Red eye, corneal injury and uveitis

• A red eye is a symptom, not a diagnosis: the job is to place the patient into one of a handful of sight-threatening emergencies, surface disease, or harmless self-limited conditions.
• Pain, photophobia, and any change in vision make the cornea, anterior chamber, and sclera the first places to look; itching and discharge point towards the conjunctiva.
• Corneal abrasions are common and self-healing, but contact lens wear raises the risk of microbial keratitis; chemical injuries and penetrating trauma are the true emergencies and need irrigation or shielding first.
• Anterior uveitis (iritis) is the commonest intraocular inflammatory presentation; it presents with a painful red eye, photophobia, and a small or irregular pupil.
• Scleritis is deep, boring pain that wakes the patient at night; infection can mimic it, so corticosteroids should not be started before infection is excluded.

By the end of this page you should be able to:

1. Build a differential diagnosis for a red eye grouped by threat to sight and by anatomical site.
2. Recognise the red flags that turn a red eye into an same-day ophthalmology referral.
3. Take a focused history and perform a focused examination that separates conjunctival, corneal, anterior chamber, scleral, and adnexal disease.
4. Choose investigations in order, from bedside penlight and fluorescein through slit lamp to imaging when trauma or deeper injury is suspected.
5. Manage corneal abrasion, foreign body, chemical burn, uveitis, scleritis, and conjunctivitis through the first 24 hours, including what not to do.
6. Describe how management differs for children, contact lens wearers, immunocompromised patients, and patients in low-resource settings.

A red eye is one of the most common reasons for emergency department and primary care visits. Conjunctivitis alone accounts for roughly 3% of all general medical visits, and about 1% to 3% of primary care clinic visits are for acute conjunctivitis. ^[2] More than 80% of all acute cases are diagnosed first by non-ophthalmologists such as internists, primary care clinicians, paediatricians, and nurse practitioners. ^[1] That is why every clinician needs a safe, rapid way to separate the conditions that must be referred today from those that can be managed in the community.

The key idea is anatomical. The eye is a layered sphere: the cornea over the anterior chamber, the iris and ciliary body, the sclera, and the conjunctiva in front of and around it. Each layer has its own typical pain, its own redness pattern, its own discharge, and its own danger. Reading those clues in order is what differentiates red eye causes.

A rough outline is enough to start: pain plus photophobia plus reduced vision points inward (cornea, anterior chamber, sclera, or posterior segment). Itching and mucoid discharge point outward (conjunctiva and lid margin). A red eye with no pain and no vision change is usually benign conjunctivitis; a red eye with pain and vision change demands the slit lamp today.

This is a presentation topic: it teaches the approach first, then treats each cause in enough depth to be safe.

Table: Red eye causes by site, mechanism and urgency. Every row includes the clue that separates it from its neighbour.

Clusters of causes matter as much as the list. In a first-year medical student framing there are four groups: surface disease (cornea, conjunctiva, sclera), anterior segment inflammation (iris, ciliary body), pressure emergencies, and deeper or systemic disease. Starting with that grouping, then asking about pain, vision, discharge, trauma, and contact lenses, handles most cases.

These are the signs that mean same-day ophthalmology review, regardless of how the rest of the presentation reads. They are grouped by what forces the referral.

