Eye pain: causes, red flags and when to get urgent help

Doctors divide eye pain by where it seems to start. Surface pain feels gritty, scratchy, burning or stinging and sits in the lids, conjunctiva or cornea. Deep pain is a dull ache or throb inside or behind the eye and suggests inflammation or raised pressure within the eye. Referred pain feels like eye pain but comes from the head, sinuses or nerves, as happens with migraine and cluster headache.

The accompanying features matter more than the pain itself. A red eye, sensitivity to light, blurred vision, haloes, nausea, a headache, discharge or a history of injury, eye surgery or contact lens wear narrow the possibilities quickly.

The NHS describes dry eyes as itchy, sore, gritty, red, blurry, sensitive to light or more watery than normal, and not usually serious. It lists risk factors as being over 50, wearing contact lenses, long periods looking at screens without a break, air-conditioned or heated environments, wind and dust, smoking, alcohol, certain medicines such as some antidepressants or blood pressure medicines, and conditions including blepharitis, Sjögren's syndrome or lupus.

Conjunctivitis, also called red or pink eye, makes eyes red, burning or gritty, with pus that sticks to lashes, itching and watering. It usually affects both eyes and clears within a couple of weeks. The NHS says conjunctivitis with sticky pus is contagious, and allergic conjunctivitis is not.

Glaucoma usually has no symptoms and develops slowly, but the NHS says it can sometimes develop suddenly and cause intense eye pain, a red eye, tenderness around the eyes, seeing rainbow-coloured circles around bright lights, blurred vision, nausea and vomiting and a headache. It adds that other conditions, including uveitis and an eye injury, can cause similar symptoms.

Uveitis, also known as iritis, is inflammation inside part of the eye. The NHS lists eye pain that may feel worse when reading, red or watery eyes, reduced or blurred vision, sensitivity to light and flashes or floaters. It usually affects one eye, can develop over hours or over weeks, and in most cases the cause is unknown although autoimmune conditions, some infections and eye injury are known causes. The NHS notes it is important to treat early to avoid long-term complications such as vision loss.

Other causes that clinicians consider include a scratched cornea, a corneal infection (keratitis), scleritis, optic neuritis, shingles around the eye and giant cell arteritis in older adults with a new headache and scalp tenderness.

These thresholds come from the NHS pages on dry eyes, glaucoma, uveitis and conjunctivitis.

• Go to A&E or call 999 if you develop symptoms of glaucoma suddenly: intense pain, a red eye, haloes around lights, blurred vision, nausea or vomiting.

• Go to A&E or call 999 if you cannot see, or lose vision.

• Go to A&E or call 999 if you have any change to your sight such as wavy lines, flashing or loss of vision, if it hurts to look at light, if you have a red eye with severe headache and feel sick, or if your eye is very dark red.

• Go to A&E if you have injured or pierced your eye, or something such as glass or grit is stuck in it. Do not drive yourself.

• Ask for an urgent GP appointment or contact NHS 111 if you have a painful red eye, pain in your eyes with sensitivity to light, very red eyes in one or both eyes, or changes in vision such as flashing or blurring.

• Ask for an urgent GP appointment if you wear contact lenses and your eye is red or painful.

• Get urgent advice for a baby under 30 days old with red, sticky eyes.

An optometrist, GP or eye casualty clinician asks about onset, one or both eyes, vision change, light sensitivity, discharge, contact lens use, previous eye disease or surgery, injury, headaches, jaw pain on chewing and associated rash or illness. Visual acuity is measured, the eye is inspected under magnification, the pupil is checked, and fluorescein drops may be used to show scratches on the cornea.

Eye pressure is measured when glaucoma is suspected, and the NHS notes that glaucoma is usually found during routine eye tests. If a GP thinks you have uveitis the NHS says they will refer you to an ophthalmologist, with follow-up to see whether treatment is working and to check for complications. The NHS suggests having regular eye tests at least every 2 years, and more often if a close relative has glaucoma.

For dry eyes the NHS suggests cleaning eyelids daily with a warm flannel and gentle massage, taking breaks from screens, keeping a computer screen just below eye level, using a humidifier and, if you wear contact lenses, resting your eyes in glasses. It advises not smoking, limiting alcohol, avoiding smoky, dry or dusty places and not stopping prescribed medicines without advice. A pharmacist can suggest eyedrops, gels or ointments.

For conjunctivitis, the NHS suggests wiping the lashes with cooled boiled water on clean cotton wool, a cold flannel on the eyes, not wearing contact lenses until better, washing hands regularly and not sharing towels or pillows. See a GP if symptoms have not cleared within 7 days.