Red Eye Emergency Management: Causes, Red Flags and Care

Ophthalmology • Acute red eye • Emergency-medicine teaching note

Purpose. This stand-alone lecture expands the supplied 66-slide presentation, Causes and Management of Red Eyes, into a detailed clinical approach for emergency-medicine students. It follows the presentation’s objectives, epidemiology, anatomy and pathophysiology; its full lid, conjunctival, corneal, scleral, uveal, orbital, lacrimal, traumatic and infectious differential; its clinical history and examination; and its red flags and referral principles. Some source slides contain older treatment suggestions. Where these could cause harm or no longer reflect safe practice, the safer current approach is explained.

Start with sight and globe integrity. A red eye with reduced vision, moderate or severe pain, photophobia, corneal opacity, an abnormal pupil, contact lens use with pain, recent eye surgery, penetrating injury, chemical exposure or orbital signs is not routine conjunctivitis. Check vision in each eye, look at the cornea and pupil, identify open-globe risk, and arrange emergency or same-day ophthalmology according to the finding. Irrigate a chemical eye injury immediately; do not delay irrigation to finish history or examination.

Learning objectives

Explain why ocular redness occurs and distinguish superficial conjunctival redness from ciliary flush, deep scleral inflammation and blood in the subconjunctival space.
Take a focused history and conduct a safe, structured eye examination for a patient with redness.
Separate commonly self-limited causes from emergencies without assuming that a red eye is benign.
Recognize the supplied slides’ eyelid, conjunctival, corneal, scleral, uveal, orbital, lacrimal, traumatic and infectious causes.
Provide safe first aid, infection-control advice, follow-up and a clear ophthalmology handover.

1. What “red eye” means

Red eye is a sign, not a diagnosis. It usually reflects dilation or engorgement of vessels on the conjunctiva, episclera, sclera or ciliary body. A superficial diffuse redness often accompanies conjunctivitis or irritation. A circumcorneal (ciliary) flush can point to corneal disease, anterior uveitis or acute angle closure. A sharply demarcated bright-red patch may be a subconjunctival haemorrhage. Deep, violaceous redness with marked pain suggests scleritis. These appearances overlap, and a normal-looking white sclera does not rule out serious intraocular disease.

The 66-slide deck describes red eye as a frequent presentation, with both self-limited disorders and sight- or life-threatening causes. Its epidemiology slides quote local clinic figures from Nigeria and Ghana, including high proportions of allergy and microbial conjunctivitis. Those are historical facility-based observations, not current population estimates and not a universal ranking. Case mix varies with setting, season, access to care and referral patterns. For emergency practice the more important point is that serious diagnoses may be uncommon but carry high cost when missed.

1.1 Relevant anatomy and why the redness pattern helps

The visible ocular surface includes the bulbar conjunctiva covering the front of the sclera, the palpebral conjunctiva lining the lids, the clear cornea, and superficial episcleral vessels over the sclera. The anterior chamber lies behind the cornea and in front of the iris and lens; inflammation there may produce cells, flare, a small or irregular pupil and ciliary flush. The orbit encloses the globe, extraocular muscles, optic nerve, vessels and fat behind the orbital septum. Infection posterior to the septum (orbital cellulitis) threatens vision and can spread intracranially.

Redness follows vascular dilation, inflammation, infection, trauma, raised intraocular pressure, a disrupted vessel wall or bleeding beneath the conjunctiva. Pain, photophobia, vision loss, corneal change and pupil abnormalities help localize the process, but symptoms alone are not reliable enough to make the diagnosis. A corneal abrasion can be extremely painful with little visible redness; endophthalmitis can present as a red eye with profoundly reduced vision; and a quiet-looking eye can conceal posterior disease.

2. Emergency triage: who needs urgent eye care?

Finding or context	Important possibilities	Disposition
Reduced or suddenly changed visual acuity, relative afferent pupillary defect, or absent/dull red reflex	Keratitis/ulcer, uveitis, acute angle closure, endophthalmitis, retinal or optic nerve disease	Emergency or same-day ophthalmology; do not discharge as simple conjunctivitis.
Moderate/severe pain, photophobia, ciliary flush, corneal opacity or epithelial defect	Corneal abrasion/foreign body, microbial or herpetic keratitis, uveitis, scleritis, angle closure	Urgent assessment, fluorescein examination when safe, and referral based on findings.
Contact lens use with pain, redness, photophobia or blur	Microbial keratitis, including potentially rapidly progressive Pseudomonas or Acanthamoeba infection	Same-day urgent eye assessment. Remove lens if easy; do not reinsert it.
Recent intraocular surgery, intravitreal injection or penetrating trauma with pain/blur/redness	Endophthalmitis or open globe	Immediate ophthalmology/hospital transfer; shield a possible open globe.
Proptosis, painful or restricted extraocular movement, diplopia, reduced vision, RAPD, fever or severe headache	Orbital cellulitis, orbital abscess, orbital compartment syndrome, intracranial spread	Emergency admission, urgent ophthalmology/ENT and imaging when indicated.
Sudden severe eye pain with headache, halos, nausea or vomiting, cloudy cornea and mid-dilated poorly reactive pupil	Acute angle-closure glaucoma	Immediate IOP-lowering care under local emergency protocol and urgent ophthalmology.
Chemical splash, lime/cement in the eye, or unknown caustic exposure	Chemical ocular burn	Start copious irrigation immediately; continue while arranging emergency assessment.
Suspected penetrating injury, high-velocity fragment or irregular/peaked pupil after trauma	Open-globe injury	Rigid shield without pressure; urgent transfer. Avoid tonometry, patching, manipulation and removal of an embedded object.
Hyperacute copious purulent discharge, marked lid oedema or corneal involvement	Gonococcal infection, severe bacterial conjunctivitis, keratitis	Urgent sampling, systemic treatment and ophthalmology/sexual-health input as appropriate; topical therapy alone is inadequate for gonococcus.
Neonate with a red or discharging eye, especially with lid swelling, maternal STI risk, vesicles or fever	Gonococcal/chlamydial ophthalmia, HSV, other infection or sepsis	Urgent hospital/paediatric assessment; obtain age-appropriate samples and systemic management.

