Special Senses & Otolaryngology

Painful red eye: differential and triage

Clinical Overview and When to Suspect a Dangerous Red Eye

— Acute angle-closure glaucoma (AACG): mid-dilated fixed pupil, rock-hard globe, halos, nausea

— Bacterial keratitis / corneal ulcer: contact lens wearer, white corneal infiltrate, fluorescein uptake

— Anterior uveitis (iritis): photophobia, ciliary flush, miotic poorly reactive pupil, hypopyon

— Endophthalmitis: post-op or post-injection, hypopyon, profound vision loss

— Scleritis: deep boring pain that wakes patient, bluish hue, associated with RA/GPA

— Herpetic keratitis (HSV/VZV): dendritic ulcer, vesicles, hypoesthetic cornea

— Orbital cellulitis: proptosis, pain with EOM, fever

— Chemical burn: requires irrigation before history-taking

— Decreased visual acuity

— Severe deep pain or photophobia

— Ciliary (perilimbal) flush

— Corneal opacity, hypopyon, or hyphema

— Fixed or irregular pupil

— Recent ocular surgery, trauma, or contact lens use

— Immunocompromise

Step 3 management: In an ambulatory clinic, the first triage question is "Is vision affected?" — if yes, treat as emergent and arrange ophthalmology evaluation the same day. The second is "Is the pain deep or superficial?" — deep boring pain suggests sclera/uvea/glaucoma; gritty surface pain suggests conjunctiva/cornea.

Board pearl: A red eye with normal visual acuity, no photophobia, no ciliary flush, and reactive pupils is overwhelmingly benign — usually viral or allergic conjunctivitis manageable in primary care without referral.

The "painful red eye" is a primary care triage problem: most causes are benign (viral conjunctivitis, dry eye, subconjunctival hemorrhage), but a handful are sight-threatening emergencies that must be identified within minutes of presentation.

Vision-threatening diagnoses to actively rule out at every red-eye visit:

Red flags that mandate same-day ophthalmology referral:

Presentation Patterns and Key History

— Onset and laterality: hyperacute (<24 h, copious purulent discharge) → gonococcal; acute unilateral with halos/nausea → AACG; bilateral itchy → allergic; bilateral gritty with URI → viral

— Vision change: any reduction = emergency until proven otherwise

— Pain quality: foreign-body sensation (corneal abrasion, keratitis), deep boring (scleritis, uveitis), throbbing with nausea (AACG), itch (allergy — itch is the cardinal allergic symptom)

— Discharge: purulent/sticky lids → bacterial; watery → viral; stringy mucoid → allergic or dry eye

— Photophobia: strongly suggests corneal or intraocular pathology (keratitis, uveitis), not conjunctivitis

— Contact lens use: extended wear, sleeping in lenses, or swimming in lenses → assume Pseudomonas keratitis until disproven

— Trauma/foreign body: grinding metal without eye protection → suspect intraocular foreign body, get CT (not MRI)

— Chemical exposure: alkali burns (lye, ammonia, cement) are worse than acid — irrigate first

— Recent eye surgery or intravitreal injection: endophthalmitis until proven otherwise

— Systemic disease: RA, IBD, ankylosing spondylitis, sarcoid, syphilis, TB → uveitis/scleritis; GPA → scleritis; HIV → CMV retinitis, HZO

— Cold sores or dermatomal vesicles: HSV/VZV keratitis (Hutchinson sign — tip-of-nose vesicle predicts ocular involvement)

Key distinction: Itch = allergy. Pure conjunctival redness without itch, photophobia, vision change, or pain is almost always viral or bacterial conjunctivitis. Pain + photophobia + vision change flips the differential to cornea/uvea/glaucoma.

Board pearl: A neonate with red eye and purulent discharge in the first 24 hours → chemical (silver nitrate, now rare); day 2–5 → gonococcal (urgent IV/IM ceftriaxone, hospitalize); day 5–14 → chlamydial (oral erythromycin, treat mother).

A focused history sorts 80% of red eyes before the slit lamp. Ask in this order:

Physical Exam Findings and Bedside Assessment

— Visual acuity (Snellen, each eye separately, with correction) — the single most important vital sign of the eye

— External inspection: lid swelling, vesicles, proptosis, ptosis

— Pupils: size, symmetry, reactivity, RAPD (afferent pupillary defect suggests optic nerve or large retinal disease)

— Extraocular movements: pain with EOM → orbital cellulitis or scleritis

— Pattern of redness:

– Diffuse bulbar injection sparing limbus → conjunctivitis

– Ciliary flush (perilimbal injection) → keratitis, uveitis, AACG

– Sectoral deep violaceous → scleritis (does not blanch with phenylephrine; episcleritis does blanch)

— Fluorescein staining under cobalt blue light:

– Linear/punctate uptake → abrasion

– Dendritic pattern → HSV keratitis (avoid topical steroids!)

– Geographic ulcer with infiltrate → bacterial keratitis

– Seidel sign (streaming aqueous) → globe perforation

— Intraocular pressure (Tono-Pen or iCare): normal 10–21 mmHg; >30 with red painful eye and mid-dilated pupil → AACG

— Cornea: clarity, infiltrates, hypopyon (layered pus in anterior chamber)

— Lid eversion: mandatory if foreign body sensation persists

CCS pearl: Order "visual acuity, pupillary exam, fluorescein stain, intraocular pressure measurement" on any painful red eye — these four steps are the standard initial workup and are individually orderable on the CCS interface.

