Painless red eye

A painless red eye is redness of the eye with little or no pain and no major loss of vision. Most cases are conjunctivitis or subconjunctival haemorrhage and need only simple treatment.

Anatomy. The conjunctiva covers the sclera and the inner eyelids. Conjunctival injection is diffuse and greatest in the fornices. Ciliary (limbal) flush is a ring of deep injection around the limbus and indicates keratitis, uveitis or angle closure. Episcleral vessels lie deeper and blanch with phenylephrine 2.5 percent drops; scleral vessels do not.

Classification. Conjunctival (infective, allergic, irritant, toxic), episcleral and scleral, subconjunctival haemorrhage, and lid and lacrimal causes. Acute (under 4 weeks) or chronic.

Key distinctions. Itch indicates allergy. Discharge indicates infection (watery in viral, purulent in bacterial). Red eye with reduced vision, photophobia, pain or a fixed pupil is not a simple conjunctivitis.

History.

• Onset, laterality, discharge (watery, mucopurulent, ropy), itch, grittiness, pain, photophobia, vision change.
• Contact lens use, recent trauma, foreign body, chemical exposure, sick contacts, recent cold.
• Sexual history (gonorrhoea, chlamydia), atopy, hay fever, eczema, contact with cats (Bartonella), previous episodes.
• Autoimmune disease (rheumatoid arthritis, ankylosing spondylitis), and use of topical drugs.

Drug history. Topical drops (preservatives, aminoglycosides, antivirals), anticoagulants and antiplatelets (subconjunctival haemorrhage), isotretinoin, and systemic drugs causing red eye.

Examination.

• Visual acuity with correction or pinhole in each eye (always), pupils (size, shape, reaction).
• Eyelids (swelling, ectropion, entropion, trichiasis, blepharitis, lumps).
• Conjunctiva (follicles, papillae, membrane, haemorrhage, chemosis).
• Cornea (clarity, fluorescein staining with a cobalt blue light or slit lamp), anterior chamber (cells, hypopyon).
• Intraocular pressure when angle closure is suspected, preauricular lymph node, and eversion of the upper lid for foreign body.

Red flags

• Reduced visual acuity not improving with blinking
• Photophobia, pain, ciliary flush, corneal opacity or staining, hypopyon, or irregular pupil
• Contact lens wearer with redness (corneal ulcer)
• Chemical injury, penetrating injury or high speed foreign body
• Newborn with discharge in the first 28 days (ophthalmia neonatorum)
• Neonate or immunosuppressed adult with purulent conjunctivitis and membrane
• Vesicular rash on the forehead or tip of nose (herpes zoster ophthalmicus)
• Severe purulent discharge with rapid onset (gonococcal)
• Proptosis or restricted eye movements

Special groups. Children: viral and bacterial conjunctivitis, allergic conjunctivitis; neonates need urgent assessment. Pregnancy: avoid tetracyclines and fluoroquinolones systemically; topical chloramphenicol only with caution. Region specific: trachoma, vernal keratoconjunctivitis, and onchocerciasis occur in some regions.

Conjunctival

• Viral conjunctivitis (adenovirus), epidemic keratoconjunctivitis, pharyngoconjunctival fever, herpes simplex, varicella zoster, enterovirus (acute haemorrhagic)
• Bacterial conjunctivitis (Staphylococcus, Streptococcus, Haemophilus, Moraxella)
• Gonococcal conjunctivitis, chlamydial inclusion conjunctivitis, trachoma
• Ophthalmia neonatorum (chemical, gonococcal, chlamydial, herpetic)
• Allergic conjunctivitis (seasonal, perennial), vernal and atopic keratoconjunctivitis, giant papillary conjunctivitis
• Toxic and irritant conjunctivitis (drop preservatives), dry eye
• Parinaud oculoglandular syndrome (cat scratch, tularaemia, tuberculosis)

Haemorrhagic and vascular

• Subconjunctival haemorrhage (Valsalva, trauma, coughing, hypertension, anticoagulants, bleeding disorders)
• Conjunctival chemosis, carotid cavernous fistula (arterialised vessels, bruit), and caroticocavernous fistula

Episcleral and scleral

• Episcleritis (simple and nodular), scleritis (anterior, posterior, necrotising)

Lid and lacrimal

• Blepharitis, chalazion, stye, entropion, ectropion, trichiasis, dacryocystitis, canaliculitis

Sight threatening conditions that may be painless early

• Uveitis, keratitis, corneal ulcer, acute angle closure glaucoma, endophthalmitis

Other

• Pterygium and pinguecula, conjunctival tumours (including Kaposi sarcoma and ocular surface squamous neoplasia), foreign body, contact lens overwear
• Systemic: Kawasaki disease, leptospirosis, measles, Stevens Johnson syndrome

Reasoning. Check vision and look for signs of deeper disease. Treat clear cases of mild conjunctivitis, and refer urgently where red flags are present.

