Eye presentations are common in primary care, but a small number represent true ophthalmic emergencies where delayed recognition can lead to permanent sight loss, neurological injury, or even death. For GP trainees and AKT candidates, the challenge is not diagnosing rare eye conditions, but rapidly identifying red‑flag features that require urgent or same‑day specialist referral.

The RCGP AKT, NICE guidance, and British Thoracic Society / Royal College–endorsed ophthalmology pathways consistently emphasise the same principle:

Most eye conditions are benign — but the few that are dangerous must not be missed.

Red Flag	Clinical Significance / Concern	Key Diagnostic Features	Referral Action
Sudden painless visual loss	CRAO/BRAO, retinal detachment, vitreous haemorrhage; stroke equivalent	Cherry-red spot (CRAO), hemifield shadow, sudden floaters ± flashes	🔴 Same-day emergency referral; initiate stroke protocol if CRAO suspected
Sudden painful visual loss	AAG, optic neuritis, anterior uveitis, keratitis	Mid-dilated pupil, corneal haze, ↑ IOP, photophobia, ciliary flush	🔴 Same-day ophthalmology referral
RAPD	Optic nerve or retinal pathology; not caused by cataracts	Swinging light test positive; asymmetric light response	⚠️ Urgent (next-day) referral
Flashes + floaters ± visual field loss	Retinal detachment or tear (sight-threatening)	Photopsia, shadow/curtain in field, ↑ floaters	🔴 Same-day referral if visual field affected
Haloes + red eye + nausea	Classic for acute angle-closure glaucoma	Unilateral headache, nausea, red eye, mid-dilated pupil	🔴 Emergency same-day referral
New-onset binocular diplopia	Cranial nerve palsy, stroke, aneurysm	CN III signs: ptosis, "down and out" eye, dilated pupil	🔴 Same-day referral + urgent neuroimaging if pupil involved
Corneal ulcer / central opacity	Infectious keratitis (esp. contact lens wearers)	Pain, photophobia, fluorescein stain, corneal infiltrate	🔴 Same-day urgent referral; avoid topical steroids
Ocular trauma / chemical burn	Globe rupture or chemical injury	Hyphema, chemosis, subconjunctival haemorrhage, alkali/acid burn	🔴 Emergency referral; irrigate immediately for chemical injury
Painful proptosis / visual loss	Orbital cellulitis, mass, thyroid eye disease	Proptosis, fever, pain with movement, decreased vision	🔴 Same-day referral + orbital imaging
Photophobia with red eye	Anterior uveitis, keratitis	Photophobia, watery discharge, ciliary flush	🔴 Same-day referral
Eye pain + headache + vision loss	Temporal arteritis or AAG	Age >50, jaw claudication, ESR/CRP ↑, scalp tenderness	🔴 Same-day referral; consider steroids if GCA suspected
Ptosis + diplopia ± pupil involvement	CN III palsy; possible aneurysm	"Down & out" eye, dilated pupil, ptosis	🔴 Same-day emergency referral + neuroimaging
Red eye + reduced VA (contact lens wearer)	Microbial keratitis	Central corneal infiltrate, photophobia, discharge	🔴 Same-day emergency referral
Unilateral conjunctival injection + ↓ VA	Possible AAG, uveitis, scleritis	Ciliary injection, severe pain, photophobia	🔴 Same-day referral if red flags present

NICE "Red Eye" Clinical Knowledge Summary (2012) – 5 Must-Document Features:

Always record in any eye assessment:

• Visual acuity (Snellen or equivalent)

• Pain – quantify severity

• Photophobia

• Discharge – amount/type

• Trauma history and laterality (unilateral vs bilateral)

Same-Day Emergency Referrals Required For:

• ↓ Visual acuity + ANY eye pain or photophobia

• Severe pain ± photophobia (with or without ↓ colour vision)