• Vision reduced. Any new blur, mist, or loss of acuity, including a patient who simply says "I cannot see as well as before", is a red flag until examined.
• Pain that is deep, severe, or wakes the patient at night. Surface irritation is gritty and mild; scleritis is a boring ache; acute glaucoma is excruciating; chemical burns sting continuously. Severity of pain separates layers.
• Photophobia with a red eye. This points at cornea or anterior chamber inflammation and is not explained by simple conjunctivitis.
• A fixed, mid-dilated, or irregular pupil. Think anterior uveitis, acute glaucoma, or trauma.
• Hypopyon, hyphaema, or corneal ulcer. Visible inflammatory cells or blood in the anterior chamber, or a white infiltrate on the cornea.
• Chemical or thermal injury. Alkali burns in particular keep penetrating after the exposure ends. ^[5]
• Penetrating or high-velocity injury. A foreign body that may have entered the globe, glass, or hammer-and-chisel work.
• Contact lens wear with a red, painful eye. The lens itself is the risk factor for microbial keratitis, the most sight-threatening contact lens complication. ^[8]
• Neonates. Conjunctivitis in the first 4 weeks of life includes ophthalmia neonatorum, which needs targeted treatment to protect vision and the mother. ^[2]
• Immunocompromised patients. They can develop severe atypical infection and need a lower threshold for referral.
• Red flags for malignancy. Chronic or recurrent conjunctivitis, especially in older patients, can be the first sign of sebaceous carcinoma, lymphoma, or squamous cell carcinoma. ^[9]
• Loss of the corneal reflex, lagophthalmos, or a neurotrophic picture after long-standing redness suggests corneal anaesthesia or facial nerve problems rather than simple inflammation.
• Bilateral, severe pain with headache, nausea, and haloes. Acute angle closure glaucoma is a true emergency that closes vision in hours.

A useful bedside rule: if the patient does not feel well enough to read or work, if the eye hurts in the dark, or if either eye has lost vision, refer the same day.

A focused history takes two minutes and it decides almost everything. Ask in this order so that you follow the red-flag list.

• Pain. Gritty, foreign-body pain fits surface disease; sharp stabs with blinking fit a foreign body or abrasion; a deep ache fits sclera or orbit; colic with nausea fits pressure. Ask whether it hurts more with eye movement.
• Photophobia. Ask specifically, "Does light make it hurt?" It ranks corneal and anterior chamber inflammation above conjunctivitis.
• Vision. Ask exactly: is it the same as the other eye? Reduced vision is the single biggest red flag.
• Discharge. Watery and bilateral suggests viral; thick, mucous, and unilateral suggests bacterial; stringy mucoid suggests allergic; none at all narrows the field to dry eye or inflammation.
• Itch. Itching is the hallmark of allergy. Pain and itch rarely co-exist in the same condition.
• Duration. Hyperacute onset within the first 24 hours covers gonococcal and meningococcal conjunctivitis, severe chemical burns, and trauma. ^[2] Acute processes run up to 4 weeks. Symptoms lasting longer than 4 weeks are chronic and need a systemic or atypical work-up. ^[2]
• Laterality. Bilateral and synchronous points to viral or allergic causes; unilateral onset points to foreign body, trauma, or infection.

• Trauma. Ask about the exact mechanism: fingers, branches, sparks, hammer and chisel, grinding, contact lens, fingernail, splash, industrial chemicals, or animal/plant material.
• Contact lenses. Type, overnight wear, hygiene, recent swim or hot tub, and how long the eye has been painful since removal. This is the key risk factor for microbial keratitis. ^[8]
• Occupation and hobbies. Welders, grinders, agricultural workers, and anyone without eye protection have higher rates of foreign body and chemical injury; corneal foreign bodies make up 30% to 40% of cases seen in emergency ophthalmology settings. ^[4]
• Medication and drops. Current eye drops, preservatives, long-term steroid or immunosuppressant use.
• Systemic disease. Joint pain or back stiffness (HLA-B27-related disease), psoriasis, inflammatory bowel disease, sarcoidosis, Behcet disease, lupus, tuberculosis, or prior ocular surgery. These underlie most non-infectious anterior uveitis and scleritis. ^[6]
• Allergy and atopy. Hay fever, asthma, eczema for allergic conjunctivitis.
• General health. Pregnancy, immunosuppression, diabetes, recent transplant, sleep apnoea (floppy eyelid syndrome with superior limbic keratoconjunctivitis suggests thyroid or sleep apnoea). ^[9]

Ask the patient to compare this redness with anything they have had before, and ask whether it is getting worse, stable, or improving. Chronic or relapsing episodes deserve a broader aetiological search, including chlamydia, ocular surface disease, and systemic inflammation.