Classic red flags: sudden visual loss; severe or deep pain; pain with photophobia; corneal opacity or fluorescein staining; abnormal or fixed pupil; hypopyon; proptosis or restricted movements; trauma or chemical exposure; contact lens risk; very high intraocular pressure if measured; and the combination of pain, photophobia and reduced visual acuity. No single numeric IOP threshold should be used as the only referral trigger: measurement technique, corneal injury and clinical appearance matter, and a number must never delay referral.

3. Focused history

Ask the following in a direct, organized way. In a busy emergency department, a few discriminating questions can reveal a vision-threatening cause.

Onset and course: sudden or gradual; hours, days or weeks; worsening or improving; first episode or recurrence. Was redness present on waking or after a specific event?
Distribution and laterality: one eye, both eyes, sequential involvement, or a localized sector? Unilateral “conjunctivitis” with pain, corneal change or recurrent episodes deserves diagnostic caution.
Pain and sensation: itch, gritty/burning irritation, foreign-body sensation, sharp pain with blinking, deep boring ache, pain at night, pain on eye movement, or headache? Itching strongly supports allergy; deep severe pain suggests scleritis or intraocular disease.
Visual symptoms: blur, reduced acuity, halos, diplopia, floaters, flashes, curtain/field loss, photophobia or difficulty opening the eye. Ask whether vision clears after wiping discharge; persistent blur is concerning.
Discharge and watering: watery, stringy/mucoid, mucopurulent, copious purulent, or blood-stained? Discharge can suggest an etiology but does not by itself rule in or out serious disease.
Trauma/exposure: fingernail, vegetation, dust, metal grinding, drilling, high-velocity fragments, foreign body, UV exposure, chemical splash, smoke, contact with lime or cement, or water exposure while wearing contact lenses. Identify the agent and time, but irrigate chemical exposure before completing the history.
Contact lenses: type, overnight wear, swimming/showering in lenses, cleaning solution, last removal and whether the patient slept in them. Ask the patient to bring the lens and case when microbial keratitis is suspected.
Recent procedures and drops: eye surgery, injection, laser, prior ulcer or herpes; contact with topical steroids, anaesthetic, vasoconstrictor “redness relief” drops, traditional remedies, shared cosmetics or contaminated solutions.
Exposure/infection: sick contacts, respiratory symptoms, travel, immunosuppression, atopy, facial or eyelid vesicles, forehead/nasal rash, or STI symptoms/exposure. Ask sensitively and confidentially when indicated.
Medical context: autoimmune disease (for example rheumatoid arthritis, vasculitis or inflammatory bowel disease), diabetes, HIV/immunosuppression, bleeding disorder, hypertension, anticoagulant/antiplatelet use, pregnancy, recent vomiting/coughing, and relevant medication allergies.
In children: birth and maternal STI history for a neonate, immunization and systemic symptoms, safeguarding concerns after trauma, ability to fix/follow, and whether one eye is consistently shut or rubbed.

