Subconjunctival haemorrhage; a cause of red eye explained

A visual representation of a subconjunctival haemorrhage where the eye appears red. The man is pulling his eyelid down gently to show the problematic eye

Imagine looking in the mirror one morning and noticing the white of your eye had turned a startling red.

If this has ever happened to you, it’s likely you’ve experienced a subconjunctival haemorrhage, a common, painless but dramatic-looking eye condition. Fortunately, while it may look concerning, most cases are harmless and resolve on their own without treatment.

A visual representation of a subconjunctival haemorrhage where the eye appears red. The women is using her hands to hold the eye open for a better look

What Is a Subconjunctival Haemorrhage?

A subconjunctival haemorrhage occurs when a tiny blood vessel bursts within the conjunctiva, the clear surface layer of the eye. This leads to a bright red or dark patch appearing in the sclera, or the white part of the eye. The conjunctiva can’t quickly absorb the blood, so it becomes trapped, creating a vivid red.

A visual representation of a man with subconjunctival haemorrhage where the eye appears red.

Why Do Subconjunctival Haemorrhages Happen?

These small blood vessel breaks can occur for various reasons, often with no clear cause. Sometimes, simple actions like coughing, sneezing, heavy lifting, or straining can increase pressure in the blood vessels, causing one to rupture. Even rubbing your eyes too hard can occasionally trigger it.

Other times, certain health factors make someone more prone to subconjunctival haemorrhages, such as:

Blood thinners: People taking anticoagulants, like warfarin or aspirin, have a higher risk because these medications can make the blood more likely to leak from vessels.
High blood pressure: Although not a direct cause, high blood pressure can put extra strain on blood vessels and may increase the risk of subconjunctival haemorrhages.

Should I Be Worried?

In most cases, a subconjunctival haemorrhage is harmless. It may look dramatic but typically doesn’t affect vision, cause pain, or signal a serious underlying issue. The red patch usually clears up on its own within one to two weeks, similar to how a bruise fades on the skin.

However, it’s worth keeping an eye (no pun intended) on a few factors:

If it happens repeatedly: Although occasional cases are normally benign, recurrent subconjunctival haemorrhages may warrant further investigation. Recurrent episodes can sometimes indicate an underlying issue, such as high blood pressure or a blood clotting disorder.
People on blood thinners: If you’re on blood-thinning medications and experience recurrent haemorrhages, it’s a good idea to discuss this with your healthcare provider. They may recommend blood tests or adjustments to your medication dosage.
Unusual symptoms: If you experience pain, vision changes, or if the redness is associated with other symptoms consult an eye specialist or your general practitioner, as this could indicate a more serious condition.

Someone with a blood pressure machine, reading their results

A visual representation of a subconjunctival haemorrhage where the eye appears red.

What Can Be Done?

For most people, no treatment is required for a subconjunctival haemorrhage; it simply resolves on its own. However, here are some tips to make the healing process a bit easier:

Avoid rubbing your eyes: This can help prevent further irritation or worsening of the haemorrhage.
Use artificial tears: If your eye feels dry or irritated, lubricating eye drops can help relieve any mild discomfort.
Monitor your blood pressure: Since high blood pressure can sometimes contribute to subconjunctival haemorrhages, regular monitoring can be helpful, especially if you’re prone to these.

The Bottom Line

Waking up with a subconjunctival haemorrhage can be an unsettling experience, but in most cases, it’s not a cause for concern. The redness may be striking, but these small blood vessel breaks are typically harmless and resolve on their own within a couple of weeks. However, if you experience frequent occurrences, are on blood thinners, or notice other unusual symptoms, a quick check-in with your healthcare provider can provide peace of mind and rule out any underlying issues.

With a little patience, that dramatic red patch will soon fade, leaving your eye looking as clear as ever.

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