Board pearl: A hard globe on palpation with cloudy cornea and mid-dilated nonreactive pupil = AACG — do not wait for tonometry, call ophthalmology immediately and start pressure-lowering drops.

Key distinction: Episcleritis (mild, blanches with phenylephrine, self-limited) vs scleritis (severe boring pain, bluish, does not blanch, systemic disease workup mandatory).

Every red-eye exam in primary care should include, in order:

Diagnostic Workup — Initial Office Studies

— Anterior chamber cell and flare → uveitis

— Corneal infiltrate → bacterial keratitis (culture before treating if vision-threatening, central, or large)

— Dendrites → HSV (rose bengal enhances)

— Mandatory in any deep eye pain, halos, nausea, or mid-dilated pupil

— Also elevated in uveitic glaucoma and traumatic hyphema

— Indicated for contact lens–associated ulcers, ulcers >1–2 mm, central ulcers, or those unresponsive to empiric therapy

— Gonococcal conjunctivitis: Gram stain shows gram-negative intracellular diplococci — culture on Thayer-Martin

— Chlamydia/gonorrhea if hyperacute or chronic follicular conjunctivitis

— Adenovirus PCR or rapid antigen (RPS Adeno Detector) for outbreak settings

— CBC, ESR/CRP, ANA, RF, HLA-B27, ACE, lysozyme, RPR/FTA-ABS, QuantiFERON, ANCA, CXR

— CT orbit (without contrast initially, with contrast if cellulitis): suspected orbital cellulitis, intraocular foreign body, trauma with possible globe rupture

— MRI: optic neuritis, posterior scleritis (avoid if metallic FB suspected)

— B-scan ultrasound: when cornea is opaque and posterior segment can't be visualized

Step 3 management: A primary care clinician seeing suspected gonococcal conjunctivitis should obtain conjunctival swab for Gram stain/culture/NAAT, co-test for chlamydia, treat empirically with IM ceftriaxone 1 g plus oral doxycycline (or azithromycin if pregnant), and arrange same-day ophthalmology for saline lavage.

Board pearl: Never patch a contact-lens-associated corneal abrasion — risk of Pseudomonas keratitis. Treat with topical fluoroquinolone and follow daily.

Most painful red eyes are diagnosed clinically; targeted ancillary testing is reserved for specific scenarios.

Slit-lamp examination (or office equivalent with fluorescein + cobalt light):

Tonometry:

Cultures and Gram stain (corneal scraping by ophthalmology):

Conjunctival swab PCR:

Systemic labs for uveitis/scleritis (per ophthalmology, after ≥2 episodes or bilateral disease):

Imaging:

Diagnostic Workup — Advanced and Confirmatory Studies

— Confocal microscopy detects Acanthamoeba cysts (contact lens wearer with severe pain out of proportion to findings, ring infiltrate) and fungal hyphae (vegetative trauma)

— HLA-B27 → ankylosing spondylitis, reactive arthritis, IBD, psoriatic

— Sarcoid → ACE, lysozyme, CXR, chest CT, biopsy

— Syphilis → RPR + treponemal test (uveitis is a manifestation of neurosyphilis → LP, IV penicillin)

— TB → IGRA, CXR

— Behçet → clinical (oral/genital ulcers, hypopyon uveitis)

Board pearl: Acanthamoeba keratitis = contact lens wearer + tap water/swimming exposure + pain out of proportion + ring infiltrate. Diagnose with confocal microscopy; treat with biguanides (PHMB) and diamidines for months.

Key distinction: A positive syphilis serology in a uveitis patient mandates LP and treatment as neurosyphilis regardless of CSF findings — ocular syphilis is neurosyphilis by definition.

Advanced testing is largely ophthalmology-directed but the primary care board examinee should recognize indications and interpret results.

Gonioscopy: confirms narrow/closed angle in AACG; performed once IOP is controlled. Distinguishes primary angle closure from open-angle mechanisms (neovascular, uveitic).

Anterior segment OCT: rapid, non-contact imaging of angle anatomy; helpful when gonioscopy is impractical.

Corneal cultures and confocal microscopy:

Anterior chamber paracentesis with PCR: viral uveitis (CMV, HSV, VZV), endophthalmitis pathogen identification.

Vitreous tap and inject (endophthalmitis): diagnostic and therapeutic — intravitreal vancomycin + ceftazidime; the EVS trial showed pars plana vitrectomy benefits only patients with light-perception-only vision.

B-scan ultrasonography: posterior scleritis (T-sign from fluid in Tenon's capsule), endophthalmitis, retinal detachment behind opaque media.

Fluorescein angiography / OCT: when uveitis involves posterior segment.

Systemic workup for recurrent or bilateral uveitis:

Scleritis workup: GPA (c-ANCA/PR3), RA, relapsing polychondritis, IBD; necrotizing scleritis with adjacent corneal melt is sight- and life-threatening (vasculitis marker).

