Subconjunctival Hemorrhage
A subconjunctival hemorrhage looks alarming, a bright red patch on the white of your eye, but it's often painless and doesn't affect vision. At Dr. Della Chow, we confirm the cause, rule out anything more serious, and tell you what to expect as it heals.
Alarming to See, Harmless to Have: Subconjunctival Hemorrhage Explained
You glance in the mirror and a section of the white of your eye has turned solid, vivid red. Not bloodshot — properly red, with a clean edge to it, as though someone had painted it on overnight. It is one of the most startling things the eye can do.
It is also, in the overwhelming majority of cases, completely harmless. A subconjunctival hemorrhage looks far worse than it is, causes no pain, does not affect vision, and clears on its own. What follows is how to recognise it, what causes it, and the short list of situations where it is worth having someone look.
TL;DR: A subconjunctival hemorrhage is a bright red patch on the white of your eye caused by a burst blood vessel. It’s typically harmless, painless, and clears on its own within one to two weeks. See an optometrist if it comes with pain, vision changes, or follows an eye injury.
What Is a Subconjunctival Hemorrhage?
The conjunctiva is a thin, clear membrane covering the white of your eye. Running through it are tiny, fragile blood vessels. When one of them breaks, blood escapes and spreads out in the space between the conjunctiva and the white sclera underneath.
Because it is trapped between two smooth layers, the blood forms a flat, bright red patch with a sharply defined border rather than dispersing. It cannot get into the eye itself, and it is not sitting on the surface where you could wipe it away. It simply has to be reabsorbed, the same way a bruise clears.
That is the whole of it. A burst blood vessel in the eye is a bruise in an unusually visible place.
What It Looks Like — and What It Doesn’t Feel Like
The distinguishing feature of a subconjunctival hemorrhage is how little it does. A textbook one gives you:
A flat red patch with crisp edges, anywhere from a small spot to the entire visible white of the eye
No pain — at most a mild awareness or slight scratchiness
No change in vision — the blood is beside the cornea, not in front of the pupil
No discharge, no crusting, no stickiness in the morning
No light sensitivity
If all five of those hold, you are almost certainly looking at a simple hemorrhage that needs nothing but time. If any of them do not hold — particularly pain, blurred vision or discharge — the red eye is being caused by something else, and that is worth sorting out.
What Causes a Burst Blood Vessel in the Eye?
Ordinary pressure spikes
The most common causes are entirely mundane: a hard cough, a violent sneeze, vomiting, straining, heavy lifting, or bearing down. Each briefly raises pressure in the small veins of the head and neck, and a fragile vessel gives way. A bad cold or a heavy session at the gym accounts for a good share of the cases we see.
Rubbing and minor irritation
Vigorous eye rubbing does it, as can inserting or removing a contact lens awkwardly, or a fingernail catching the surface. Chronic rubbing has other downsides for the cornea, so it is a habit worth breaking regardless.
Medications and blood pressure
Blood thinners and antiplatelet medications — including everyday low-dose aspirin — make these more likely and more dramatic. So does uncontrolled high blood pressure, which is one reason a recurring hemorrhage is worth mentioning to your family doctor. Never stop or change a prescribed medication because of a red eye; the conversation to have is whether your current dose and blood pressure are where they should be.
Injury
Any blow to the eye or head can cause one. This is the category that changes the advice, because a hemorrhage from trauma can sit alongside damage that is not visible from the outside. Get examined.
No cause at all
Often there simply isn’t one to find. People wake up with a red eye having done nothing in particular, and that is a normal way for this to happen. The vessels are delicate and they become more so with age.
Is It a Burst Blood Vessel or Pink Eye?
These two get mistaken for each other constantly, and the difference is easy to see once you know what to look for.
A subconjunctival hemorrhage is a solid block of red with a defined edge, painless, with clear vision and no discharge. Conjunctivitis produces diffuse pink or red across the whole eye from dilated vessels you can still see individually, usually with grittiness, watering or discharge, and it often spreads to the second eye. If you are unsure which you are dealing with, our guide to whether pink eye is contagious covers the signs in detail.
The practical consequence matters: a hemorrhage is not contagious and requires nothing. Infectious conjunctivitis spreads readily and may need treatment. Guessing wrong in either direction is inconvenient.
| Feature | Subconjunctival Hemorrhage | Conjunctivitis (Pink Eye) |
|---|---|---|
| Appearance | Solid block of red with a defined edge | Diffuse pink or red across the whole eye |
| Discharge | None | Often present, watery or sticky |
| Contagious | No | Yes, if infectious |
| Treatment | None needed, resolves on its own | Depends on the cause; may need drops |
How Long Does It Take to Heal?