4. Safe, structured examination

Assess the whole patient and immediate stability. Look for fever, toxicity, rash, facial swelling, proptosis, trauma, neurologic symptoms, sepsis or airway concern. Treat systemic emergencies alongside the eye.
Measure visual acuity in each eye separately before drops or procedures. Use the patient’s usual correction, then pinhole if reduced and feasible. For a preverbal child document fixation/following and compare each eye using gentle occlusion. Record “unable to assess” and why; do not substitute “vision normal” for an untested eye.
Inspect from the front: symmetry, eyelid oedema, erythema, vesicles, crusting, lash misdirection, lid margin disease, ptosis, incomplete closure, proptosis, conjunctival swelling (chemosis), diffuse versus sectoral redness, and the location of any bleeding.
Examine conjunctiva and fornices. Note follicles, papillae, membranes, discharge and focal lesions. Evert the upper lid if a superficial foreign body is suspected and there is no concern for open globe. A retained subtarsal particle can cause repeated vertical corneal scratches.
Inspect cornea and anterior chamber. Look for clarity, infiltrate/white spot, ulcer, foreign body, dendritic lesion, abrasion, oedema, blood or hypopyon. Fluorescein under cobalt-blue illumination identifies epithelial defects and may show a dendrite; assess Seidel leakage only when appropriate and never press on an obvious open globe. If the cornea is hazy, a pupil is abnormal or view is obscured, treat as urgent.
Check pupils and eye movements. Record size, shape, reactivity, anisocoria and any relative afferent pupillary defect. Test extraocular movements, pain, restriction and diplopia. A peaked/irregular pupil after injury can mark open-globe trauma; do not manipulate it.
Palpation and pressure: assess globe tenderness only gently. Tonometry is appropriate only when open globe is not suspected and the clinician is trained. Do not “compare hardness” by pressing on injured eyes. Avoid dilation if acute angle closure is possible until specialist advice.
Additional tests as indicated: preauricular nodes, skin/forehead V1 rash, fundus examination if safe and possible, blood pressure in a subconjunctival haemorrhage, swabs/cultures for severe or atypical infection, STI testing when indicated, and orbital CT/MRI for suspected orbital disease. Testing should not delay irrigation, shield and referral.

Topical anaesthetic note: a clinician may use a single supervised dose to facilitate an examination or irrigation according to local practice. Do not send the patient home with repeated topical anaesthetic use unless a specialist-approved protocol specifically directs it; repeated use can injure corneal epithelium, mask deterioration and delay care.

5. Less often sight-threatening causes: recognize and manage safely

“Non-sight-threatening” is a useful teaching category, not a guarantee. The following disorders are often managed conservatively only when visual acuity is preserved, the cornea is clear, pain is mild, the pupil is normal, and no red flag is present. Worsening symptoms or diagnostic uncertainty changes the plan.

5.1 Blepharitis and marginal keratitis

Blepharitis is chronic inflammation at the lid margin, often associated with staphylococcal colonization, seborrhoeic dermatitis or meibomian-gland dysfunction. Patients report burning, itch, gritty sensation, crusting, tearing and intermittent blur that clears with blinking. Look for collarettes/scales at lash bases, lid-margin erythema, plugged glands and sometimes lash loss or chronic conjunctival irritation. Treat with regular warm compresses, gentle lid cleaning, hand hygiene and lubricating drops; manage rosacea/seborrhoea when present. Swab only when recurrent, severe or treatment-resistant infection is suspected. Antibiotic or steroid ointment is not routine and prolonged topical steroid exposure can raise IOP, cause cataract and worsen infection.

Marginal keratitis is peripheral corneal inflammation, sometimes related to staphylococcal lid disease; distinguish it from microbial corneal ulcer. A peripheral infiltrate with an epithelial defect, contact lens use, significant pain, photophobia, central extension or reduced vision needs urgent ophthalmology. Do not start steroid drops on an undiagnosed red eye.

5.2 Trichiasis, chalazion and hordeolum (stye)

Trichiasis means misdirected lashes rubbing the globe. It causes foreign-body sensation, tearing, photophobia and recurrent abrasions. Remove an offending lash only if trained and there is no trauma concern; recurrent or multiple lashes need ophthalmology and evaluation for scarring disorders such as trachoma or cicatricial lid disease. Check for corneal staining.

A hordeolum (stye) is an acute tender focal infection/inflammation of an eyelid gland: external at a lash-associated gland or internal in a meibomian gland. A localized tender red nodule is typical. Warm compresses and avoidance of squeezing are reasonable. Topical antibiotics are not routinely beneficial for an uncomplicated internal lesion; systemic antibiotics are for spreading preseptal cellulitis or systemic illness and follow local protocols. Painful diffuse swelling, fever, proptosis or painful/restricted eye movement suggests more than a simple stye.

A chalazion is a chronic, usually painless meibomian-gland obstruction and granulomatous nodule. Warm compresses and gentle massage are first-line; many resolve over weeks. Large lesions can induce astigmatism or amblyopia in a child. Persistent, recurrent, atypical or lash-loss lesions need ophthalmology to confirm the diagnosis and consider incision/curettage or other treatment. Oral tetracyclines are not a routine “lipid-transforming” treatment; avoid them in young children and pregnancy, and reserve systemic anti-inflammatory treatment for selected specialist-managed disease.

5.3 Conjunctivitis: bacterial, viral, allergic and chemical/toxic

Simple conjunctivitis causes diffuse conjunctival redness with discharge or itch; vision is usually normal after wiping discharge, the cornea is clear, and severe pain or photophobia is absent. Unilateral redness needs caution, particularly if there is pain, trauma, reduced vision or corneal opacity.

Viral conjunctivitis (often adenovirus) commonly causes watery discharge, burning/gritty discomfort, follicles, preauricular nodes and sometimes an upper respiratory infection. The second eye may become involved over several days; symptoms can last one to three weeks and occasionally longer. Use cool compresses, lubricants, handwashing, separate towels, clean pillowcases and avoid sharing eye drops or cosmetics. It is highly contagious. Antibiotics do not treat adenovirus. Routine topical steroids are unsafe outside ophthalmology because they may prolong infection, worsen herpetic disease or raise pressure. Severe pain, photophobia, reduced vision, corneal involvement, pseudomembrane or immunocompromise warrants eye review.