Risk Stratification and Triage Logic

— Tier 1 — Emergency, refer now (minutes to hours):

– Acute angle-closure glaucoma

– Chemical burn (irrigate first, then refer)

– Globe rupture / penetrating trauma (shield, NPO, antiemetics, IV antibiotics, no pressure on globe)

– Endophthalmitis

– Orbital cellulitis

– Bacterial keratitis with central ulcer or contact lens use

– Hyperacute (gonococcal) conjunctivitis

— Tier 2 — Urgent, same-day or next-day ophthalmology:

– Anterior uveitis

– Scleritis

– HSV/VZV keratitis (HZO with Hutchinson sign)

– Corneal abrasion in contact lens wearer

– Hyphema (microhyphema can be outpatient; larger needs IOP monitoring)

— Tier 3 — Manage in primary care:

– Viral conjunctivitis (supportive, cold compress, hygiene to prevent spread; highly contagious 10–14 days)

– Bacterial conjunctivitis (topical antibiotic; most cases self-limited)

– Allergic conjunctivitis (topical antihistamine/mast cell stabilizer, e.g., olopatadine)

– Subconjunctival hemorrhage (reassure, check BP and anticoagulation)

– Dry eye / blepharitis (warm compresses, lid hygiene, artificial tears)

– Simple corneal abrasion in non–contact lens wearer (topical antibiotic, no patching, oral analgesics; avoid topical anesthetics for home use — toxic to cornea)

– Pterygium/pinguecula irritation

Step 3 management: For chemical burn, irrigate with at least 1–2 L of normal saline or LR over 30 minutes, recheck pH every 5 minutes after irrigation until neutral (7.0–7.4), then refer. Do not delay irrigation for visual acuity or history.

Board pearl: A red eye with systemic joint symptoms narrows to HLA-B27 uveitis, reactive arthritis ("can't see, can't pee, can't climb a tree"), or scleritis in RA/GPA — order ESR/CRP and refer.

The Step 3 triage decision tree for painful red eye:

Pharmacotherapy — First-Line Treatment by Diagnosis

— Erythromycin 0.5% ointment QID or polymyxin B–trimethoprim drops QID × 5–7 days

— Most cases self-resolve; antibiotics shorten course modestly

— Topical fluoroquinolone (moxifloxacin, ciprofloxacin, besifloxacin) every 1–2 hours initially — covers Pseudomonas

— Discontinue lenses; daily ophthalmology follow-up

— Topical timolol, brimonidine, pilocarpine 1–2% (once IOP <40), prednisolone

— Oral or IV acetazolamide 500 mg

— IV mannitol if refractory

Step 3 management: For suspected bacterial keratitis in a contact lens user, start moxifloxacin 0.5% every hour around the clock and refer same day — do not wait for cultures. Stop lens wear; discard the case and lenses.

Board pearl: Topical anesthetics (proparacaine, tetracaine) are diagnostic only — never prescribe for home use; they cause corneal melting.

Bacterial conjunctivitis (non–contact lens):

Bacterial conjunctivitis in contact lens wearer or suspected keratitis:

Gonococcal conjunctivitis: IM ceftriaxone 1 g (adults), saline lavage, treat partner, co-treat chlamydia (doxycycline 100 mg BID × 7 days)

Chlamydial conjunctivitis (adult inclusion): oral doxycycline 100 mg BID × 7 days or azithromycin 1 g single dose

Viral conjunctivitis: supportive — cold compresses, artificial tears, strict hand hygiene, no school/work while tearing/discharge present

Allergic conjunctivitis: olopatadine 0.2% daily or ketotifen BID; cold compresses; avoid rubbing

HSV epithelial keratitis: oral acyclovir 400 mg 5×/day or valacyclovir 500 mg TID × 7–10 days, or topical trifluridine/ganciclovir gel; never topical steroids without ophthalmology

HZO (herpes zoster ophthalmicus): oral valacyclovir 1 g TID × 7 days, start within 72 hours of rash; ophthalmology evaluation

Anterior uveitis: topical prednisolone acetate 1% q1–2h + cycloplegic (cyclopentolate or homatropine) for comfort and to prevent synechiae — initiated by ophthalmology

Acute angle-closure glaucoma (initial medical therapy while awaiting laser iridotomy):

Procedures and Definitive Management

— Laser peripheral iridotomy (LPI) on the affected eye once cornea clears

— Prophylactic LPI on the fellow eye (anatomically predisposed)

— Cataract extraction may be definitive in phacomorphic angle closure

— Vitreous tap with intravitreal vancomycin + ceftazidime (or amikacin)

— Pars plana vitrectomy if light perception only (EVS trial)

— Topical fortified antibiotics and cycloplegic adjuvants

— Admit, IV vancomycin + ceftriaxone (± metronidazole for sinus source)

— CT orbits/sinuses; ENT consult for sinus drainage if subperiosteal abscess >10 mm or no improvement at 48 h

— Surgical drainage indications: abscess, vision loss, no improvement

— Fox shield, no patching, no IOP measurement, no topical drops

— NPO, antiemetics, IV cefazolin (+ fluoroquinolone for organic matter), tetanus

— Emergent surgical repair within 24 hours

CCS pearl: For orbital cellulitis in CCS, order CT orbits with contrast, blood cultures, CBC, IV vancomycin, IV ceftriaxone, ophthalmology consult, ENT consult, admit to ward, and advance the clock 24 h before reassessing.

Board pearl: A sickle cell patient with hyphema is at high risk of secondary IOP rise and optic atrophy — avoid acetazolamide and mannitol; consider early surgical washout.