Examine in this order so that you never perform a maneuver that worsens the eye before you have seen it naturally.

• Observe the patient before you touch the eye: are they photophobic, blepharospastic, unable to open the eye, or holding it still?
• Note whether the redness is diffuse, sectoral, circumcorneal (ciliary injection around the limbus, which signals deeper disease), or localised to a patch.
• Inspect the lids for swelling, discharge at the lash roots, vesicles, scarring, symblepharon, or incomplete closure.

• Best-corrected or pinhole visual acuity in both eyes. A drop in acuity is the most important finding after the history.

• Look for cells and flare in the anterior chamber by shining a narrow beam across the pupil (a penlight in a darkened room will show them if they are dense).
• Assess the pupil: size, shape, reactivity, and whether it is irregular or stuck to the lens.
• Look for hypopyon, hyphaema, or foreign material.

• Inspect the cornea with magnification and good light. A focal white infiltrate, a dendrite, a round ulcer, or oedema each points to a different organism or mechanism.
• Fluorescein staining with a cobalt blue light or a slit lamp is the single most useful test in the emergency setting. It shows epithelial defects, foreign bodies (which appear as negative shadows), branching dendrites, and roughness.

Fluorescein is harmless and quick. Moisten a sterile fluorescein strip, touch the lower fornix, ask the patient to blink, and examine under blue light. White, green, or yellow areas are epithelial loss. Do not use fluorescein from a dropper bottle if you can avoid it; it is an infection risk.

When one is available, the slit lamp confirms what the torch suggests and adds detail:

• Corneal epithelium, stroma, and endothelium.
• Anterior chamber depth, cells, and flare.
• Iris, pupil margin, and any synechiae.
• Lens clarity.
• Conjunctival fornix, especially for retained foreign material tucked under the upper lid.

Everting the upper lid (a simple cotton bud gently rolled under the lid margin) is mandatory in any suspected foreign body or abrasion. Vegetative and paint-chip material is often trapped high under the upper palpebral conjunctiva.

• Ciliary (circumcorneal) injection: a ring of red around the limbus, seen in acute glaucoma, uveitis, and keratitis.
• Conjunctival injection: diffuse redness of the bulbar conjunctiva, typical of conjunctivitis.
• Episcleral blanching with topical phenylephrine (or an artificial tear or decongestant drop) points to episcleritis (the deeper red of scleritis does not blanch).
• Scleral tenderness: ask the patient to look away and gently press the sclera through the lid; scleritis hurts sharply.
• Intraocular pressure. A raised pressure with a hard globe in a painful red eye is acute glaucoma until proven otherwise. Measure with a tonometer if trained and equipment is available.

• Pre-auricular lymphadenopathy is common in viral conjunctivitis.
• Assess lid closure and corneal exposure in a patient who cannot fully blink (for example after facial nerve palsy or in an intensive care setting). Exposure keratopathy can mimic other red eyes.

Do not order tests before the history and examination have defined the question. The order below starts at the bedside and escalates only as needed.

1. Bedside: visual acuity, torch examination, fluorescein with cobalt blue light. This triad sorts surface disease, foreign body, and anterior chamber inflammation within minutes.
2. Slit lamp biomicroscopy. Confirms the bedside findings and adds depth.
3. Intraocular pressure. Specifically when pain, corneal oedema, haloes, or a shallow anterior chamber are present.
4. Swab or scraping for culture and PCR. Reserved for suspected microbial keratitis, hyperacute (gonococcal) conjunctivitis, unusual or severe disease, or cases that do not respond as expected. Everyday bacterial conjunctivitis does not need a swab before treatment.
5. Imaging. Orbital and sinus radiographs or computed tomography if a retained or deeply penetrating foreign body is suspected, if there has been high-velocity trauma, or if orbital cellulitis is on the differential.
6. Systemic work-up. For recurrent or chronic uveitis and scleritis: full blood count, erythrocyte sedimentation rate and C-reactive protein, HLA-B27 testing guided by symptoms, syphilis and tuberculosis screening, chest imaging when sarcoid is suspected, and a targeted rheumatology referral. ^[6]
7. Aqueous or vitreous tap is an ophthalmology procedure for endophthalmitis and is not a first-line investigation for a red eye.

