A broken blood vessel in the eye, known medically as a subconjunctival hemorrhage, is almost always caused by a brief spike in blood pressure through tiny veins. Coughing, sneezing, straining, or rubbing your eyes too hard are the most common triggers. The result is a bright red patch on the white of your eye that looks alarming but is rarely dangerous.
The clear membrane covering your eye (the conjunctiva) is packed with fragile capillaries. When one breaks, blood leaks into the space between that membrane and the white of the eye beneath it. Because there’s nowhere for the blood to go, it spreads out into a vivid red blotch that’s impossible to miss in the mirror.
Physical Triggers That Raise Venous Pressure
The most frequent cause is anything that briefly forces pressure upward through the veins in your head and face. A hard sneeze, a coughing fit, vomiting, or straining on the toilet can all produce enough of a pressure spike to pop a capillary. Heavy lifting, pushing, or bending forward does the same thing. Even vigorous eye rubbing can create enough mechanical force to rupture a vessel.
These events are so ordinary that most people never pinpoint exactly which one caused their hemorrhage. You might wake up with a red eye after a night of coughing from a cold, or notice it after a tough workout. In many cases, there’s no memorable event at all.
Medications That Increase the Risk
Blood thinners make broken eye vessels more likely because they reduce your blood’s ability to clot, allowing even minor vessel damage to produce visible bleeding. Aspirin and prescription anticoagulants like warfarin are the most commonly linked medications. In one study, patients who stayed on aspirin or warfarin before cataract surgery had a 10% higher rate of subconjunctival hemorrhage compared to those who stopped these medications a week beforehand.
Long-term use of steroid eye drops can also play a role. These medications weaken blood vessel walls over time, making them more fragile and prone to breaking with minimal trauma. This is most often seen in people using steroid drops for chronic eye inflammation.
High Blood Pressure and Other Health Conditions
If broken blood vessels in your eye keep coming back, the cause may be systemic rather than a random sneeze. High blood pressure is the single biggest medical risk factor. In a large study of over 17,600 people who experienced subconjunctival hemorrhages, about 32% had hypertension. Chronically elevated blood pressure damages the walls of small blood vessels throughout the body, including those in the eye, making them more susceptible to rupture.
Diabetes contributes through a similar mechanism. Over time, high blood sugar weakens capillary walls and disrupts the tiny blood vessels that supply the eye. High cholesterol and hardening of the arteries (arteriosclerosis) are also recognized risk factors. All of these conditions share a common thread: they degrade the structural integrity of small blood vessels, so less pressure is needed to cause a break.
Recurring subconjunctival hemorrhages, especially in someone who hasn’t had their blood pressure checked recently, can be worth mentioning to a doctor. Spontaneous broken eye vessels have been identified as a potential sign of undiagnosed hypertension.
Eye Injuries and Contact Lenses
Direct trauma to the eye is another straightforward cause. A poke, a bump, or even aggressive rubbing can rupture surface blood vessels. Contact lens wearers face slightly higher risk because the lens itself can create friction against the conjunctiva, and the act of inserting and removing lenses involves touching the eye daily. A poorly fitting lens or dry lens can increase that mechanical irritation.
What It Looks Like as It Heals
A fresh subconjunctival hemorrhage is bright red. Over the following days, it typically shifts through darker shades of red, then brownish, then yellowish-green as the body reabsorbs the trapped blood, much like a bruise on your skin. The whole process generally takes one to three weeks depending on the size of the bleed. Larger hemorrhages that cover more of the white of the eye take longer to clear.
During healing, the red patch may actually appear to spread before it shrinks. This is normal. The blood is simply diffusing through the tissue as it breaks down. You don’t need to treat it. Artificial tears can help if the eye feels mildly irritated, but the hemorrhage itself resolves on its own.
When a Red Eye Means Something Else
A subconjunctival hemorrhage is painless and doesn’t affect your vision. That’s the key distinction. If you have a red eye along with pain, light sensitivity, blurred vision, or discharge, something else is going on. Those symptoms can point to conditions like acute glaucoma, an eye infection, or inflammation inside the eye, all of which need prompt attention.
A broken blood vessel that follows a significant injury to the face or eye also warrants evaluation. Trauma-related hemorrhages can sometimes mask deeper damage that isn’t visible on the surface. And if you’re on blood thinners and notice frequent or unusually large hemorrhages, your medication levels may need checking to make sure they’re within the intended range.
For the vast majority of people, though, a single broken blood vessel is a cosmetic nuisance that clears up in a couple of weeks without any treatment at all.