Acute angle-closure glaucoma — definitive treatment:

Bacterial keratitis: fortified topical antibiotics (vancomycin + tobramycin or cefazolin + tobramycin) every hour; therapeutic penetrating keratoplasty for perforation

Endophthalmitis:

Orbital cellulitis:

Globe rupture:

Hyphema: head of bed 30°, shield, topical steroids and cycloplegic, IOP monitoring; screen for sickle cell trait/disease in Black patients (avoid carbonic anhydrase inhibitors and hyperosmotics — promote sickling in AC)

Chemical burn: copious irrigation, debride retained particles, topical antibiotics + steroids + cycloplegic + ascorbate; amniotic membrane for severe alkali injury

Corneal foreign body: removal under slit lamp with 25-gauge needle or burr, then topical antibiotic and follow-up

HZO complications: oral antivirals + topical steroids (under ophthalmology) for stromal/uveitic involvement

Special Populations — Elderly and Renal/Hepatic Impairment

— Acute angle-closure glaucoma: hyperopic, female, Asian ancestry, shallow anterior chamber; precipitated by dim light, anticholinergics, sympathomimetics, topiramate

— Giant cell arteritis (GCA) presenting as eye pain with jaw claudication, scalp tenderness, AAION (pale swollen disc), elevated ESR/CRP — start high-dose IV methylprednisolone before biopsy if suspected

— Herpes zoster ophthalmicus: incidence rises sharply >50; shingles vaccine (Shingrix) recommended ≥50, two doses 2–6 months apart, including in immunocompromised

— Dry eye and blepharitis: more common; can mimic chronic conjunctivitis

— Bullous pemphigoid / ocular cicatricial pemphigoid: symblepharon, chronic redness

— Anticholinergics, decongestants, TCAs, SSRIs, topiramate, sulfa drugs → can precipitate angle closure

— Bisphosphonates → uveitis/scleritis (rare but reported)

— Tamsulosin → intraoperative floppy iris syndrome (relevant for cataract surgery referral)

— Acetazolamide for AACG: reduce dose if CrCl <50; avoid if CrCl <10; monitor potassium and acidosis

— Valacyclovir/acyclovir for HZO: renally dose to avoid neurotoxicity and crystal nephropathy

— Aminoglycosides (fortified tobramycin) systemic absorption is minimal but caution if open globe

— Avoid NSAIDs for ocular pain in advanced CKD

— Systemic fluoroquinolones: caution with hepatotoxicity and QT prolongation

— Doxycycline preferred over erythromycin/azithromycin in cholestatic disease

— Acetaminophen ≤2 g/day in cirrhosis for ocular pain

Step 3 management: Any patient ≥50 with new headache, jaw claudication, and any visual symptom → check ESR and CRP immediately, start oral prednisone 1 mg/kg (or IV methylprednisolone 1 g if vision loss), and arrange temporal artery biopsy within 1–2 weeks. Do not delay steroids for biopsy.

Board pearl: Painless monocular vision loss in an elderly patient is not in this differential — but painful eye with vision loss + systemic symptoms over age 50 should always trigger GCA workup.

Elderly patients carry a higher prior probability of:

Polypharmacy considerations:

Renal impairment:

Hepatic impairment:

Special Populations — Pregnancy, Pediatrics, and Immunocompromised

— Avoid topical/oral fluoroquinolones when alternatives exist; tetracyclines contraindicated after first trimester

— Erythromycin ophthalmic, polymyxin-trimethoprim, azithromycin, and penicillins/cephalosporins are safe

— Chlamydial conjunctivitis: azithromycin 1 g (doxycycline contraindicated)

— Gonococcal: IM ceftriaxone safe

— Acyclovir/valacyclovir: category B, used for HSV/HZO when needed

— Avoid prostaglandin analogs (latanoprost) for glaucoma — use brimonidine in 2nd/3rd trimester (avoid near term); timolol with neonatal monitoring

— Day 1: chemical (silver nitrate, now rare with erythromycin prophylaxis)

— Day 2–5: gonococcal — IM/IV ceftriaxone single dose 25–50 mg/kg (max 125 mg), hospitalize, evaluate for disseminated disease; saline irrigation

— Day 5–14: chlamydial — oral erythromycin 50 mg/kg/day × 14 days (risk of pyloric stenosis — counsel parents); treat mother and partner

— Day 6+: HSV — IV acyclovir, ophthalmology, evaluate for disseminated/CNS disease

— Periorbital (preseptal) vs orbital cellulitis: orbital has proptosis, pain with EOM, ophthalmoplegia, vision change → CT and IV antibiotics

— Pediatric uveitis: JIA-associated is often asymptomatic and white — mandates scheduled slit-lamp screening regardless of redness

— Kawasaki disease: bilateral nonexudative conjunctival injection, fever ≥5 days, rash, strawberry tongue, cervical adenopathy, extremity changes → IVIG + aspirin

— CMV retinitis (usually painless but can cause secondary inflammation)

— Fungal keratitis and endophthalmitis (Candida, Aspergillus)

— Severe HZO with risk of CNS dissemination — admit for IV acyclovir if disseminated

Board pearl: Universal erythromycin 0.5% ophthalmic ointment is given to all newborns in the US to prevent gonococcal ophthalmia (state law in most states — refusal requires documentation).

Step 3 management: Bilateral conjunctivitis with fever and rash in a child ≥5 days → think Kawasaki, not "pink eye" — get CBC, CRP, ESR, echo, and admit.

