Step 2 CK · Ophthalmology & ENT

Acute Red Eye

Name: Acute Red Eye
Creator: Veli Bakalov, MD

Sort the benign from the sight-threatening in one exam

Ophthalmology & ENT·Urgent Eye Conditions·4 min read·9 high-yield points·Reviewed by Veli Bakalov, MD @HemeOncBuddy

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Same-day ophthalmology red flags: vision loss, severe pain, photophobia, ciliary flush, fixed or mid-dilated pupil, hazy cornea, or a contact-lens wearer.
Conjunctivitis: watery + preauricular node = adenovirus (supportive, contagious 10–14 days); purulent with matted lids = bacterial (erythromycin or trimethoprim-polymyxin); bilateral itch + cobblestone papillae = allergic (olopatadine).
Hyperacute, copious purulent conjunctivitis = Neisseria gonorrhoeae; it can perforate the cornea, so give IM or IV ceftriaxone.
A branching dendritic ulcer on fluorescein = HSV keratitis: topical trifluridine or ganciclovir, or oral acyclovir; never topical steroids alone.
Contact-lens keratitis = Pseudomonas until proven otherwise (stop lenses, fluoroquinolone or fortified drops, urgent referral); Acanthamoeba = water exposure, pain out of proportion, ring infiltrate.
Corneal abrasion: fluorescein uptake, evert the lid (vertical scratches = foreign body under the upper lid), topical antibiotic, no patching, no home topical anesthetics.
Anterior uveitis: pain, consensual photophobia, ciliary flush, miosis, cells and flare (± hypopyon); HLA-B27, IBD, sarcoidosis, Behçet; topical steroid plus cycloplegic.
Acute angle closure: halos, vomiting, fixed mid-dilated pupil, steamy cornea, rock-hard eye (IOP 40–80 mmHg); lower IOP with timolol, apraclonidine, acetazolamide, then pilocarpine, then laser peripheral iridotomy; never dilate.
Scleritis = severe boring pain, violaceous, does not blanch with phenylephrine (RA, GPA; systemic therapy); episcleritis = mild pain, blanches, benign; subconjunctival hemorrhage = painless, reassure.

Triage: benign or sight-threatening?

Three questions sort most red eyes: does it hurt, is vision affected, and does light bother the patient? Check visual acuity first in every red eye, then the pupils, the cornea with fluorescein, and the pressure when angle closure is possible.

Red flags demanding same-day ophthalmology: vision loss, severe pain, photophobia, ciliary (perilimbal) flush, a fixed or mid-dilated pupil, a hazy cornea, or a contact-lens wearer. A painless red eye with normal vision and no discharge (subconjunctival hemorrhage, episcleritis) is usually benign.

Red eye at a glance

Cause	Pain and photophobia	Vision	Distinguishing sign
Conjunctivitis	Irritation or itch only	Normal	Discharge; diffuse injection
Subconjunctival hemorrhage	None	Normal	Flat, sharply bordered red patch
Episcleritis	Mild or none	Normal	Sectoral redness that blanches
Keratitis	Pain, photophobia	Often reduced	Corneal ulcer or infiltrate on fluorescein
Anterior uveitis	Pain, direct and consensual photophobia	Mildly reduced	Ciliary flush, miosis, cells and flare
Angle-closure glaucoma	Severe, with headache and vomiting	Reduced, halos	Fixed mid-dilated pupil, steamy cornea, rock-hard globe
Scleritis	Severe, boring, wakes from sleep	May be reduced	Violaceous, non-blanching vessels

Conjunctivitis

Discharge sorts the cause. Vision is normal and pain is minimal; the character of the discharge and the associated findings name the type.

