Blood in the eye usually means a tiny blood vessel on the surface of the eye has burst, creating a bright red patch on the white part. This is called a subconjunctival hemorrhage, and it looks far worse than it is. Most cases heal on their own within two weeks without any treatment. But blood that appears in other parts of the eye, especially if accompanied by pain or vision changes, can signal something more serious.
The Most Common Cause: A Broken Surface Vessel
The white of your eye is covered by a thin, clear membrane packed with tiny blood vessels. When one of those vessels breaks, blood gets trapped beneath the membrane and spreads across the white of the eye. You might notice a small red dot or a large, vivid red patch that covers a significant portion of the eye’s surface. It can look alarming, but it’s painless and doesn’t affect your vision at all.
These surface hemorrhages happen more often than most people realize. Common physical triggers include hard sneezing, coughing, vomiting, straining during a bowel movement, or heavy lifting. Rubbing your eyes too roughly can do it. Sometimes you wake up with one and have no idea what caused it. The blood gradually changes color as it’s reabsorbed, sometimes shifting to yellow or green before disappearing completely, much like a bruise on your skin. Most heal within two weeks, though larger spots can take a bit longer.
What Makes Surface Hemorrhages More Likely
Certain medications increase your risk. Blood thinners like warfarin and aspirin reduce your blood’s ability to clot, which means even minor stress on a vessel can cause visible bleeding. Over-the-counter pain relievers like ibuprofen have a similar, milder effect. If you take any of these and notice frequent broken blood vessels in your eye, it’s worth mentioning to your doctor, though it doesn’t necessarily mean you need to change your medication.
High blood pressure and diabetes both weaken blood vessels over time, making them more fragile and prone to rupture. Recurring subconjunctival hemorrhages, particularly if you’re not on blood thinners and can’t identify an obvious trigger like a coughing fit, can sometimes be an early clue that blood pressure or blood sugar needs better management. A single episode is rarely a cause for concern. A pattern of them is worth investigating.
Blood Behind the Colored Part of the Eye
A hyphema is a different and more serious condition where blood collects in the front chamber of the eye, the fluid-filled space between the cornea and the iris (the colored ring). Instead of a red patch on the white of the eye, you might see blood pooling in front of or around the iris. This type of bleeding typically causes pain and can blur your vision, which distinguishes it clearly from a harmless surface hemorrhage.
Hyphemas are most often caused by a direct blow to the eye, the kind of impact that happens during sports, a fall, or an accident. They require prompt medical attention because blood pooling in that chamber can raise pressure inside the eye and potentially damage your vision if left untreated. Both a hyphema and a surface hemorrhage can occur at the same time after a significant eye injury.
Bleeding Deeper Inside the Eye
The back of the eye is filled with a clear, gel-like substance that helps maintain the eye’s shape. When blood leaks into this space, it’s called a vitreous hemorrhage. You won’t see a red patch from the outside. Instead, the symptoms are visual: sudden floaters, cobweb-like shadows, a reddish tint to your vision, or in more severe cases, significant vision loss that comes on quickly.
This deeper bleeding has two broad categories of causes. The first is mechanical: a direct injury to the eye, a retinal tear, or the gel naturally pulling away from the retina as you age (which can strain and snap small connecting blood vessels). Intense pressure changes inside the head, from severe coughing or straining, can occasionally trigger it too.
The second category involves underlying diseases that weaken the eye’s blood vessels over time. Diabetic retinopathy is one of the most common culprits. High blood pressure, sickle cell disease, blocked retinal veins, wet age-related macular degeneration, and blood disorders like hemophilia can all cause vessels inside the eye to leak or rupture. Vitreous hemorrhage always warrants a medical evaluation because identifying and treating the underlying cause is essential to protecting your vision long-term.
How to Tell What You’re Dealing With
The key factors that separate a harmless broken vessel from something requiring attention are pain, vision changes, and location of the blood.
- No pain, no vision changes, red patch on the white of the eye: Almost certainly a subconjunctival hemorrhage. Safe to monitor at home.
- Pain with visible blood near the iris: Likely a hyphema. Needs same-day medical evaluation, especially after any kind of eye trauma.
- Sudden floaters, shadow-like streaks, or vision loss without visible external redness: Could indicate bleeding inside the eye. Needs prompt evaluation.
- Recurring surface hemorrhages with no obvious trigger: The individual episodes are harmless, but the pattern may point to uncontrolled blood pressure, a clotting issue, or a medication side effect worth reviewing.
Caring for a Broken Surface Vessel
A standard subconjunctival hemorrhage doesn’t need treatment. Your body reabsorbs the trapped blood on its own over one to two weeks. If the eye feels mildly irritated or scratchy, preservative-free artificial tears (lubricating eye drops) can help with comfort. Avoid rubbing the affected eye, which can slow healing or potentially cause more vessel damage.
You don’t need to avoid screens, reading, or normal activities. The hemorrhage won’t spread to the other eye, and it isn’t contagious. If you’re taking blood thinners, don’t stop them because of a broken vessel in your eye. The hemorrhage is cosmetically annoying but medically insignificant in the vast majority of cases. If the redness hasn’t improved after two to three weeks, or if you develop pain or vision changes at any point during healing, that’s when a medical evaluation becomes important.