Eye problems: a structured approach
Four stop checks, visual acuity in every eye, four sorting questions, then examine from the outside in.
A 62-year-old woman has a painful red left eye, blurred vision with rainbow haloes around lights, headache and vomiting since last evening. The left pupil is mid-dilated and doesn't react; the eye feels hard to gentle pressure through the lid.
A 70-year-old man suddenly lost vision in his right eye 2 hours ago, painlessly, "like a curtain coming down". He has AF and isn't anticoagulated.
What are these, and how urgent is each?
- Stop checks firstChemical injury, penetrating injury, sudden vision loss, possible giant cell arteritis.
- Visual acuityEvery patient, each eye separately, with glasses or pinhole.
- Red, painful eye with reduced visionSame-day eye review.
- Sudden painless loss of visionRetinal artery or vein occlusion, detachment, vitreous haemorrhage, GCA: same day.
- Look at the pupilFixed mid-dilated: acute glaucoma. Relative afferent defect: optic nerve or retina.
- Flashes, floaters, curtainRetinal detachment: same day.
- Mild red eye, normal visionUsually conjunctivitis. See the red eye guide.
- Sudden loss of vision
- Painful red eye with reduced vision
- Chemical or penetrating injury
- Flashes and curtain
- Headache with jaw pain over 50
- Double vision with headache or a painful third nerve palsy
- Acute angle-closure glaucoma
- Giant cell arteritis
- Retinal detachment
- Central retinal artery occlusion (stroke equivalent)
- Microbial keratitis
- Pituitary tumour (bitemporal field loss)
- Third nerve palsy from aneurysm
| Acute angle-closure glaucoma | Painful red eye, haloes, vomiting, fixed mid-dilated pupil, hard eye: emergency |
| Retinal detachment | Flashes, floaters, shadow or curtain: same day |
| Central retinal artery occlusion | Sudden painless severe loss, cherry-red spot: immediate, treat as a stroke |
| Over 50 with headache and visual loss | GCA: ESR, CRP, high-dose steroids today |
| Contact lens wearer with painful red eye | Keratitis until proven otherwise |
| Visual acuity | 6/6 normal, pinhole improves refractive error |
Check every dose against a current drug reference and your hospital protocol.
On this page
Always measure visual acuity
- Each eye separately, with distance glasses on, using a Snellen chart at 6 metres (or a near chart).
- If worse than 6/12, try a pinhole: improvement means a refractive problem.
- If they can't read the chart: count fingers, hand movements, light perception.
- Visual acuity is the vital sign of the eye. Record it before anything else (except chemical irrigation).
Red flags
- VVision reducedMeasure acuity every time
- PPain (not just grittiness)Keratitis, uveitis, glaucoma, scleritis
- PPupil abnormalFixed, mid-dilated or irregular
- PPhotophobiaUveitis, keratitis
- CContact lens wearerKeratitis risk
- TTrauma or chemicalIrrigate, shield
Sudden loss of vision
- Acute angle-closure glaucoma
- emergency eye referral
- Giant cell arteritis
- steroids today, ESR and CRP
- Optic neuritis
- eye or neurology
- Central retinal artery occlusion
- immediate eye referral, stroke work-up
- Retinal detachment
- same day
- Vitreous haemorrhage
- eye team
Acute angle-closure glaucoma
- Older, long-sighted people, more often women; triggered by dim light or dilating drops.
- Painful red eye, blurred vision, haloes around lights, headache, nausea and vomiting, cloudy cornea, fixed mid-dilated pupil, hard eye.
- Emergency: eye team immediately. While waiting, per local protocol: lie flat, analgesia, antiemetic, IV or oral acetazolamide, and pressure-lowering drops as directed by the eye team.
- Often misdiagnosed as migraine or gastroenteritis because of headache and vomiting. Always look at the eye.
Central retinal artery occlusion
- Sudden painless loss of vision in one eye, often severe (counting fingers or worse), relative afferent pupil defect, pale retina with a cherry-red spot.
- An eye stroke: refer immediately to the eye team, and arrange stroke work-up (ECG for AF, carotids, BP, lipids, glucose). Check ESR and CRP for GCA in over 50s.
Gradual loss of vision
| Cause | Clues |
|---|---|
| Cataract | Slow blur, glare, common with age and diabetes |
| Diabetic retinopathy | Diabetes; screening matters |
| Chronic glaucoma | Painless, peripheral field loss, family history |
| Macular degeneration | Central blur, distortion, elderly |
| Refractive error | Improves with pinhole |
| Pituitary tumour | Bitemporal field loss, headaches |
Investigations
| Test | Why |
|---|---|
| Visual acuity | Every patient |
| Pupils | Relative afferent defect, fixed pupil |
| Fluorescein | Corneal damage |
| Fundoscopy | Papilloedema, retinal changes |
| Visual fields to confrontation | Field defects |
| ESR, CRP | GCA in over 50s |
| Glucose, BP | Diabetic and hypertensive eye disease |
| Intraocular pressure (eye team) | Glaucoma |
Treatment
Common mistakes
- Not measuring visual acuity.
- Calling acute glaucoma "migraine" or "gastroenteritis".
- Missing GCA in an older person with headache and blurred vision.
- Treating sudden painless visual loss as non-urgent.
- Using steroid drops without an eye specialist.
- Missing a bitemporal field defect.
Frequently asked questions
What are the symptoms of acute angle-closure glaucoma?
A painful red eye, blurred vision with haloes, headache, nausea and vomiting, a fixed mid-dilated pupil and a hard eye. It is an emergency.
What should be checked in every eye problem?