Allergic conjunctivitis is usually bilateral and itch is the prominent symptom. There may be watery or stringy mucus, chemosis, lid swelling, atopy or seasonal triggers. Advise allergen avoidance where practical, cold compresses and lubricants; an age-appropriate topical antihistamine/mast-cell stabilizer can be used according to local guidance. Avoid prolonged vasoconstrictor “get the red out” combinations because of rebound redness and adverse effects. Severe atopic keratoconjunctivitis, corneal involvement or significant photophobia needs specialist care. Steroids or topical NSAIDs are not casual first-line therapy.

Uncomplicated acute bacterial conjunctivitis often has mucopurulent discharge and lids stuck on waking; it is not invariably bacterial, and mild cases may resolve without antibiotics. Gentle lid cleaning and hand hygiene are reasonable. If local guidance recommends a topical antibiotic for a selected case, use the locally approved drug and duration. Do not prescribe the same antibiotic automatically to every red eye. Contact lens wear, corneal opacity, severe pain, hyperacute discharge, neonate, immunocompromise, treatment failure or recurrent disease calls for sampling and urgent/specialist assessment.

Hyperacute gonococcal conjunctivitis may progress rapidly with copious purulent discharge, marked chemosis and lid oedema and can perforate the cornea. Obtain urgent samples where feasible, but do not delay systemic treatment and ophthalmology/infectious-disease input. Topical drops alone are inadequate. CDC guidance for adolescents and adults lists ceftriaxone 1 g intramuscularly once and consideration of saline lavage; neonatal disease requires urgent paediatric protocols, appropriate cultures/testing and systemic management. Check for and manage coexisting STI and partners using current local guidelines and confidential care.

Chlamydial conjunctivitis in adults is often unilateral, subacute or persistent follicular conjunctivitis with mucopurulent discharge and a preauricular node; a genital infection may be asymptomatic. It requires systemic, age- and pregnancy-appropriate treatment, STI assessment and partner evaluation. Topical therapy alone is inadequate. In a neonate, consider chlamydia in conjunctivitis within the first month, often presenting around days 5–12; it may coexist with later afebrile pneumonia. The infant needs systemic treatment and follow-up under paediatric guidance; do not apply adult doxycycline regimens or drops as a universal regimen.

Chemical/toxic conjunctivitis can follow a splash, fumes, inappropriate eye drops, cosmetics or traditional remedies. Treat a caustic splash as an emergency burn and irrigate first. Stop the suspected non-essential offending product, document exposure and assess cornea and vision; persistent symptoms or epithelial damage require urgent ophthalmology. Avoid trying to chemically neutralize the agent.

5.4 Subconjunctival haemorrhage

This is blood between conjunctiva and sclera, appearing as a sharply demarcated bright-red patch. Typical spontaneous haemorrhage is painless with normal acuity, pupil and eye movement. It may follow coughing, vomiting, straining, minor trauma or occur without a recognized trigger; anticoagulants and hypertension may contribute. Reassure that uncomplicated blood usually clears gradually over one to three weeks, and lubricants may help irritation. Check blood pressure and medication/bleeding history when clinically appropriate. NSAIDs are not categorically contraindicated for every patient, but review bleeding risk and do not add aspirin for eye redness.

Trauma changes the assessment: bilateral haemorrhage, a 360-degree subconjunctival haemorrhage, inability to see its posterior extent, pain, reduced vision, hyphema, abnormal pupil or high-energy mechanism can indicate serious ocular/orbital injury. In children assess safeguarding sensitively and appropriately. Recurrent, persistent or unexplained episodes may need review for hypertension, anticoagulation or bleeding disorder. Refer for associated pain, visual change, trauma or uncertainty.

5.5 Dry eye

Dry-eye disease reflects insufficient tear production, excess evaporation or tear-film instability. Burning, fluctuating blur, gritty sensation and reflex tearing often worsen through the day, in wind, low humidity, air conditioning or sustained screen use. Contributors include meibomian dysfunction, incomplete blink/facial nerve weakness, medications with anticholinergic effects, antihistamines, contact lens wear, vitamin A deficiency, autoimmune disease such as Sjögren syndrome, and prior surgery. Review medicines without stopping essential treatment abruptly. Mild symptoms may improve with environmental changes and preservative-free lubricants. Schirmer testing, punctal plugs and tarsorrhaphy are selected tools for particular chronic disease, not automatic emergency treatments. Marked unilateral pain, photophobia, corneal staining, reduced vision or contact-lens-associated pain is not assumed to be dry eye.