Conjunctivitis by type

Type	Discharge and clues	Treatment
Viral (adenovirus, "pink eye")	Watery; foreign-body sensation; tender preauricular node; follicular reaction; often after a URI; one eye then both	Supportive: cool compresses, hygiene, hand-washing; contagious for 10–14 days; antibiotics do not help
Bacterial	Thick purulent discharge; lids matted or stuck shut on waking	Topical erythromycin or trimethoprim-polymyxin; topical fluoroquinolone for contact-lens wearers (Pseudomonas)
Gonococcal	Hyperacute, copious, rapidly re-accumulating pus	IM or IV ceftriaxone; emergency, because it can perforate the cornea
Allergic	Bilateral itching (the key symptom); watery or ropey discharge; chemosis; cobblestone tarsal papillae; atopy or seasonal triggers	Topical antihistamine/mast-cell stabilizer (olopatadine); allergen avoidance

A bilateral watery red eye with a palpable preauricular node after a cold is adenovirus: reassure, stress hand hygiene, and avoid antibiotics.

Keratitis and corneal injury

Herpes simplex keratitis. Pain, photophobia, and a branching dendritic ulcer that stains with fluorescein; a dendrite is HSV until proven otherwise. Treat with topical antivirals (trifluridine, ganciclovir gel) or oral acyclovir.

Topical corticosteroids alone are contraindicated in HSV keratitis: they enlarge the ulcer (into a geographic ulcer) and risk corneal perforation.

Contact-lens keratitis. Pain, photophobia, and a corneal infiltrate or ulcer in a lens wearer. Pseudomonas aeruginosa is the classic rapid, sight-threatening cause and can melt the cornea rapidly. Acanthamoeba, linked to water exposure (swimming or rinsing lenses in tap water), causes pain out of proportion to the exam and a ring infiltrate. Stop lens wear, refer urgently, and use fortified or fluoroquinolone drops.

Corneal abrasion. Pain, tearing, foreign-body sensation, and photophobia, with a fluorescein-staining defect. Evert the upper lid to find a retained foreign body; vertical linear ("ice-rink") abrasions imply one trapped under the upper lid.

Treat with a topical antibiotic, with Pseudomonas coverage for lens wearers.
Do not patch, especially in contact-lens wearers.
Never prescribe topical anesthetics for home use; they delay healing.

A chemical splash, especially alkali, needs immediate copious irrigation until the pH normalizes, before any other examination or history.

Anterior uveitis and acute angle-closure glaucoma

Anterior uveitis (iritis). Eye pain, photophobia, ciliary flush (perilimbal injection), a small (miotic) pupil, and cells and flare in the anterior chamber, sometimes with a hypopyon. It is linked to HLA-B27 spondyloarthropathies, IBD, sarcoidosis, and Behçet disease. Refer; ophthalmology treats with topical steroids plus a cycloplegic, which relieves ciliary spasm and prevents adhesions.

Consensual photophobia (pain in the affected eye when light shines in the other eye) points to iritis rather than conjunctivitis.

Acute angle-closure glaucoma. Severe eye pain, headache, nausea and vomiting, halos around lights, a fixed mid-dilated pupil, a steamy (hazy) cornea, and a rock-hard globe; IOP is often 40–80 mmHg. Attacks are precipitated by dim light or mydriatics, and risk is higher in older, hyperopic patients with shallow anterior chambers.

RecognizePain, halos, mid-dilated pupil, hard eye; do NOT dilate.
Lower IOP nowTimolol, apraclonidine, and acetazolamide; IV mannitol if needed.
Add pilocarpineMiosis pulls the iris out of the angle once the pressure falls.
DefinitiveLaser peripheral iridotomy; the fellow eye is usually treated prophylactically.

Acute angle-closure management

Scleritis, episcleritis, and subconjunctival hemorrhage

Scleritis versus episcleritis

Feature	Scleritis	Episcleritis
Pain	Severe, boring, wakes from sleep	Mild or none
Appearance	Violaceous hue, deep vessels	Sectoral bright redness
Topical phenylephrine	Does NOT blanch	Blanches
Associations	RA, granulomatosis with polyangiitis	Usually idiopathic
Course and treatment	Vision-threatening; systemic NSAIDs or steroids	Benign, self-limited

Subconjunctival hemorrhage. A flat, painless, sharply bordered red patch with normal vision and no discharge, caused by Valsalva, cough, trauma, anticoagulation, or hypertension. It is benign and clears over 1–2 weeks; reassure. Check blood pressure and coagulation studies if it recurs.