Normal ranges vary by laboratory, so compare results against the local reference range and confirm unexpected values before acting.

A red eye can be triaged in five questions. The flowchart below is a teaching algorithm, not a substitute for local guidance; involve ophthalmology early when in doubt.

Corneal abrasion is the second most common ocular diagnosis in primary care after conjunctivitis and the commonest eye injury in children and adults attending emergency departments. It accounts for 8% of all eye-related visits in primary care and 12.5% of visits to eye emergency departments in the United Kingdom. ^[8]

Most uncomplicated superficial abrasions heal completely within 3 to 5 days. ^[3] Management is therefore supportive with a low threshold for review:

• Instil a topical anaesthetic drop for examination if a slit lamp is available.
• Remove any loose foreign material with sterile irrigation or a moistened cotton swab; use a sterile needle or burr for an embedded particle only if trained.
• Topical antibiotic prophylaxis is the usual next step. The Cochrane review of 2025 found only very-low-certainty evidence that antibiotics prevent ocular infection or accelerate healing after corneal abrasion; nevertheless, the American Academy of Ophthalmology (AAO) recommends topical antibiotic prophylaxis for contact lens-related abrasions, and the United Kingdom's National Institute for Health and Care Excellence (NICE) Clinical Knowledge Summaries and the College of Optometrists recommend considering a broad-spectrum antibiotic (chloramphenicol is a common example) when there is a risk of infection, with specific gram-negative cover (a fluoroquinolone or an aminoglycoside) for contact lens wearers. ^[8]
• Cycloplegic drops (such as cyclopentolate) reduce ciliary spasm pain in large abrasions; some have questioned their benefit, so use them for symptom control rather than routine. ^[8]
• Topical non-steroidal anti-inflammatory drops can help pain. Evidence for them is at best moderate. ^[8]
• Small abrasions (less than 10 mm) are no longer routinely patched; ophthalmologists still patch large abrasions in adults and abrasions in children. ^[8]
• Review promptly if the abrasion has not healed, if pain persists, or if the patient wears contact lenses.
• Advise no contact lenses until the epithelium has fully healed and the eye is quiet for at least a day or two, and give a clear return protocol for increasing pain, decreasing vision, or new discharge.
• Give analgesia and explain the expected 3- to 5-day course so the patient is not alarmed by initial foreign body sensation. ^[3]

Check the product labels and local formulary for exact concentrations and for age restrictions in children; names, strengths, and availability differ between countries.

Corneal foreign bodies are the second most common cause of ocular trauma after corneal abrasions and account for 30% to 40% of cases in emergency ophthalmology settings. They are particularly common among industrial workers, welders, and agricultural labourers without adequate eye protection. ^[4]

• Remove the foreign body under topical anaesthesia with slit lamp guidance where possible; use a sterile needle or burr only when trained.
• Always evert the upper lid to look for a retained fragment.
• Rust rings from metallic foreign bodies should be debrided to prevent persistent inflammation.
• After removal, treat as an abrasion: topical antibiotic, cycloplegia if needed, and review. Organic (vegetative) foreign bodies carry the highest infection risk and should be treated with a lower threshold for referral and closer follow-up. ^[4]
• Consider imaging (anterior segment optical coherence tomography, X-ray, or computed tomography) for deeper or radiopaque material, and note that posterior segment complications such as traumatic uveitis, vitreous haemorrhage, or endophthalmitis can occur if the object penetrated beyond the cornea. ^[4]
• Tetanus prophylaxis should follow local trauma policy for plant and soil-contaminated injuries.

