A Red Eye: Which Ones Settle, and Which Need Seeing Today

Nearly every red eye gets the same treatment at home — a pharmacy drop and a few days’ patience. Most of the time that is fine. What almost nobody is told is how to spot the small number that are not fine, and those are the ones that cost vision.

So here is the practical version.

Redness alone tells you very little

The white of the eye reddens whenever its surface blood vessels widen. Dust, smoke, a late night, a swimming pool, an allergy or an infection will all do it.

So redness on its own is not the useful signal. What matters is the company it keeps: pain, vision change, light sensitivity and the shape of the pupil. Those are what separate an irritated eye from a threatened one.

The signs that mean go today

Treat a red eye as urgent if any of these are present:

• Real pain, rather than grittiness or itching — a deep ache is different from irritation
• Blurred or reduced vision that does not clear when you blink
• Strong sensitivity to light, enough that you want to keep the eye shut
• A pupil that looks different in size or shape from the other eye
• Halos around lights, with a red eye and a headache or nausea
• Something struck or entered the eye, including chemicals, grinding sparks or a plant scratch
• You wear contact lenses and the eye has become red and painful
• The redness sits in one patch against a background of pain and light sensitivity

Contact lens wearers deserve a lower threshold than everyone else. A red, painful eye in a lens wearer can be a corneal infection, and those move quickly.

For a chemical splash, do not wait for anything: rinse the eye with clean running water for fifteen to twenty minutes, then go straight to eye casualty.

The ones that usually settle

Conjunctivitis. Redness across the whole white of the eye, gritty rather than painful, often with discharge and frequently both eyes. Viral cases settle on their own; hygiene matters because it spreads easily.

Allergy. Itching is the giveaway — allergic eyes itch in a way infected eyes do not. Often seasonal, usually both eyes, often with sneezing.

Dry eye. Burning, fluctuating vision that clears on blinking, worse with screens, air conditioning and fans.

A subconjunctival haemorrhage. A dramatic patch of solid red, like a bruise on the white of the eye. It looks alarming and is usually harmless, with no pain and no vision change. It clears over a couple of weeks.

Tiredness, smoke or dust. Ordinary, and settles with rest and time.

Why the pharmacy drop is not always neutral

Redness-relief drops work by narrowing the blood vessels. They do not treat a cause, and used regularly they produce rebound redness that is worse than the original.

More importantly, steroid drops used without an examination can turn a herpes infection of the cornea into a serious one, and can raise eye pressure. That is why a red eye that is painful or affecting vision should be examined before anything is put into it.

If a drop has been prescribed for you before, that does not make it right for the next red eye. Different causes, different treatments.

What the examination involves

An eye examination for a red eye is quick and painless. Vision is measured first, then the eye is examined at the slit lamp under magnification.

A drop of orange dye is often used: it shows up scratches or ulcers on the cornea under blue light, which is how a minor abrasion is separated from an infection. Eye pressure is measured where the picture suggests it matters.

Most people leave with a clear cause and the right treatment within half an hour.

The takeaway

A red, gritty, itchy eye with normal vision and no real pain can usually wait, and often needs nothing.

A red eye with pain, reduced vision, light sensitivity or an odd-looking pupil should be seen the same day — and so should any red eye in a contact lens wearer. In fact, those four questions are the whole triage: does it hurt, can you see, does light bother you, and does the pupil look right.

Mount Lotus Eye & ENT Hospital — Mount Lavinia & Kurunegala. Eye casualty and consultant eye surgeons, open daily 7am–8pm.
📞 Mount Lavinia: 0112 333 444 | Kurunegala: 0372 333 444