5.6 Pinguecula and pterygium

A pinguecula is a yellowish conjunctival elevation, commonly near the nasal limbus, associated with chronic sun, wind and dust exposure. It usually does not grow across the cornea. Local inflammation (pingueculitis) can cause sectoral redness or gritty discomfort. A pterygium is a fibrovascular triangular growth of conjunctiva that extends onto the cornea; it can induce astigmatism, distort vision or approach the visual axis. Both can be managed with lubricants, sunglasses/UV protection and reduction of wind/dust exposure. Refer for visual-axis threat, progressive growth, induced refractive change, persistent inflammation or atypical mass. Steroid or NSAID drops and surgery require clinical selection and monitoring; vasoconstrictors can mask redness without treating its cause.

5.7 Corneal abrasion and superficial foreign body

Abrasion follows fingernail, paper, dust, foreign body, contact lens, dry surface or ultraviolet exposure. It causes tearing, sharp pain, blepharospasm, photophobia and foreign-body sensation, often worse with blinking. Evert the upper lid when safe to find a subtarsal particle. Fluorescein outlines an epithelial defect. Exclude penetrating injury before manipulating the eye. A superficial abrasion in a patient with normal vision and no infiltrate may be treated with locally recommended prophylaxis/analgesia and planned review. Contact-lens-associated epithelial defects have a higher microbial keratitis risk and require urgent clinician review and coverage according to local protocol.

Do not patch routinely; patching can delay recognition and may increase infection risk in contact-lens wearers. Do not prescribe take-home topical anaesthetic or start steroid drops. Cycloplegics and bandage contact lenses are not automatic; use only when indicated and appropriately supervised. Reassess if pain fails to improve, vision falls or an infiltrate appears.

6. Vision-threatening causes and emergency response

6.1 Preseptal versus orbital cellulitis

Preseptal (periorbital) cellulitis is infection anterior to the orbital septum; the globe and orbital contents are not involved. Patients have lid erythema, warmth, swelling and tenderness, but normally preserved vision, no proptosis, full painless extraocular movements and no RAPD. Orbital cellulitis is postseptal infection, commonly related to sinus disease, and is a surgical/medical emergency with risks of optic neuropathy, abscess, cavernous sinus thrombosis and intracranial infection.

Red flags are pain with eye movement, restricted motility, diplopia, proptosis, reduced acuity, RAPD, severe headache, fever/toxicity or neurological signs. Admit, keep fasting if surgery may be needed, obtain urgent ophthalmology and ENT advice, begin IV antimicrobials according to local resistance patterns, and arrange contrast imaging when it will change care. A lumbar puncture is contraindicated when orbital/intracranial extension and raised pressure are concerns. Abscess drainage is considered by the specialist team; surgery is not required in every case. Do not send a child with suspected orbital cellulitis home on oral antibiotics alone.

6.2 Scleritis versus episcleritis

Episcleritis is superficial inflammation, often sectoral, with mild irritation/tenderness, watering and largely preserved vision. It may recur and can accompany systemic inflammatory disease. Many cases settle; lubricants and follow-up are reasonable after serious causes have been excluded. Deep, severe, boring pain (often worse at night or with eye movement), marked tenderness, violaceous hue, reduced vision or associated corneal/uveal disease suggests scleritis. Scleritis can be necrotizing or posterior and can threaten the globe. It is associated with rheumatoid arthritis, vasculitis and other autoimmune disease, and sometimes infection including zoster. Arrange urgent ophthalmology and systemic assessment. Do not treat suspected infectious scleritis with immunosuppression or topical steroids without specialist direction.

6.3 Anterior uveitis (iritis)

Anterior uveitis is inflammation of the iris and ciliary body. Typical findings are ciliary flush, aching pain, consensual photophobia, reduced vision, a small or irregular sluggish pupil, anterior-chamber cells/flare and sometimes hypopyon. The cause may be idiopathic, autoimmune/inflammatory, infectious, traumatic or drug-related. HLA-B27 is an association, not a diagnosis; ask about inflammatory back pain, arthritis, bowel disease, psoriasis, oral/genital ulcers and systemic symptoms. Intermediate and posterior uveitis may not produce the classic red eye but can cause floaters or reduced vision.

Arrange same-day or urgent ophthalmology. Cycloplegic drops and topical corticosteroids may be required but should be initiated and monitored by an eye clinician after infectious keratitis (especially HSV) is considered. Unsupervised steroid drops can worsen active epithelial herpes, fungal infection or bacterial ulcer and can raise IOP. Follow-up matters because recurrent inflammation can cause synechiae, glaucoma, cataract and macular oedema.

6.4 Acute angle-closure glaucoma

Acute primary angle closure causes rapid obstruction of aqueous outflow and a potentially damaging rise in intraocular pressure. Symptoms can include sudden severe ocular/periocular pain, blurred vision or colored halos, headache, nausea/vomiting and a red watery eye. Signs include corneal oedema/haze, a shallow anterior chamber, a mid-dilated poorly reactive pupil and markedly raised IOP if it is safely measured. The patient may initially be misdiagnosed with migraine, abdominal illness or conjunctivitis.