Pregnancy:

Neonatal conjunctivitis (ophthalmia neonatorum) — timeline-based:

Pediatric:

Immunocompromised (HIV, transplant, chemotherapy):

Complications and Adverse Outcomes

— AACG: optic nerve infarction within hours of sustained IOP >40–50 mmHg; irreversible if untreated >24 h

— Bacterial/fungal keratitis: corneal scarring, perforation, endophthalmitis, need for keratoplasty

— Endophthalmitis: retinal necrosis, phthisis bulbi, enucleation

— Orbital cellulitis: cavernous sinus thrombosis, intracranial extension, meningitis, brain abscess, optic neuropathy

— HSV keratitis: stromal scarring, neurotrophic ulcer, recurrent disease

— HZO: post-herpetic neuralgia, neurotrophic keratitis, secondary glaucoma, chronic uveitis, contralateral hemiparesis (zoster vasculopathy)

— Uveitis: posterior synechiae → secondary glaucoma; cystoid macular edema; band keratopathy; cataract (both from disease and from steroid therapy)

— Scleritis: scleral melt, peripheral ulcerative keratitis, perforation; necrotizing scleritis has 25% 5-year mortality from associated systemic vasculitis

— Chemical burn: limbal stem cell deficiency, symblepharon, corneal neovascularization

— Hyphema: rebleed (day 2–5), corneal blood staining, glaucoma, optic atrophy (especially in sickle disease)

— Inappropriate topical steroids in undiagnosed HSV → geographic ulcer, perforation

— Topical anesthetic abuse → corneal melt

— Eye patching of contact lens abrasion → Pseudomonas keratitis

— Missed globe rupture from pressure on the eye during exam

— Disseminated gonococcal infection: tenosynovitis, dermatitis, arthritis

— Cavernous sinus thrombosis from orbital/sinus infection: cranial nerve palsies (III, IV, V1–V2, VI), bilateral eye findings

Key distinction: Anterior uveitis causes direct AND consensual photophobia (light in unaffected eye causes pain in affected eye) due to ciliary spasm — this distinguishes it from conjunctivitis-related photophobia.

Board pearl: Loss of corneal sensation in a quiet eye after HSV/HZO = neurotrophic keratitis — high risk of breakdown; needs lubrication, punctal plugs, possibly tarsorrhaphy or cenegermin.

Vision loss is the unifying feared outcome; mechanisms vary by diagnosis:

Iatrogenic complications:

Systemic complications:

When to Escalate Care — Consultation and Inpatient Triage

— Acute angle-closure glaucoma

— Suspected bacterial, fungal, or Acanthamoeba keratitis

— Endophthalmitis (post-op, post-injection, or endogenous)

— Globe rupture or penetrating trauma

— Chemical burn (after initial irrigation)

— Hyphema, especially with elevated IOP or in sickle cell patient

— Anterior uveitis (first episode or severe)

— Scleritis

— HZO with eye involvement

— Hyperacute (gonococcal) conjunctivitis

— Orbital cellulitis (always admit for IV antibiotics)

— Endophthalmitis

— Necrotizing scleritis (admit for systemic immunosuppression workup)

— Disseminated gonococcal infection

— Pediatric preseptal cellulitis with toxicity, age <1 year, or inability to take POs

— Severe alkali burn requiring continuous irrigation

— Suspected GCA with vision loss (IV methylprednisolone)

— Neonatal HSV or gonococcal conjunctivitis

— ENT: sinusitis-driven orbital cellulitis with abscess

— Neurosurgery / IR: cavernous sinus thrombosis

— Rheumatology: scleritis or uveitis with systemic vasculitis (GPA, RA)

— ID: endogenous endophthalmitis (consider IV drug use, bacteremia, endocarditis — get blood cultures and TTE)

— Pediatrics: Kawasaki, neonatal conjunctivitis

— Corneal abrasion (24–48 h)

— Uncomplicated viral keratoconjunctivitis with persistent symptoms

— Episcleritis (1 week)

— Recurrent uveitis on maintenance therapy

CCS pearl: Endogenous endophthalmitis in an IV drug user should trigger blood cultures × 2, TTE, then TEE if suspicious, ID consult, vitreous tap and inject — Candida and S. aureus are top organisms.

Step 3 management: A patient discharged on topical fluoroquinolone for corneal abrasion in a contact lens wearer must have ophthalmology follow-up arranged within 24 hours before leaving the clinic — document the appointment.

Same-day (within hours) ophthalmology consultation:

Admission criteria:

Multidisciplinary consults:

Outpatient ophthalmology follow-up (within 1–7 days):

Key Differentials — Other Eye Causes of Red Eye

— Viral (adenoviral): bilateral (starts unilateral), watery, preauricular adenopathy, follicular conjunctival reaction, recent URI; epidemic keratoconjunctivitis can leave subepithelial infiltrates and decreased vision for weeks

— Bacterial (S. aureus, S. pneumoniae, H. influenzae): purulent, lids stuck shut on waking, less itch

— Hyperacute (N. gonorrhoeae): profuse purulence, marked lid swelling, chemosis, can perforate cornea

— Chlamydial (adult inclusion): chronic follicular, mucopurulent, often with GU symptoms

— Allergic: bilateral, intense itch, chemosis, cobblestone papillae, atopy history

— Toxic / preservative: chronic eye drop use (BAK preservative)

— Bacterial (Pseudomonas in contact lens), fungal (post-vegetative trauma), HSV (dendrite), Acanthamoeba (pain out of proportion), exposure keratopathy (Bell's palsy, lagophthalmos)

— Anterior most commonly presents as painful red eye

— Acute angle-closure (painful red eye)

— Open-angle (asymptomatic, not in this differential)

— Neovascular (diabetic, post-CRVO)

— Blepharitis (anterior — staph, seborrheic; posterior — meibomian gland dysfunction)

— Hordeolum (acute, painful — staph abscess of gland of Zeis or meibomian)

— Chalazion (chronic, painless granuloma — not usually red/painful)

— Dacryocystitis (medial canthal swelling, pain, expressible pus)

— Dacryoadenitis (lateral upper lid swelling — S-shaped lid)

— Dry eye / keratoconjunctivitis sicca (Sjögren)

— Pterygium, pinguecula

— Subconjunctival hemorrhage (painless and bright red — typically not painful unless traumatic)

Key distinction: Preauricular lymphadenopathy with red eye = adenoviral conjunctivitis or gonococcal/chlamydial conjunctivitis, not routine bacterial — a quick palpation reorders your differential.

