bright red patch. This distinct coloration makes the event look alarming, though the condition is typically painless and does not affect vision. Like a bruise, the blood naturally reabsorbs over one to two weeks without specific treatment.
Everyday Reasons for Rupture
Many burst vessels are linked to sudden, sharp increases in internal pressure, often called the Valsalva maneuver. Any physical action causing intense straining leads to a momentary spike in venous pressure in the head and neck, rupturing delicate conjunctival capillaries. Common triggers include severe coughing, powerful sneezing, straining during a bowel movement, or intense vomiting.
Heavy physical exertion, like lifting heavy weights or intense resistance training, can also generate transient pressure. Minor trauma is another frequent cause, occurring from vigorously rubbing the eyes or an accidental poke. Even errors during contact lens insertion or removal can create sufficient local irritation and pressure to break a small vessel.
Environmental factors that cause irritation and dryness may also contribute. Excessive eye rubbing prompted by allergies or a foreign body can weaken the small vessels and increase the likelihood of hemorrhage. These mechanical causes represent the majority of cases and are not indicative of a serious health issue.
Systemic Health Factors
While many cases result from benign physical actions, a burst vessel can signal an underlying systemic factor affecting blood vessel integrity or clotting ability. Chronic, uncontrolled high blood pressure (hypertension) is a recognized risk factor because it exerts constant stress on the walls of small, fragile blood vessels. This continuous pressure makes the vessels more prone to spontaneous rupture.
Certain medications also increase the susceptibility to bleeding by interfering with natural clotting mechanisms. Anticoagulant drugs (blood thinners) and antiplatelet medications like aspirin reduce the risk of internal clots, but cause broken vessels to bleed more freely. Individuals with blood clotting disorders are inherently more likely to experience spontaneous or recurrent hemorrhages.
In older individuals, conditions like diabetes and arteriosclerosis can weaken the vascular walls. This makes the small vessels more brittle and susceptible to breaking under minor stress.
Warning Signs Requiring a Doctor Visit
While most subconjunctival hemorrhages are harmless, specific accompanying symptoms indicate the need for medical evaluation. A burst blood vessel associated with eye pain, discharge, or any noticeable change in vision (such as blurriness or loss) should prompt an immediate visit to a healthcare provider. These additional symptoms suggest a potential problem beyond a simple surface vessel rupture.
If the red patch does not begin to clear within one to two weeks, or if hemorrhages occur frequently without apparent cause, consultation is necessary. Recurrent bleeding may point to an undiagnosed systemic issue, such as poorly controlled hypertension or a bleeding disorder. Any burst vessel following significant trauma to the head or eye requires a comprehensive examination to rule out more serious internal injuries.