Acute chemical burns are true ophthalmic emergencies. Alkali burns are particularly severe because these lipophilic substances penetrate rapidly through the corneal epithelium and stroma into deeper structures; acids tend to produce coagulative necrosis that may limit deeper penetration but can still cause extensive surface damage. ^[5]

Immediate steps, in order:

1. Irrigate immediately and copiously at the point of injury. Normal saline or any clean water available is appropriate; the critical factor is starting now, not finding the perfect solution. Continue until the ocular surface pH normalises if pH paper is available.
2. Hold the lids open and sweep the fornices to remove particulate chemical trapped under them.
3. Topical anaesthetic drops allow tolerance of continued irrigation.
4. Document the chemical agent, concentration, and duration of exposure for the receiving hospital.
5. Arrange same-day ophthalmology review; copious irrigation and pH normalisation influence final outcome more than the agent itself. ^[5]
6. Subsequent care, delivered by ophthalmology, follows a staged path: intensive lubrication, topical corticosteroids and cycloplegics, intraocular pressure control, and adjuncts such as ascorbate or citrate for stromal integrity; severe injuries may need amniotic membrane transplantation or later surface reconstruction. ^[5]

Do not delay irrigation to take a detailed history; the history can be completed on the way to or once irrigation has started.

Anterior uveitis, also called iritis, is the most common form of uveitis. Acute anterior uveitis (AAU) is the most common clinical presentation, and HLA-B27-related and idiopathic disease are the most common causes. ^[6] It classically presents as a painful red eye with photophobia, tearing, and a small or irregular pupil; cells and flare in the anterior chamber are the diagnostic sign.

• Definitive diagnosis and treatment belong to ophthalmology. Initial measures performed at presentation include a very careful slit lamp examination, intraocular pressure measurement, and urgent referral.
• Under ophthalmology care, topical corticosteroids and a dilating drop (cycloplegia) are the mainstays; cycloplegia relieves ciliary spasm and prevents posterior synechiae. Steroid choice and taper are individualised and are not a general practitioner first step.
• Chronic anterior uveitis is usually bilateral and secondary to an underlying systemic pathology, so a young patient with recurrent unilateral attacks raises HLA-B27 spondyloarthritis, while bilateral chronic disease raises sarcoidosis, tuberculosis, Behcet disease, or juvenile idiopathic arthritis. ^[6]
• Most idiopathic and HLA-B27-related AAU has a good prognosis if managed adequately. ^[6]
• Scleritis is a severe, potentially vision-threatening inflammation of the sclera. It may present as diffuse, nodular, or necrotising anterior scleritis, or as posterior scleritis. ^[7]
• Differentiating immune-mediated scleritis from infectious scleritis is critical: corticosteroids and other immunosuppressants, the mainstays of immune-mediated disease, can worsen uncontrolled infection and delay correct antimicrobial therapy. ^[7]
• Infectious scleritis accounts for 5% to 10% of all scleritis cases and tends to follow prior ocular surgery, trauma, scleral necrosis, or purulence, or to progress despite corticosteroids. ^[7]
• Scleritis is an ophthalmology and often rheumatology condition: arrange same-day review, control pain, and do not start topical steroids until infection has been excluded.

Conjunctivitis is the most common red eye and the one most often managed outside ophthalmology. The classification matters more than any single treatment, because viral, bacterial, allergic, and toxic disease are managed differently.