Most clear within one to two weeks, and larger ones can take up to three. The blood is reabsorbed gradually, and it changes colour on the way out exactly as a bruise on your arm would — bright red at first, then rust, then orange, then a yellowish green before disappearing.
It is common for it to look slightly worse on days two and three as the blood spreads and thins before it starts clearing. That is expected and not a sign anything is wrong.
There is no way to speed it up. Drops, warm compresses and cold compresses do not shorten the process, though artificial tears will settle any surface scratchiness while you wait.
What to Do While It Clears
Leave it alone. No treatment is needed and none will help it clear faster
Use preservative-free artificial tears if the eye feels scratchy
Avoid rubbing the eye, which risks breaking the same fragile vessel again
Ease off heavy lifting and straining for a few days if that is what caused it
Take a photo on day one. It gives you a reference for whether it is genuinely clearing
You can carry on wearing contact lenses if the eye is comfortable, though many people find a few days in glasses easier while the surface settles.
Red Flags: When to Get It Checked
Book an appointment or seek urgent care if the red eye comes with any of the following:
Pain — beyond mild scratchiness
Any change in vision — blurring, dimming, or new floaters
Discharge, crusting or stickiness, which suggests infection rather than bleeding
Marked light sensitivity
Recent injury to the eye or head, however minor it seemed
No improvement after three weeks, or a patch that is still spreading after the first few days
Both eyes at once, or bruising and bleeding elsewhere on your body
If you are getting flashes of light or a sudden increase in floaters alongside the redness, that combination points at the retina rather than the surface — see our guide to sudden black spots in vision and arrange same-day care.
When It Keeps Happening
A single hemorrhage means very little. Several within a few months is a pattern, and patterns are worth investigating — not because the eye is in danger, but because the eye is occasionally the first place a systemic issue shows itself.
Recurrent episodes usually prompt a blood pressure check, a review of any blood-thinning medication, and sometimes clotting tests through your family doctor. We will also examine the eye properly to confirm there is no local cause such as a lesion or chronic irritation, and check the health of the retinal vessels — the same vessels affected by diabetic eye disease and by long-standing hypertension.
Red Eye, Clear Answer
A subconjunctival hemorrhage is one of the few eye conditions where looking dramatic and being harmless go together — but that is only reassuring once someone has confirmed it is what you actually have.
If your eye has turned red and you are not certain what you are looking at, come and see us. It takes minutes to distinguish a simple hemorrhage from conjunctivitis, an injury, or one of the less common causes of a red eye, and you will leave knowing which it is. As your neighbourhood optometrist in Kitsilano, we would much rather check and reassure you than have you watching it in the mirror for a fortnight. Book an eye exam in Vancouver today.
This content is for educational purposes only and does not replace a professional eye exam or personalized medical advice. If your red eye comes with pain, vision changes, or follows an injury, contact your optometrist promptly.
Medical disclaimer: This article is for general education and is not a substitute for an individualized eye exam. If you’re experiencing symptoms, please book an assessment so we can look at your specific situation.
Got Questions? We’ve Got Answers
What causes a burst blood vessel in the eye?
A small vessel in the conjunctiva breaks and blood spreads under the surface. The most frequent triggers are coughing, sneezing, vomiting, straining or heavy lifting, eye rubbing, and minor trauma. Blood thinners and high blood pressure make it more likely. Often no cause is found at all.
How do you heal a subconjunctival hemorrhage?
You do not need to. It clears on its own in one to two weeks as the blood is reabsorbed, fading through red, orange and yellow like a bruise. Artificial tears help if the eye feels scratchy, but nothing shortens the process.
What are the red flags for a subconjunctival hemorrhage?
Pain, changed vision, discharge, strong light sensitivity, recent injury to the eye or head, no improvement after three weeks, both eyes affected at once, or unusual bruising and bleeding elsewhere. Any of these means it should be examined rather than waited out.
Does a subconjunctival hemorrhage affect your vision?
No. The blood sits over the white of the eye, not the cornea or pupil, so it does not obstruct sight. Any blurring or dimming means something else is going on and should be checked.
Is a burst blood vessel in the eye contagious?
Not at all — it is a bruise, not an infection. That is one of the clearest ways to tell it apart from conjunctivitis, which does spread.
Should I go to the emergency room for a red eye?
Not for a painless red patch with normal vision. Do seek urgent care if there was an injury, if you have pain or vision changes, or if the eye is red following any blow to the head.