This is an ophthalmic emergency. Contact ophthalmology immediately; provide analgesia/antiemetic support and start pressure-lowering treatment under the current local protocol with appropriate contraindication checks and monitoring. Definitive care usually includes laser peripheral iridotomy once feasible, often with assessment/treatment of the fellow eye. Do not use a fixed copied drug bundle without examining the patient and checking asthma, bradycardia/heart block, pregnancy, renal status and the suspected mechanism. Pilocarpine may be ineffective or harmful at very high pressure or in secondary/non-pupillary-block mechanisms; it is not a reflex first drop before specialist guidance. Do not lie the patient flat as a treatment and do not delay escalation while seeking an exact IOP threshold.

6.5 Microbial and herpetic keratitis

Microbial keratitis/corneal ulcer causes pain, photophobia, tearing, redness, reduced vision and a focal white/grey corneal infiltrate, sometimes with an epithelial defect, discharge, anterior-chamber reaction or hypopyon. Contact-lens wear (especially overnight, poor hygiene or swimming in lenses), trauma, topical steroids, dry/exposed cornea and immunosuppression increase risk. It may progress rapidly and scar or perforate the cornea. Same-day ophthalmology is required. Culture/scrape decisions and intensive topical antimicrobial selection are specialist-directed; in severe disease obtain samples when feasible without delaying treatment. Stop contact lenses and retain the lens/case for possible culture. Do not patch, prescribe a take-home anaesthetic or start steroids before infection is characterized.

Herpes simplex keratitis may recur as a unilateral red, painful, watery, photophobic eye with corneal hypoesthesia and a branching dendritic epithelial lesion on fluorescein. HSV lid vesicles or a prior unilateral “conjunctivitis” support the possibility but may be absent. Herpes zoster ophthalmicus causes a painful vesicular rash in the ophthalmic (V1) distribution of the trigeminal nerve; lesions on the forehead or nose increase concern for ocular involvement, but their absence does not exclude it. Eye pain, red eye, photophobia, reduced vision, corneal findings or immunocompromise warrants urgent eye review and prompt systemic antiviral treatment under local guidance. Avoid topical steroids in suspected epithelial HSV unless an ophthalmologist directs them for a specific stromal/uveitic indication with antiviral cover.

6.6 Endophthalmitis

Endophthalmitis is infection/inflammation inside the globe, commonly after surgery, intravitreal injection or penetrating trauma, and occasionally from bloodstream infection. Severe pain, rapid reduction in vision, hypopyon, marked redness and sometimes lid swelling are typical, though symptoms vary. This is an immediate ophthalmology emergency. Do not delay transfer for routine swabs or imaging. The eye specialist may obtain intraocular samples and administer intravitreal antimicrobial treatment; systemic management is guided by cause and protocol.

6.7 Hyphema and blunt trauma

Hyphema is blood in the anterior chamber after blunt trauma, ranging from microscopic red cells to a visible level. It may cause pain, photophobia and reduced vision, and can rebleed or block aqueous outflow, raising pressure. Assess for open globe, pupil abnormality, lens injury, retinal injury and orbital fracture. Place a rigid shield, elevate the head, limit activity, control pain/nausea safely and arrange urgent ophthalmology. Avoid pressure on the globe and avoid aspirin/NSAIDs when bleeding risk is relevant unless directed by a treating clinician. Check for sickle cell disease/trait where clinically appropriate because raised IOP can be especially dangerous. Do not discharge significant hyphema without specialist plan and follow-up.

6.8 Penetrating injury and suspected open globe

Mechanisms include sharp objects, high-velocity metal, glass, explosive injury, plant matter and severe blunt impact with rupture. Clues include a peaked/teardrop pupil pointing to a wound, uveal prolapse, irregular or shallow chamber, abnormal globe contour, blood, very poor vision, positive Seidel leakage or a visible embedded object. A normal-looking external eye does not exclude a small penetration.

Do not press, patch, tonometer-measure, irrigate forcefully, evert lids, remove an embedded object or apply topical medication when an open globe is suspected. Place a rigid eye shield without pressure, keep the patient nil by mouth in case surgery is required, control pain/vomiting, give tetanus prophylaxis and systemic antibiotics according to the local open-globe protocol, and transfer immediately to ophthalmology. Imaging such as CT orbit is directed by the specialist/trauma team; MRI is avoided if a metallic foreign body is possible.

6.9 Chemical and thermal injury

Chemical burns are time-critical. Alkali (cement, lime, drain cleaner, ammonia) can penetrate rapidly; acids can also cause severe injury. Thermal burns, hot liquids, steam and ultraviolet exposure have distinct mechanisms but still need corneal assessment. First ensure scene safety and protect staff. Remove contact lenses and loose particulate matter if feasible; for dry lime/cement particles, gently brush visible debris from surrounding skin and fornices while irrigating, without delaying lavage.

