Reasoning GP · Algorithm · 1-page summary
Red eye — acute presentation
For: acute red eye in general practice, face to face or remote. Not for: neonates — ophthalmia neonatorum → Same-day paediatric ophthalmology, swab urgently.
Core rule: pain + reduced vision = sight-threatening: never call it conjunctivitis — refer same day. Irrigate a chemical injury before anything else.
0Stop — call 999 now — do not delay for examination
- Chemical splash (acid or alkali) → irrigate at once and continuously until ocular-surface pH is neutral; remove lenses and particles; do not delay for history or VA → emergency ophthalmology, 999 if severe.
- Acute angle closure: severe unilateral pain, haloes, vomiting, cloudy cornea, fixed mid-dilated pupil → 999 / immediate ophthalmology. Do not delay for tonometry.
- Open globe (grinding, hammering, teardrop pupil); sudden severe visual loss; hyphaema with visual compromise or high IOP; orbital cellulitis with systemic illness, proptosis, ophthalmoplegia or neurology → 999
- While waiting: rigid shield without pressure; do not patch tightly, palpate the globe or remove an embedded foreign body. No IV acetazolamide from routine primary care.
1Triage — pain, vision, contact lenses
| Finding | Action |
|---|---|
| Painful | With photophobia, ciliary flush or abnormal pupil → Same-day eye unit |
| Reduced VA | Not explained by discharge or refractive blur → Same-day eye casualty |
| Contact lenses | Painful, photophobic or blurred → Same-day. Mild → prompt review. Lenses out. |
| Diplopia, RAPD | Urgent assessment |
| Painless, VA normal | → blocks 3 and 4 |
2Screen — one row is enough
- Keratitis / corneal ulcer: pain, photophobia, white opacity or fluorescein staining → Same-day ophthalmology; do not patch.
- Anterior uveitis: ciliary flush, photophobia, deep ache, small irregular pupil → Same-day ophthalmology
- Scleritis: severe deep boring pain, does not blanch → Same-day ophthalmology
- HSV dendrite, or HZO with V1 vesicles or ocular symptoms → Same-day ophthalmology; antiviral when indicated must not delay it.
- Gonococcal: hyperpurulent, chemosis → Same-day ophthalmology + GUM
- Hyphaema; recent eye surgery or injection with pain, redness or reduced VA; stuck foreign body or rust ring → Same-day ophthalmology
3Assess — once blocks 0–2 are answered
☐ VA first, each eye, with pinhole ☐ Pupils ☐ Injection pattern ☐ Fluorescein ☐ Lid eversion ☐ Nodes, discharge ☐ Eye movements ☐ BP if subconjunctival haemorrhage
Not in primary care: palpating the globe for IOP; routine swabs, bloods, imaging. Swab only if gonococcal, resistant after 7 days, neonatal or immunocompromised.
4Classify — only if the screen is negative
- Bacterial conjunctivitis — mucopurulent, lids stuck → many resolve in 5–14 days.
- Viral — watery, pre-auricular node, recent URTI → 2–3 weeks. Allergic — bilateral itch, atopy.
- Subconjunctival haemorrhage — painless, sharply demarcated → reassure; check BP.
- Episcleritis — sectoral, mild, blanches with phenylephrine 2.5%; if not → think scleritis.
- Blepharitis — lid crusting, worse mornings. Dry eye — gritty, worse evenings.
- Uncertain — say so → community optometry, eye casualty or ophthalmology; never manage it remotely.
5Treat today — benign causes only; doses: NICE/SPC, BNF, local formulary
- Bacterial: hygiene; mild often needs no or a delayed antibiotic; if appropriate, chloramphenicol per local formulary.
- Allergic: sodium cromoglicate 2% four times daily; inadequate → olopatadine 0.1% twice daily. Viral: lubricants, cold compresses.
- Blepharitis: warm compresses, lid massage and cleaning, long term. Dry eye: lubricants; benefit takes 4–6 weeks.
- Lenses: stop until resolved + 24 h after antibiotics. Anticoagulant: check INR if relevant; do not stop reflexively.
6Refer routinely
- Blepharitis or dry eye failing after 3 months → ophthalmology.
- Recurrent or painful episcleritis → ophthalmology advice.
- Subconjunctival haemorrhage 2+ in 6 months → FBC, clotting, BP.
- Chronic follicular conjunctivitis + sexual exposure → GUM (chlamydia). Allergic not working → review at 4 weeks.
7Never reassure by
- Normal VA — it does not exclude uveitis or early keratitis.
- No discharge — it does not exclude serious eye disease.
- A "conjunctivitis" label for a painful eye with reduced acuity.
- Mild symptoms in a contact-lens wearer.
- Steroid drops for an undiagnosed red eye.
- A remote assessment of an undiagnosed red eye.
8Safety-net — say it, then document it
999 “Sudden severe eye pain with haloes or sickness, sudden loss of vision, an injury at speed — call 999. Chemical splash: wash with water continuously first.” Same day: “Vision drops, the eye turns painful or light-sensitive (lens wearers: take lenses out), a white spot, heavy pus, a forehead or nose rash, or worse despite treatment — contact the eye unit today.”
Remote or OOH: no fluorescein or VA testing and uncertain → optometry, eye casualty or ophthalmology. Infective: own towels; exclusion per UKHSA advice.
✓Safe to leave primary care only if — all five, documented
No block 0–2 row applies
VA normal each eye; pupils and fluorescein normal
One benign cause explains it, or uncertainty stated
No steroid drops; lenses out; review set
Safety-net given and documented
Summary of the full Reasoning GP red eye algorithm, which holds the detail, examination, treatments and evidence. Sources: Royal College of Ophthalmologists emergency eye care (2024); NICE NG81, NG136, NG203; BASHH; College of Optometrists Clinical Management Guidelines; UKHSA; CoSRH CEU. Clinical reference — follow local eye pathways and check doses: NICE/SPC, BNF.