• Viral is the most common overall cause. ^[10] It usually presents with watery discharge, bilateral involvement, lid swelling, and a pre-auricular node; adenoviral infection is highly contagious, and patients should be counselled on hygiene during the period of contagion, which is usually 10 to 14 days from onset. ^[9]
• Bacterial is the second most common cause of infectious conjunctivitis and accounts for 78% of paediatric acute cases; adults more often have viral or allergic disease, but a significant proportion is still bacterial. Acute bacterial conjunctivitis runs up to 4 weeks. ^[2] Mild bacterial conjunctivitis is likely to be self-limited, so indiscriminate antibiotics should be avoided. ^[9]
• Allergic conjunctivitis occurs in nearly half of the population; the defining feature is intense itching with mucoid discharge, chemosis, and lid swelling. ^[10]
• Hyperacute conjunctivitis (gonococcal or meningococcal) presents within the first 24 hours with severe symptoms and is a vision-threatening emergency requiring immediate systemic therapy. ^{[2] [9]}
• Toxic or medication-related conjunctivitis follows long-term use of preserved eye drops in a patient with chronic irritation and discharge and improves when the product is withdrawn.
• Chronic or recurrent conjunctivitis in an older patient should prompt examination for underlying malignancy (sebaceous carcinoma, lymphoma, squamous cell carcinoma), inflammatory disease (mucous membrane pemphigoid), or chronic infection (chlamydia). ^[9]
• Conjunctivitis caused by herpes zoster requires special care; herpes zoster vaccination is strongly recommended in patients 50 years and older and in immunocompromised patients 19 years and older. ^[9]
• Gonococcal ophthalmia neonatorum is prevented by single-use tubes of 0.5% erythromycin ophthalmic ointment. ^[9]
• Disinfection matters in the clinic: dilute sodium hypochlorite at a 1:10 concentration is effective for tonometers, while 70% isopropyl alcohol, 3% hydrogen peroxide, and ethyl alcohol are no longer recommended. ^[9]

For detailed pathogen-level management, cross-check the Infectious Disease topics on bacterial, viral, and sexually transmitted conjunctivitis.

• Same day to ophthalmology: any reduced vision; chemical or penetrating injury; suspected microbial keratitis (infiltrate, ulcer, hypopyon); acute glaucoma; sight-threatening uveitis with high pressure; scleritis; orbital cellulitis; gonococcal conjunctivitis; and any neonatal conjunctivitis. ^[6][7][9]
• Urgent (next few days): foreign body not removable at the bedside; abrasion that is not healing; uncontrolled pain; contact lens-related abrasion for review even if initially treated; suspected malignancy or chronic conjunctivitis; recurrent uveitis needing systemic work-up.
• Routine: confirmed viral or allergic conjunctivitis responding to treatment; episcleritis; uncomplicated blepharitis; dry eye; post-operative review of a healed abrasion.
• When you are unsure whether something is "just conjunctivitis", the safest rule is to treat it as red flag until examined. A short note in the referral with acuity, pain score, and whether a contact lens was worn saves time for the receiving team.

• Children. 78% of acute paediatric infectious conjunctivitis is bacterial. ^[2] Neonates in the first 4 weeks of life require a distinct work-up for ophthalmia neonatorum. Corneal abrasions in children are often patched to prevent amblyopia-risking exposure; foreign bodies in children are usually superficial and can be removed under distraction.
• Contact lens wearers. Any painful red eye in a lens wearer is microbial keratitis until proven otherwise. Remove the lens immediately, start an antibiotic with gram-negative cover, and arrange urgent ophthalmology review. ^[8]
• Older adults. Think of underlying malignancy with chronic unilateral redness, giant cell arteritis with scalp and jaw symptoms alongside a red tender eye, and herpes zoster with cranial nerve involvement.
• Immunocompromised readers. They may present with atypical infection, herpetic keratitis, or unusual organisms; thresholds for referral and culture are low.
• Pregnancy. Systemic treatment decisions (for example anti-inflammatory agents and some antimicrobials) need obstetric input; topical therapy is preferred and doses chosen with pregnancy in mind. Local formularies and specialist advice should be checked.
• Low-resource settings. Bedside examination skills matter more than equipment: fluorescein, a cotton bud, and a penlight triage most red eyes, and irrigation with clean water saves alkali-burned eyes. ^[5] Occupational eye protection programmes reduce foreign body incidence, which is highest where safety measures are inadequate. ^[4] Beware of amplifying disadvantage: patients who cannot reach an ophthalmologist need a clear, written plan and a named place and date to return to.

