A bright red patch on the white of the eye: subconjunctival haemorrhage in adults, and when it needs a doctor

A bright red patch appears on the white of the eye, often discovered in the bathroom mirror, and it looks far worse than it feels. In most adults it is a small bleed under the surface, called a subconjunctival haemorrhage, and it clears by itself. A few cases are not that simple, and this article separates the two.

What is the bright red patch on the white of my eye?

It is blood trapped under the conjunctiva, the thin clear membrane that covers the white of the eye. The American Academy of Ophthalmology describes it as one or more blood spots on the white of the eye, caused by tiny vessels in the conjunctiva breaking. It is a bruise of the eye surface, and it is usually painless.

The blood sits between the conjunctiva and the tissue under it, which StatPearls calls the Tenon capsule, a thin sheet of connective tissue around the eyeball. The vessels here are small and sit close to the surface with little support, so a minor rise in pressure or a small strain can split one. Because the conjunctiva is clear, the blood shows as a sharply edged, bright red patch, and a little blood spreads a long way. That is why a small leak looks dramatic.

The bleed is on the surface, not inside the eye. StatPearls notes that it does not cause pain, light sensitivity, reduced vision or a change in the pupil. Those missing features are the useful part. They are what tell a harmless surface bleed from a more serious eye problem, and I come back to them below.

What causes a burst blood vessel in the eye?

Often nothing you can name. EyeWiki states that up to 40 per cent of cases have no known cause. When there is a trigger, the AAO lists coughing, sneezing, straining, a knock to the eye and rubbing the eyes too hard, all of which briefly raise the pressure in the small vessels. Vomiting and heavy lifting belong in the same group.

Contact lens wear and a rough rub can add a small injury to the surface. Dry, gritty eyes make people rub more, so if your eyes are often dry the habit may be part of the story; the common eyelid-margin cause is in my article on dry eyes that start after fifty.

Age shifts the picture. StatPearls says younger people more often have a traumatic or spontaneous bleed, while older adults with high blood pressure or diabetes face the greatest risk. The AAO also lists blood thinning medicines, such as aspirin and anticoagulants, among the less common causes, and blood clotting disorders among the rare ones.

An important line, because it is the one people get wrong: a single, small, painless patch after a cough does not mean something is wrong with your blood vessels or your brain. It is common, and in a well person it is usually just that.

How long does it take to clear, and does it need treatment?

Most patches fade within one to two weeks, and the NHS says a red eye with no pain, normal sight and no sense of being unwell may get better on its own in a few days. EyeWiki gives one to four weeks, depending on the size. A larger bleed takes longer than a small one.

The colour changes as it clears, and this is normal. StatPearls describes the patch starting bright red, darkening to a deeper red, and finally taking a yellow-green tint as the blood pigment is broken down, much like a bruise on the skin. A yellow edge is a sign of healing, not of something new.

Nothing speeds it up. EyeWiki says no treatment has been shown to hasten resolution, and the AAO says it generally needs none. If the eye feels gritty or irritated, the AAO says artificial tears may help. These are lubricating drops, and they are safe to use as often as the packet advises.

What helps in practice is leaving the eye alone. The NHS advises not touching or rubbing the eye and not wearing contact lenses until it has settled. Do not stop aspirin or any other prescribed blood thinner because of a red patch. That decision belongs to the person who prescribed it, and I come to it below.

When is a red eye not a simple burst vessel?

When it comes with pain, light sensitivity, reduced vision, a sticky discharge or a history of significant injury. StatPearls states that a simple haemorrhage causes no pain, no light sensitivity, no reduced vision and no pupil change, so any of those points elsewhere.

Several conditions can look similar at first glance:

• Conjunctivitis, inflammation of the conjunctiva, makes the whole eye pink or red rather than leaving one sharp patch. The NHS lists a gritty or burning feel and sticky eyes with it.
• Episcleritis, inflammation of the thin layer just under the conjunctiva, gives a more diffuse, sectoral redness, and the eye may ache. It is a diagnosis for an eye doctor to make.
• A raised or growing lesion on the surface, which can bleed, is not an ordinary bruise. A patch that does not fade, or a lump that is still there once the red has gone, should be examined. EyeWiki notes that recurrent haemorrhage may signal serious disease, including malignancy.
• Bleeding after significant injury is a different problem. EyeWiki warns that a bleed all the way round the cornea, the clear window at the front of the eye, may signal an occult globe rupture, a hidden tear in the wall of the eyeball.

A knock to the eye that is followed by double vision or a sunken-looking eye can be a broken eye socket; that is covered in my article on orbital fractures after a knock to the eye. If the red eye comes with bruising elsewhere, in both eyes, and you have not been hurt, the page on bruising around the eye with no injury is the relevant one.

What if it keeps coming back, or I take blood thinners?

Then it deserves a proper review, not alarm. The AAO advises that frequent subconjunctival haemorrhages should be tested further by an ophthalmologist, and StatPearls says recurrence or accompanying symptoms need investigation to exclude systemic disease or a structural problem.

A sensible review usually looks at a few things:

• Blood pressure, because high pressure is a main association in older adults.
• Diabetes, which the AAO and StatPearls both list as a risk.
• Medicines that thin the blood: aspirin, antiplatelet drugs and anticoagulants. EyeWiki advises checking that warfarin control is not above its target range.
• A bleeding tendency, where EyeWiki lists blood disorders and severe liver disease, and a clotting check may be requested when the history points that way.
• The eye itself, to confirm the patch is only a bleed and the surface underneath is normal.

Here is the honest complication. A repeated red patch in an older adult who takes a blood thinner can be an expected side effect, or a sign that the dose or the blood level needs checking. The drug may be protecting that person from a stroke or a clot, and stopping it alone could do far more harm than a red eye ever will. The right step is a conversation with the doctor who prescribed it, and it is the prescriber, not the eye, who decides whether anything changes. I would rather you came with the question than made the change yourself.

When should I see a doctor the same day?

The same day if the eye is painful, if light hurts, if your vision is dim or blurred, if there is discharge, or if the bleed followed a real injury. The NHS adds that any change to your sight, such as wavy lines, flashing or loss of vision, an injury, a chemical splash, a severe headache with feeling sick, or one pupil larger than the other needs emergency care at once.

An appointment within a few days is reasonable if the patch is still bright and unchanged after about two weeks, if it keeps coming back, if both eyes are involved, or if you simply want it checked. The NHS suggests seeing a GP or optician if red patches in the eye last for more than a few days or you are worried.

For children, the question is different, and Little Eyes 101 has written a separate page on a red patch on the white of a child's eye. If you are unsure which kind of doctor to start with, see what an oculoplastic surgeon does, and for the wider map, the eye socket and thyroid section and my hub article on why eyes look tired.