Board pearl: Cobblestone papillae on tarsal conjunctiva = vernal keratoconjunctivitis (boys, spring, atopy) — treat with topical mast cell stabilizers/steroids under ophthalmology.

Conjunctivitis subtypes (the most common bucket):

Keratitis:

Uveitis (anterior, intermediate, posterior, panuveitis):

Glaucoma:

Scleritis / episcleritis

Endophthalmitis

Lid and adnexal disease:

Surface disease:

Key Differentials — Systemic and Non-Ocular Mimics

— Seronegative spondyloarthropathies (ankylosing spondylitis, reactive arthritis, IBD-associated, psoriatic): recurrent unilateral HLA-B27 anterior uveitis

— Sarcoidosis: granulomatous uveitis ("mutton-fat" keratic precipitates), lacrimal gland enlargement, Heerfordt syndrome (uveitis + parotitis + facial palsy + fever)

— Behçet disease: hypopyon uveitis with retinal vasculitis, oral and genital ulcers

— Granulomatosis with polyangiitis (GPA): scleritis, peripheral ulcerative keratitis, orbital pseudotumor, nasal involvement; c-ANCA/PR3

— Rheumatoid arthritis: scleritis (necrotizing, painful), keratoconjunctivitis sicca, peripheral ulcerative keratitis ("corneal melt")

— Syphilis / TB: any pattern of uveitis or scleritis — "great mimickers"

— Lyme disease: conjunctivitis, uveitis, keratitis in endemic regions

— HIV: HZO, CMV retinitis, microvasculopathy

— Kawasaki disease: bilateral nonexudative conjunctivitis in febrile child

— Stevens-Johnson syndrome / TEN: mucosal involvement → pseudomembranous conjunctivitis, symblepharon

— Thyroid eye disease: chemosis, injection, proptosis, lid retraction, restrictive ophthalmopathy

— Carotid-cavernous fistula: pulsatile proptosis, dilated "corkscrew" episcleral vessels, bruit, elevated IOP

— Migraine, cluster headache (V1 distribution, autonomic — tearing, miosis, ptosis, conjunctival injection)

— Trigeminal neuralgia

— Sinusitis with referred orbital pain

— Dental abscess

— Temporal arteritis (GCA)

— Subarachnoid hemorrhage with subhyaloid hemorrhage and meningismus

— Carbon monoxide exposure (bilateral conjunctival injection in mass exposures)

Key distinction: Cluster headache = severe unilateral periorbital pain with ipsilateral lacrimation, conjunctival injection, ptosis, miosis, and nasal congestion lasting 15–180 minutes — abortive with high-flow oxygen and sumatriptan SC; not an ophthalmologic emergency but often misdiagnosed.

Board pearl: A recurrent unilateral anterior uveitis in a young man with low back stiffness → check HLA-B27 and sacroiliac films/MRI for ankylosing spondylitis.

Systemic conditions presenting as red eye:

Non-ocular mimics:

Secondary Prevention and Long-Term Management

— No sleeping in lenses (extended-wear lenses still carry 5× risk)

— No tap water for cleaning or storage; no showering or swimming with lenses

— Rub and rinse with multipurpose solution; replace case every 3 months

— Daily disposable lenses lower infection risk

— Discontinue lenses immediately if pain or redness; do not "wait it out"

Step 3 management: A patient discharged after laser iridotomy for AACG should be scheduled for: ophthalmology follow-up at 1 week, prophylactic LPI on the fellow eye within 1–2 weeks, medication reconciliation to remove anticholinergic offenders, and counseling about future medication interactions (e.g., topiramate, sulfas).

Board pearl: HEDS trial: long-term oral acyclovir reduces HSV keratitis recurrence by ~50% in patients with prior stromal disease.

Contact lens wearers — counseling to prevent keratitis recurrence:

Recurrent HSV keratitis: long-term oral acyclovir 400 mg BID (HEDS trial — reduces recurrence ~50%)

HZO: Shingrix vaccine for adults ≥50 (and immunocompromised ≥19); does not eliminate but reduces incidence and post-herpetic neuralgia

AACG: prophylactic laser peripheral iridotomy on fellow eye; counsel about anticholinergic and sympathomimetic drug avoidance; medical-alert ID

Allergic conjunctivitis: identify and avoid triggers, allergen-impermeable bedding, daily disposable lenses, year-round olopatadine for chronic atopics

Dry eye / blepharitis: lid hygiene with warm compresses and dilute baby shampoo or commercial lid scrubs, omega-3 supplementation, artificial tears (preservative-free if used >4×/day), cyclosporine 0.05% or lifitegrast for moderate-severe disease

Uveitis maintenance: steroid taper, immunomodulators (methotrexate, mycophenolate, adalimumab — FDA-approved for non-infectious uveitis); screen and treat underlying systemic disease

Scleritis: NSAIDs for episcleritis and mild scleritis; systemic steroids and DMARDs for moderate-severe; treat underlying vasculitis

Glaucoma after uveitis or trauma: chronic IOP-lowering drops, monitor disc and visual fields

Post-orbital-cellulitis: complete 10–14 day antibiotic course, ENT follow-up for chronic sinus disease, dental evaluation if odontogenic source

