A red or bloodshot eye is one of the most common reasons people present to an eye clinic or A&E. The vast majority of cases are benign — a burst blood vessel, a minor infection, or dryness. But a small number represent genuine emergencies where delayed treatment can cause permanent vision loss. The key is knowing which is which.
Common, non-urgent causes
- Subconjunctival haemorrhage — a bright red patch caused by a tiny burst blood vessel on the surface of the eye. Looks alarming but is almost always harmless and resolves in 1–3 weeks without treatment. Often occurs after coughing, sneezing, or straining.
- Conjunctivitis (bacterial or viral) — pink or red eye with discharge and mild discomfort. Usually resolves on its own; bacterial conjunctivitis responds to antibiotic drops.
- Allergic conjunctivitis — redness, itching and watering, usually both eyes, triggered by pollen, dust mites or pet dander. Antihistamine drops help.
- Dry eye disease — chronic low-grade redness, grittiness and fluctuating blur. Very common, especially in older patients and screen users.
- Contact lens-related redness — wear time or lens fit issues. Always remove lenses before attending any eye appointment.
Red eye signs that need urgent assessment today
The following combinations require same-day or emergency ophthalmic assessment. Do not wait for a routine GP appointment.
- Red eye + significant pain or ache around the eye — could indicate acute angle-closure glaucoma or uveitis (iritis).
- Red eye + reduced vision — any measurable drop in clarity is a red flag.
- Red eye + sensitivity to light (photophobia) — typical of uveitis, keratitis, or acute glaucoma.
- Red eye + seeing halos around lights — a classic symptom of elevated intraocular pressure in acute glaucoma.
- Red eye after an injury or foreign body — especially if there is any chance of a penetrating injury. Do not rub the eye.
- Red eye in a contact lens wearer with pain and blur — urgent: could be microbial keratitis (corneal ulcer), which can scar rapidly.
Acute angle-closure glaucoma — the eye emergency most people miss
Acute angle-closure glaucoma is the condition that catches people out most often, because it can mimic a headache or even a migraine. The intraocular pressure rises suddenly and dramatically, causing a red, hazy-looking eye, severe pain, nausea, vomiting, and halos around lights.
It is a true ophthalmic emergency. Without treatment within hours, permanent optic nerve damage occurs. If you or someone you know has this combination of symptoms, call 999 or go directly to A&E.
Uveitis (iritis) — the silent inflammatory red eye
Uveitis is inflammation inside the eye. It typically presents as a painful, red eye with a small or irregular pupil, blurred vision and photophobia. Unlike conjunctivitis, there is usually minimal discharge. It can be associated with systemic conditions such as ankylosing spondylitis, sarcoidosis, or inflammatory bowel disease, but is often idiopathic.
Treatment involves steroid eye drops to reduce inflammation and dilating drops to prevent the iris sticking to the lens. Early treatment prevents complications including raised pressure, cataract, and macular oedema.
What to do
- No pain, normal vision, no recent injury: see your GP or optician within a day or two.
- Mild discomfort but vision is normal: call an optician for a same-day appointment.
- Pain, reduced vision, photophobia, or halos: go to your local eye casualty or A&E today. In West Yorkshire: Huddersfield Royal Infirmary Eye Casualty.
- Suspected penetrating injury: call 999.
Frequently Asked Questions
Is a completely red eye (subconjunctival haemorrhage) dangerous?
A bright red patch on the white of the eye — a subconjunctival haemorrhage — looks alarming but is almost always harmless. It is caused by a tiny blood vessel bursting on the surface (not inside) the eye. Vision is unaffected and it resolves over 1–3 weeks. If it recurs frequently, a blood pressure check is worthwhile. If it is associated with pain or reduced vision, seek urgent review.
Can pink eye (conjunctivitis) cause permanent damage?
Simple viral or bacterial conjunctivitis very rarely causes lasting damage. However, certain types of infective keratitis (corneal infection) — which can superficially resemble conjunctivitis — can scar the cornea if untreated. Any red eye with significant pain or reduced vision in a contact lens wearer needs urgent assessment.
My eye has been red for weeks with no other symptoms. Should I worry?
Chronic, low-grade redness without pain or vision change is most commonly dry eye disease, blepharitis (lid margin inflammation), or mild allergic conjunctivitis. It is worth seeing an optician or GP to confirm. If artificial tears and basic lid hygiene do not help within a month, a consultant ophthalmology opinion is appropriate.
Mr Mohamed Mohyudin
MBChB BSc MSc FRCOphth CCT — Consultant Ophthalmic Surgeon, Spire Elland Hospital, Yorkshire. GMC 7039600.
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