Start copious irrigation at once with clean tap water, saline or another non-toxic available fluid. Do not wait for pH strips, topical anaesthetic, history, transport or sterile fluid. Irrigate from the nasal side outward, keeping contaminated runoff away from the other eye. Evert lids and sweep retained particles when safe and trained. Check ocular surface pH after an initial irrigation, pause briefly and recheck because retained chemical can cause rebound; continue until neutral and stable according to local protocol. A Morgan lens can help deliver irrigation but does not remove solid particles. Do not attempt acid/base neutralization, which can generate heat and worsen injury. After irrigation, urgent ophthalmology is required to assess limbal damage, corneal epithelium, pressure and need for treatment. Continue irrigation during transport if necessary.

7. Other causes named in the slide deck

7.1 Subtarsal foreign body

A foreign body trapped beneath the upper lid often causes persistent foreign-body sensation and linear vertical fluorescein staining. Evert the lid only after open globe has been excluded; remove a superficial particle only when trained and safe. A metallic corneal foreign body, rust ring, deeply embedded particle, central lesion, high-velocity mechanism or uncertain depth needs ophthalmology. Never remove an embedded or protruding object from a possible open globe. Update tetanus care where indicated.

7.2 Canaliculitis and lacrimal sac disease

Canaliculitis is an uncommon infection of a canaliculus, often presenting as chronic unilateral tearing or recurrent “conjunctivitis,” a pouting punctum and expressible concretions. It is frequently missed because it resembles routine conjunctivitis. Ophthalmology is needed for confirmation and definitive treatment; repeated topical antibiotics alone may fail.

Dacryoadenitis is inflammation of the lacrimal gland, producing painful swelling in the outer upper eyelid, sometimes with S-shaped ptosis. Infectious causes can coexist with fever/systemic illness; inflammatory disease is also possible. Examine for proptosis and movement restriction and assess the patient’s general state. Orbital signs or toxicity need urgent hospital care.

Dacryocystitis is infection of the lacrimal sac, classically with painful redness and swelling below the medial canthal tendon and sometimes reflux of pus from the punctum. It can progress to abscess or orbital/intracranial infection. Fever, systemic illness, an infant, rapidly spreading redness or orbital signs requires urgent hospital/ophthalmology assessment and systemic antibiotics under local guidance. Do not confuse it with uncomplicated nasolacrimal obstruction; avoid lacrimal massage over a painful infected sac.

7.3 Factitious or functional presentations

The source deck lists factitious red eye. This term must be used carefully. A mismatch between symptoms, reported mechanism and observed signs does not prove intentional illness. First exclude organic disease and injury, consider ocular surface irritation from drops or topical substances, obtain collateral history when appropriate, and document objective findings without accusation. Use a non-judgmental approach and involve senior, mental-health or safeguarding services only when the clinical context supports it. A patient with trauma, self-harm risk or a vulnerable child requires appropriate safety assessment; no one should be denied eye care because symptoms appear inconsistent.

8. Practical initial-management pathway

Is there a chemical exposure? If yes, begin irrigation now and continue while arranging emergency assessment.
Could the globe be open? If yes or uncertain after high-risk trauma, shield without pressure; avoid examination maneuvers that press or manipulate the globe and transfer urgently.
Is vision reduced or is there severe pain, photophobia, corneal opacity, abnormal pupil or orbital sign? If yes, classify as urgent/emergency and contact ophthalmology; do not label it uncomplicated conjunctivitis.
Is the patient a contact-lens wearer with pain or photophobia? Treat as possible microbial keratitis; remove lens if easy, stop wear and arrange same-day assessment.
Does the presentation fit a simple surface disorder? Confirm normal acuity, clear cornea, normal pupil and full movements; provide symptom care, infection-control advice when contagious, explicit return precautions and a defined follow-up plan.
Is the cause uncertain? Get senior/ophthalmology advice. Uncertainty is itself a reason not to prescribe steroid drops or discharge without a safety net.

8.1 Safety-net instructions for discharge

Explain exactly when and where to return. Seek urgent reassessment for worsening pain, any new blur or vision loss, light sensitivity, inability to open the eye, a white/grey spot on the cornea, increasing lid/facial swelling, fever, double vision, restricted eye movement, new rash around the eye, persistent or increasing discharge, contact-lens-related symptoms, or no improvement within the stated review period. Stop contact-lens use until the eye is fully recovered and a clinician says it is safe. Do not share towels, pillows, cosmetics or drops when contagious conjunctivitis is suspected. Provide written information where possible and confirm the patient has transport and access to follow-up.

9. Cases for emergency-medicine students

Case 1: Itchy watery eyes in spring

A student has bilateral itch, watery/stringy discharge, sneezing and a clear cornea. Vision returns to baseline when tears are wiped and pupils are normal. Allergy is likely. Use cold compresses, lubricants and an age-appropriate antihistamine/mast-cell stabilizer if indicated; review if pain, photophobia or blur develops. Do not use a vasoconstrictor or steroid by default.

Case 2: Red eye in a contact-lens wearer

A 22-year-old slept in soft lenses and now has unilateral pain, photophobia and blur. A small white corneal infiltrate is visible. This is microbial keratitis until proven otherwise, not routine conjunctivitis. Stop lens wear, keep the lens/case if culture may be needed, contact ophthalmology urgently and follow their antimicrobial protocol. No patch, home anaesthetic or steroid drop.