Follow-Up, Monitoring, and Counseling

— Viral conjunctivitis: as needed; return if vision changes or symptoms >2 weeks

— Bacterial conjunctivitis: 48–72 h if no improvement

— Corneal abrasion (non-CL): 24–48 h

— Corneal abrasion (CL wearer) / bacterial keratitis: daily with ophthalmology until improving

— Anterior uveitis: ophthalmology q1–7 days during flare; q3–6 months when quiet

— AACG post-LPI: 1 day, 1 week, 1 month, then routine glaucoma surveillance

— HZO: ophthalmology within 1 week; monitor for delayed stromal/uveitic disease for months

— Orbital cellulitis: daily inpatient until afebrile and improving, then outpatient at 1 and 4 weeks; ENT for sinus follow-up

— Visual acuity at every visit

— IOP for uveitis on steroids (steroid-responder risk), post-AACG, post-trauma

— Slit-lamp for anterior chamber cell, corneal epithelial integrity

— Fundoscopy for posterior involvement

— Systemic: ESR/CRP, CBC, LFTs, renal function if on systemic immunomodulators

— Viral conjunctivitis is contagious 10–14 days — stay home from work/school until tearing stops; wash hands; separate towels and pillowcases

— Do not share eye makeup or contact lens supplies; replace makeup after any conjunctivitis

— Avoid topical decongestants (naphazoline) chronically — rebound redness

— Sunglasses with UV protection reduce pterygium recurrence and dry eye

— Quit smoking — accelerates dry eye, thyroid eye disease, AMD

— Sleep hygiene and screen breaks (20-20-20 rule) for computer vision syndrome

— Worsening pain, decreased vision, photophobia, halos, or persistent symptoms >7 days → return or go to ED

CCS pearl: When advancing the clock on a patient with conjunctivitis or corneal abrasion, always re-check visual acuity and re-examine with fluorescein at follow-up — these are the parameters graders look for.

Board pearl: Steroid-responders develop ocular hypertension on topical steroids; monitor IOP at every visit when steroids are used >2 weeks.

Follow-up cadence by diagnosis:

Monitoring parameters:

Counseling pearls:

Return-precaution counseling for any red eye discharged from primary care:

Ethical, Legal, and Patient Safety Considerations

— Gonococcal and chlamydial conjunctivitis are reportable STIs in all US states; report cases, ensure partner notification and treatment (expedited partner therapy where legally permitted)

— Neonatal gonococcal ophthalmia triggers an investigation into prenatal care; report per state law

— Suspected child abuse with ocular trauma (especially retinal hemorrhages in infants — shaken baby) is a mandatory report; document findings, preserve evidence, involve child protective services, do not confront caregiver in confrontational manner

— Suspected intimate partner violence with ocular injury — screen privately, document, offer resources; reporting laws vary by state

— Refusal of neonatal erythromycin prophylaxis: document parental refusal, counsel on gonococcal ophthalmia risk; in most states it is statutorily required and refusal must be documented

— AACG patient with altered mental status from pain/nausea: implied consent for emergent IOP-lowering treatment; document

— Jehovah's Witness with hyphema: blood products rarely needed but discuss preferences before any surgical intervention

— Failure to arrange same-day ophthalmology follow-up for contact-lens-associated abrasion → Pseudomonas keratitis lawsuit pattern

— Missed AACG in ED triaged as "headache with nausea" — every headache with eye symptoms needs visual acuity and pupil exam

— HSV keratitis treated with topical steroids without antiviral coverage → corneal perforation

— Discharge without contact information for ophthalmology

— Patients with cycloplegic dilation or monocular patching should not drive home; arrange transportation

— Counsel on visual field requirements for driver's license — vary by state

— Eye protection mandates (OSHA) — counsel grinding/welding workers; document

— Return-to-work notes after infectious conjunctivitis (food handlers, healthcare workers — out until discharge resolves)

Step 3 management: A healthcare worker with viral conjunctivitis must be furloughed from direct patient care until ocular discharge resolves (typically 10–14 days) — written work restriction is part of the visit.

Board pearl: Bilateral retinal hemorrhages in an infant with altered mental status = abusive head trauma until proven otherwise — report, get neuroimaging, admit.

Mandatory reporting and public health:

Informed consent edge cases:

Transition-of-care risks (Step 3 favorite):

Driving safety:

Workplace safety:

High-Yield Associations and Rapid-Fire Facts

— Halos around lights + nausea + mid-dilated pupil → AACG

— Contact lens + pain + white infiltrate → bacterial keratitis (Pseudomonas)

— Contact lens + pain out of proportion + ring infiltrate + swimming → Acanthamoeba

— Dendritic ulcer on fluorescein → HSV keratitis (no steroids!)

— Hutchinson sign (tip-of-nose vesicle) → HZO (V1 nasociliary branch)

— Hypopyon → endophthalmitis, severe keratitis, or Behçet uveitis

— Mutton-fat keratic precipitates → granulomatous uveitis (sarcoid, TB, syphilis)

— "Can't see, can't pee, can't climb a tree" → reactive arthritis (uveitis/conjunctivitis + urethritis + arthritis)

— Pulsatile proptosis + bruit + corkscrew vessels → carotid-cavernous fistula

— Bilateral painless conjunctival injection + fever ≥5 days in child → Kawasaki

— S-shaped upper lid → dacryoadenitis

— Medial canthal pus + pain → dacryocystitis

— Boring pain waking patient + bluish hue → scleritis (RA, GPA)

— Painless bright red blood under conjunctiva → subconjunctival hemorrhage (check BP, anticoagulants, Valsalva)