Visual acuity in each eye, with glasses or a pinhole.
What causes sudden painless loss of vision?
Central retinal artery or vein occlusion, retinal detachment, vitreous haemorrhage, and giant cell arteritis in older people.
What is a cherry-red spot?
The appearance of the macula in central retinal artery occlusion: a pale, swollen retina with a red centre. It needs immediate referral.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. A 62-year-old has a painful red eye, haloes, vomiting and a fixed mid-dilated pupil. What is the diagnosis?
Answer: Acute angle-closure glaucoma. Emergency: lower pressure and refer to the eye team immediately.
- Migraine: Eye signs point to glaucoma.
- Subconjunctival haemorrhage: Painless.
- Conjunctivitis: No pupil change.
- Uveitis: Small pupil.
2. A patient sees flashes and floaters and then a curtain over part of one eye. What is suspected?
Answer: Retinal detachment. Same-day eye referral for retinal detachment.
- Cataract: Gradual.
- Conjunctivitis: No.
- Migraine aura: Bilateral and resolves.
- Glaucoma: Different.
3. What should be measured in every patient with an eye complaint?
Answer: Visual acuity. Visual acuity in each eye is the vital sign of the eye.
- Colour vision: Not always.
- Intraocular pressure: Not always available.
- Blood sugar: Not always.
- Corneal thickness: No.
4. A 58-year-old short-sighted man has had flashing lights and new floaters in his left eye for 2 days. Today a dark shadow is spreading across his vision from below, "like a curtain". What is the diagnosis and urgency?
Answer: Retinal detachment — same-day referral. Flashes (retinal traction) and floaters followed by a progressive curtain or shadow suggest rhegmatogenous retinal detachment. Myopia, older age, trauma and cataract surgery increase the risk. Same-day ophthalmology review is needed; surgery is most urgent while the macula is still attached ("macula-on"), to preserve central vision.
- PVD only — routine review: A curtain means the retina has probably detached; this is urgent.
- Migraine aura — analgesia: Aura is bilateral, lasts under an hour and causes no curtain.
- Vitreous haemorrhage — observe at home: Vitreous haemorrhage causes sudden floaters, but a spreading curtain means detachment needing urgent referral.
5. A long-sighted 65-year-old woman develops a painful red eye, haloes and vomiting a few hours after starting a new drug. Which drug is most likely to have triggered acute angle-closure?
Answer: Oxybutynin. Drugs that dilate the pupil can precipitate acute angle-closure in eyes with narrow angles (hypermetropia, older age, women, East/South Asian ethnicity): anticholinergics (oxybutynin, atropine, hyoscine, ipratropium nebulised, tricyclics, antihistamines, antipsychotics), sympathomimetics (adrenaline, phenylephrine drops, salbutamol nebulised), mydriatic drops (tropicamide). Topiramate (and sulfonamides) cause bilateral angle closure by ciliary body swelling — not pupil block. Glaucoma drugs: prostaglandin analogues (latanoprost — ↑ uveoscleral outflow; iris darkening, lash growth), beta-blockers (timolol — ↓ aqueous; avoid in asthma/heart block), alpha-2 agonists (brimonidine), carbonic anhydrase inhibitors (dorzolamide, acetazolamide), miotics (pilocarpine — opens the angle).
- Pilocarpine: Pilocarpine constricts the pupil and treats angle closure.
- Timolol: Timolol lowers eye pressure and does not dilate the pupil.
- Topiramate: Causes angle closure by ciliary effusion, usually after weeks.
6. Which structure passes superficial to the flexor retinaculum at the wrist?
Answer: Ulnar nerve. Structures superficial to the flexor retinaculum: the ulnar nerve and artery (in Guyon's canal), the palmaris longus tendon, and the palmar cutaneous branches of the median and ulnar nerves. The median nerve and flexor tendons pass through the carpal tunnel beneath it.
- Median nerve: Passes through the carpal tunnel.
- Flexor pollicis longus tendon: Passes through the carpal tunnel.
- Flexor digitorum profundus tendons: Pass through the carpal tunnel.
- Flexor digitorum superficialis tendons: Pass through the carpal tunnel.
7. A man suddenly loses vision in one eye; fundoscopy shows a pale retina with a cherry-red spot at the macula. Which artery is blocked?
Answer: Central retinal artery. The central retinal artery (an end artery from the ophthalmic artery) supplies the inner retina; the outer retina (rods and cones) is nourished by the choroid (short posterior ciliary arteries). Occlusion (often embolic from carotid plaque) causes sudden painless monocular blindness, pale oedematous retina and a cherry-red spot where the thin fovea shows the intact choroid beneath. Giant cell arteritis must be excluded in the elderly.
- Posterior cerebral artery: Visual field defect, not monocular loss.
- Middle cerebral artery: Field loss, hemiparesis.
- Short posterior ciliary arteries: Ischaemic optic neuropathy.
- Anterior ciliary artery: Anterior segment.
References and dose sources
- College of Optometrists: bacterial
- College of Optometrists: viral
- NHS Scotland: ophthalmia neonatorum
- College of Optometrists: allergic
- NHS Scotland: acute allergic
- College of Optometrists
- College of Optometrists
- NHS Scotland
- NHS Scotland: acute angle closure
- College of Optometrists: angle closure
- Acetazolamide dosing: Drugs.com: Acetazolamide dosage (see also our acetazolamide dose page)
- Prednisolone dosing: Drugs.com: Prednisolone dosage (see also our prednisolone dose page)
- Ondansetron dosing: Drugs.com: Ondansetron dosage (see also our ondansetron dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.