• Calling every red eye "conjunctivitis". It is the most common diagnosis, which is exactly why it is misdiagnosed.
• Treating a contact lens-related abrasion like an everyday scratch; that is the group most at risk of microbial keratitis. ^[8]
• Prescribing topical corticosteroids for an undifferentiated red eye. Steroids can worsen herpetic keratitis, fungal infection, and microbial keratitis, and they delay the correct therapy. ^[7] If the diagnosis is uncertain, refer rather than start a steroid.
• Forgetting to evert the upper lid; a hidden foreign body makes the eye worse no matter how well you treat the abrasion.
• Missing a retained corneal foreign body rust ring; the eye never settles until it is debrided.
• Taping an eye shut without first ruling out infection or an ingested chemical; occlusion can worsen both.
• Not checking intraocular pressure in a painful red eye; acute angle closure presents late and fast.
• Assuming that a red eye with no pain and normal vision is always benign; subconjunctival haemorrhage is benign, but episcleral or deep injection, a fixed pupil, or new onset after 40 should make you look closer.
• Ignoring the systemic clues: back pain, joint swelling, mouth ulcers, and cough each change the uveitis or scleritis differential.
• Relying on eye drops borrowed from a friend or another patient; preservatives and wrong antibiotics cause toxic conjunctivitis. ^[10]

• A red eye is not a diagnosis; it is a symptom with a structured differential by anatomical site and threat to sight.
• Reduced vision, severe or night-time pain, photophobia, and a fixed or irregular pupil are the universal red flags.
• Conjunctivitis is the commonest cause (about 3% of general medical visits) but it is a diagnosis of exclusion after sight-threatening causes have been considered. ^[2]
• Watery, bilateral, itchy, or mucoid discharge point at viral, allergic, or toxic conjunctivitis; each has a different treatment and a different contagion message.
• Bacterial conjunctivitis accounts for 78% of paediatric acute infectious cases; mild cases are self-limited, so avoid indiscriminate antibiotics. ^[2][9]
• Corneal abrasion: pain and photophobia, epithelial defect on fluorescein, heals in 3 to 5 days; small abrasions (less than 10 mm) are no longer routinely patched. ^[3][8]
• Contact lens wearers with a painful red eye are high-risk for microbial keratitis and need urgent gram-negative cover and ophthalmology review. ^[8]
• Corneal foreign bodies make up 30% to 40% of emergency ophthalmology cases and carry the highest risk when organic. ^[4]
• Alkali chemical burns are the most dangerous ocular burns because they keep penetrating; irrigation starts immediately. ^[5]
• Anterior uveitis is the commonest uveitis and usually presents with pain, photophobia, and a small pupil; HLA-B27 and idiopathic disease dominate. ^[6]
• Scleritis is deep and night-waking; exclude infection before using corticosteroids. ^[7]
• Always check acuity, always examine the cornea with fluorescein, and always evert the upper lid.
• Rule out malignancy in chronic or recurrent adult conjunctivitis. ^[9]
• Coordinate care early with ophthalmology and rheumatology when uveitis or scleritis is present.

• Conjunctivitis (Infectious Disease): bacterial, viral, chlamydial and hyperacute causes and their treatments.
• Corneal ulcer and microbial keratitis: diagnosis, sampling and therapy.
• Acute glaucoma: recognition and emergency management of raised intraocular pressure.
• Uveitis (Rheumatology and Immunology): HLA-B27 disease, sarcoidosis, Behcet disease.
• Orbital cellulitis: red flags, imaging and antibiotics.
• Ocular trauma: foreign body, penetrating injury and hyphaema.

Numbers, thresholds and treatment recommendations on this page are drawn from the sources below, including the StatPearls chapters where cited, the Cochrane review on antibiotic prophylaxis for corneal abrasion, the American Academy of Ophthalmology (AAO) Preferred Practice Pattern "Conjunctivitis PPP 2023" (published February 2024), and the systematic review by Azari and Arabi on conjunctivitis. National guidelines such as NICE Clinical Knowledge Summaries and Royal College of Ophthalmologists guidance are widely used for red eye management; local editions and formularies should be checked before applying any of the above to a specific patient. Drug names and strengths vary between countries, and all doses should be confirmed against the local formulary.