— Day 2–5 newborn purulent conjunctivitis → gonococcal (IM ceftriaxone, admit)

— Day 5–14 newborn mucopurulent → chlamydial (oral erythromycin)

— Topiramate, sulfa drugs → bilateral angle closure (ciliary body swelling)

— Anticholinergics, decongestants → angle closure in predisposed eyes

— Topical steroids → IOP rise, HSV reactivation, fungal keratitis

— Amiodarone → corneal verticillata (vortex keratopathy)

— Hydroxychloroquine → retinopathy (annual OCT/visual field after 5 years or earlier in risk)

— EVS: pars plana vitrectomy for endophthalmitis only when vision = light perception

— HEDS: long-term oral acyclovir reduces HSV keratitis recurrence

— CHAMPS/ONTT: optic neuritis (not in this differential but commonly confused) — IV methylprednisolone speeds recovery

Board pearl: Phenylephrine blanch test: episcleritis blanches (superficial vessels), scleritis does not (deep vessels) — distinguishes the two at the bedside.

Pattern → diagnosis:

Drug-induced ocular emergencies:

Trial pearls:

Board Question Stem Patterns

— Answer: Acute angle-closure glaucoma — topical timolol/brimonidine/pilocarpine, IV acetazolamide, urgent ophthalmology for laser peripheral iridotomy; LPI to fellow eye prophylactically.

— Answer: Pseudomonas keratitis — stop lenses, topical moxifloxacin hourly, same-day ophthalmology for cultures; never patch.

— Answer: HLA-B27 anterior uveitis / ankylosing spondylitis — topical prednisolone + cycloplegic, refer to rheumatology, SI joint imaging.

— Answer: Giant cell arteritis — start high-dose IV methylprednisolone immediately, temporal artery biopsy within 1–2 weeks.

— Answer: Gonococcal ophthalmia neonatorum — admit, IM/IV ceftriaxone single dose, saline lavage, evaluate for disseminated disease, report and treat mother.

— Answer: Orbital cellulitis with subperiosteal abscess — admit, IV vancomycin + ceftriaxone, ENT consult; if no improvement at 48 h or large abscess, surgical drainage.

— Answer: HZO with high ocular risk (Hutchinson sign) — oral valacyclovir 1 g TID × 7 days, ophthalmology evaluation; counsel on Shingrix (after acute episode).

— Answer: Post-op endophthalmitis — emergent vitreous tap with intravitreal vancomycin + ceftazidime; vitrectomy if light perception only.

Step 3 management: When the stem gives "contact lens + pain + infiltrate," the answer is topical fluoroquinolone + immediate ophthalmology — never the topical steroid or eye patch.

Stem 1: A 62-year-old hyperopic woman develops severe right eye pain, headache, nausea, and sees halos around lights after watching a movie in a dark theater. Exam: cloudy cornea, mid-dilated nonreactive pupil, rock-hard globe, IOP 52.

Stem 2: A 22-year-old soft contact lens wearer who swims in lenses has 3 days of severe right eye pain, photophobia, and a 2 mm white corneal infiltrate with overlying fluorescein uptake.

Stem 3: A 35-year-old man with low back pain that improves with exercise has his third episode of unilateral painful red eye with ciliary flush, photophobia, and AC cell.

Stem 4: A 70-year-old woman with new headache, jaw pain on chewing, transient vision loss, ESR 95.

Stem 5: A 4-day-old infant born vaginally to a mother with poor prenatal care has copious purulent bilateral discharge and lid swelling.

Stem 6: A diabetic with painful proptotic eye, fever, restricted upward gaze, and ethmoid sinus opacification on CT.

Stem 7: A 50-year-old with V1 dermatomal vesicles including the tip of the nose, eye pain, and conjunctival injection.

Stem 8: Recent cataract surgery patient returns at day 4 with pain, decreased vision, and hypopyon.

One-Line Recap

The painful red eye is a triage problem first and a treatment problem second: identify decreased vision, deep pain, photophobia, ciliary flush, fixed pupil, halos, or contact lens use — any of which converts a routine "pink eye" into a vision-threatening emergency that demands same-day ophthalmology evaluation rather than a topical antibiotic.

Board pearl: The single highest-yield rule for Step 3: any red eye with decreased visual acuity or photophobia is sight-threatening until ophthalmology proves otherwise — don't prescribe drops and discharge; document the same-day referral and the return precautions before the patient leaves the clinic.

Tier 1 emergencies (refer in minutes to hours): acute angle-closure glaucoma, bacterial/Acanthamoeba/fungal keratitis, endophthalmitis, orbital cellulitis, chemical burn (irrigate first), globe rupture, hyperacute (gonococcal) conjunctivitis, HZO with Hutchinson sign, suspected GCA.

Tier 2 urgent (same- or next-day ophthalmology): anterior uveitis, scleritis, hyphema, HSV keratitis (dendrite), contact-lens-associated abrasion.

Tier 3 primary care (treat and counsel): viral conjunctivitis (supportive, hygiene, contagious 10–14 days), bacterial conjunctivitis (topical antibiotic), allergic conjunctivitis (olopatadine, avoid rubbing), simple non-CL corneal abrasion (topical antibiotic, no patching, no home anesthetics), dry eye/blepharitis (warm compresses, artificial tears), subconjunctival hemorrhage (reassure, check BP/anticoagulation).

Universal four-step office workup: visual acuity, pupil exam, fluorescein staining, intraocular pressure — these four orders capture nearly every diagnosis on the differential and are the standard CCS opening for any painful red eye encounter.