Case 3: Pain, vomiting and halos

A 67-year-old with sudden unilateral eye pain, headache, nausea and halos has a cloudy cornea and mid-dilated poorly reactive pupil. Suspect acute angle closure. Arrange immediate pressure-lowering treatment and eye-specialist care. Check comorbidities and use local protocol; do not blindly administer pilocarpine before assessing mechanism/IOP response.

Case 4: Child with swollen lids and fever

A 7-year-old with sinus symptoms has fever, proptosis, diplopia and painful restricted eye movement. Orbital cellulitis is likely. Admit, start IV antimicrobials per local protocol, keep fasting until surgery is considered, and obtain urgent ophthalmology/ENT input and indicated contrast imaging. Preseptal cellulitis alone should not cause proptosis or painful restricted movements.

Case 5: Lime powder at work

A worker gets dry cement dust in one eye. Irrigation begins immediately and continues during transport. Remove contact lenses and particulate matter when safe, check and repeat pH after lavage, and keep irrigating until neutral and stable. Do not neutralize with vinegar or another chemical, and do not delay lavage to identify every product ingredient.

Case 6: “Pink eye” after surgery

A patient has severe pain and major visual decline several days after cataract surgery. Even if discharge is limited, endophthalmitis must be considered. This is an immediate ophthalmology emergency; do not treat as routine bacterial conjunctivitis or wait for outpatient review.

Case 7: A painless red patch after coughing

An otherwise well adult has a sharply demarcated subconjunctival red patch after a coughing episode. Acuity, pupil, motility and cornea are normal and there was no trauma. Reassure, check blood pressure/medications when appropriate and explain gradual absorption. New pain, vision change, trauma, bilateral haemorrhage or recurrence changes the assessment.

10. Self-test

Which three symptoms together should make you doubt simple conjunctivitis?
What should you document before applying drops or starting treatment?
Why is unilateral “conjunctivitis” approached cautiously?
What finding separates a simple stye from suspected orbital cellulitis?
How do episcleritis and scleritis differ clinically and in urgency?
What should you do first after a caustic splash to the eye?
Why are topical steroid drops unsafe for undiagnosed red eye?
Which red-eye symptoms in a contact-lens wearer suggest microbial keratitis?
What distinguishes preseptal from orbital cellulitis at bedside?
Which initial precautions apply to suspected open globe?
Why is topical antibiotic alone inadequate for gonococcal conjunctivitis?
How should a typical uncomplicated subconjunctival haemorrhage be managed?

Answers

Pain, photophobia and reduced visual acuity, especially when combined with corneal change or an abnormal pupil.
Visual acuity separately in each eye, pain/photophobia, corneal appearance, pupil findings, movement, laterality and relevant mechanism/risk factors.
It can reflect foreign body, keratitis, HSV, uveitis or angle closure rather than uncomplicated conjunctivitis.
Proptosis, reduced vision, fever, diplopia or painful/restricted extraocular movements are orbital warning signs.
Episcleritis is usually superficial, sectoral and mildly uncomfortable with preserved vision; scleritis is deep, often severe boring pain with possible visual loss and requires urgent specialist review.
Begin copious irrigation immediately with any clean, non-toxic available fluid and continue while arranging emergency care.
Steroids can worsen HSV epithelial keratitis, fungal/bacterial infection, increase intraocular pressure and obscure progression.
Pain, photophobia, reduced vision, corneal staining/opacity or infiltrate; urgent same-day assessment is needed.
Preseptal swelling is anterior to the septum with preserved vision and full painless movements; orbital disease may cause proptosis, painful restriction, diplopia, RAPD or vision loss.
Rigid shield without pressure, urgent transfer, nil by mouth if surgery may be needed, control pain/vomiting, no tonometry/manipulation/embedded-object removal.
Gonococcus can invade and rapidly damage cornea; systemic therapy and urgent specialist input are required.
Reassure if classic and uncomplicated, explain gradual clearing, check blood pressure/bleeding history when appropriate, and reassess if pain, vision change, trauma or recurrence occurs.

11. Key take-home points

Red eye describes a sign. Diagnose the underlying cause by combining vision, pain, photophobia, discharge, pupil, corneal and orbital findings.
Measure visual acuity separately in both eyes; a fall in vision should change urgency.
Clear cornea, normal pupil, preserved vision, mild irritation and itch support a surface diagnosis. Severe pain, photophobia, corneal opacity, contact-lens pain, trauma or abnormal pupil do not.
Irrigate chemical injuries immediately. Shield suspected open globes without pressure. Treat orbital cellulitis, microbial keratitis, endophthalmitis, hyphema and acute angle closure as urgent/emergency problems.
Do not prescribe steroid drops for an undifferentiated red eye, use take-home topical anaesthetic, or patch a potentially infected corneal lesion by routine.
Antibiotics are not required for every conjunctivitis. Hyperacute purulence and neonatal conjunctivitis require systemic evaluation and treatment.
A referral must state urgency, acuity, corneal appearance, pupils, movement, trauma/contact lens/surgery history, systemic features and actions already taken.