• Suspected corneal ulcer / keratitis

• Ocular trauma, chemical injury, or high-velocity injury

• Contact lens wearers with red eye (exclude pseudomonas ulcer)

• AAG triad: haloes + nausea/vomiting + red painful eye

• Sudden painless vision loss (e.g. CRAO — stroke equivalent)

• Flashes + floaters + visual field loss (retinal detachment)

• Cranial nerve palsy + diplopia (esp. CN III — aneurysm risk)

❌ Do NOT Use Topical Steroids in Primary Care:

• Suspected keratitis, uveitis, or scleritis

• Contact lens–related infections (↑ risk of HSV/herpes simplex keratitis)

🚫 Always refer to ophthalmology first; steroids can worsen outcomes if misused.

BP-Lowering / Dilation Cautions in AAG:

• Do NOT dilate pupils (e.g. mydriatic drops) if acute angle-closure glaucoma is suspected

• Avoid cycloplegics and agents that raise intraocular pressure.

References

1. Imperial NHS Trust (2024) – The Red Eye and referral patterns. Primary care ophthalmology study file documenting NICE red flag assessment framework (visual acuity, pain, photophobia, discharge, trauma)

2. BMJ Rapid Response (2011) – Angle closure Glaucoma: 'Red flag' disease. Clinical review highlighting haloes + nausea + pain as classic acute angle-closure glaucoma triad requiring emergency referral

3. NHS Greater Glasgow & Clyde (2025) – A Closed-Loop Audit: The Assessment of Red Flags. Quality improvement audit evaluating ophthalmic red flag recognition and referral patterns in primary care

4. Dr. Parth Shah (2025) – Red flags for red eyes: Understanding acute angle closure glaucoma. Specialist ophthalmology blog detailing diagnostic features (mid-dilated fixed pupil, corneal haze, IOP 50-80 mmHg) and emergency management

5. StatPearls (2023) – Acute Angle-Closure Glaucoma. NCBI Bookshelf clinical overview of AAG pathophysiology, presentation, and contraindication to mydriatics in acute setting

6. Eye News UK (2025) – My Top Five: Red flag presentations all resident doctors must know. Educational review covering CRAO stroke-equivalent timeline (12-15 minutes), retinal detachment field loss, and CN III palsy aneurysm risk

7. BMJ Open Quality (2016) – Red eyes and red-flags: improving ophthalmic assessment and referral in primary care. Primary care audit defining NICE 5-element red flag assessment (VA, pain, photophobia, discharge, trauma)

8. Healthline (2024) – Retinal Artery Occlusion: Symptoms, Causes, and Treatment. Patient education resource documenting sudden painless vision loss, cherry-red spot, and cardiovascular risk association

9. RACGP (2014) – Flashes and floaters: a practical approach to assessment. Australian GP guidance on posterior vitreous detachment vs retinal tear/detachment differentiation

10. Barraquer (2024) – Symptoms of retinal detachment. Specialist ophthalmology center outlining peripheral photopsias, curtain/shadow over visual field as detachment indicators

11. StatPearls (2024) – Central Retinal Artery Occlusion. NCBI Bookshelf detailing CRAO as stroke-equivalent requiring immediate intervention within 12-15 minute window

12. Dr. Agarwal (2025) – Retinal Detachment. Educational material on sudden floaters increase and peripheral field loss as emergency indicators

13. Michigan Kellogg Eye Center – Flashes. University ophthalmology department guidance on retinal detachment warning signs

14. EyeRounds (2004) – Chapter 9. Glaucoma emergency: Acute angle closure. University of Iowa ophthalmology education resource on AAG presentation and management

15. PMC Article (2021) – Acute Closed-Angle Glaucoma—An Ophthalmological Emergency. Specialist review emphasizing emergency nature and treatment timeline

16. Eye Wiki (2025) – Retinal Artery Occlusion. Collaborative ophthalmology knowledge base documenting irreversible retinal damage timeline