First line. Visual acuity, pupils, fluorescein staining and slit lamp or penlight examination, lid eversion, and intraocular pressure when angle closure is possible.

Targeted tests.

• Conjunctival swab for culture and sensitivity in neonates, severe purulent discharge, contact lens wearers, treatment failure, and suspected gonococcal infection. Nucleic acid amplification test for chlamydia and gonorrhoea. Viral PCR or antigen test for herpes simplex and adenovirus when diagnosis is unclear.
• Conjunctival scrape for Giemsa stain and cytology (eosinophils in allergy, inclusion bodies in chlamydia).
• Phenylephrine 2.5 percent test to separate episcleritis from scleritis.
• Blood pressure, glucose, full blood count and clotting profile for recurrent subconjunctival haemorrhage.
• Autoimmune and infective screen for scleritis (ESR, C reactive protein, rheumatoid factor, ANCA, antinuclear antibody, syphilis serology, interferon gamma release assay, chest radiograph).
• B scan ultrasound or MRI for posterior scleritis or suspected mass.

Limitations. Clinical distinction of viral from bacterial conjunctivitis is imperfect. Swabs are often negative.

Urgent conditions (same day ophthalmology):

• reduced vision
• corneal involvement
• contact lens related redness
• chemical injury (irrigate with at least 1 to 2 L of saline or water until pH is 7.0 to 7.4 before transfer)
• penetrating injury (shield, no pressure, no topical drops)
• neonatal conjunctivitis
• suspected herpes zoster ophthalmicus, scleritis, uveitis and suspected angle closure

Viral conjunctivitis. Self limiting over 1 to 3 weeks. Cold compresses, lubricant drops (hypromellose 0.3 percent or carbomer gel, 1 drop up to every 1 to 2 hours), and hygiene to reduce spread (hand washing, no towel sharing, school or work exclusion until discharge settles). No antibiotics. Avoid topical corticosteroids without ophthalmology review. Epidemic keratoconjunctivitis with corneal infiltrates: ophthalmology care.

Bacterial conjunctivitis. Often self limiting within 5 to 7 days.

Chloramphenicol 0.5 percent eye drops, 1 drop every 2 hours for the first 48 hours (while awake), then 4 times daily for 5 days in total.

Alternatives: fusidic acid 1 percent gel 1 drop twice daily for 7 days, ofloxacin 0.3 percent 1 drop four times daily for 5 days, or azithromycin 1.5 percent 1 drop twice daily for 3 days.

Treat contact lens wearers with an antipseudomonal fluoroquinolone (ofloxacin 0.3 percent or ciprofloxacin 0.3 percent, 1 drop every 1 to 2 hours initially) and refer the same day. Stop lens wear.

Gonococcal and chlamydial conjunctivitis.

• Gonococcal: ceftriaxone 1 g IM as a single dose (1 g IV daily for 3 days when keratitis), with saline irrigation of the eye and partner treatment.
• Add doxycycline 100 mg orally twice daily for 7 days when chlamydia is not excluded.
• Urgent ophthalmology review for corneal involvement.

Chlamydial inclusion conjunctivitis: azithromycin 1 g orally as a single dose or doxycycline 100 mg orally twice daily for 7 days, with partner treatment. Trachoma: azithromycin 20 mg/kg orally as a single dose (maximum 1 g) with face washing and environmental measures; surgery for trichiasis.

Ophthalmia neonatorum. Same day paediatric and ophthalmology care:

• ceftriaxone 25 to 50 mg/kg IV or IM as a single dose (maximum 125 mg) for gonococcal infection
• azithromycin 20 mg/kg orally daily for 3 days for chlamydia
• aciclovir 20 mg/kg IV every 8 hours for suspected herpes simplex
• saline irrigation; screening and treatment of the mother and partner

Allergic conjunctivitis. Avoid allergen and rubbing, cold compresses, lubricants, and topical antihistamine mast cell stabiliser:

• olopatadine 0.1 percent 1 drop twice daily
• or ketotifen 0.025 percent 1 drop twice daily (age 3 years and older)
• or sodium cromoglicate 2 percent 1 to 2 drops four times daily (slow onset)

Oral loratadine 10 mg once daily for associated rhinitis. Vernal keratoconjunctivitis and severe atopic disease: ophthalmology care with topical ciclosporin 0.05 to 0.1 percent and short courses of steroids under supervision.

Subconjunctival haemorrhage. Reassurance, lubricants, and resolution within 2 to 3 weeks; check blood pressure and anticoagulant levels (INR) when recurrent or on warfarin; no treatment needed.

Episcleritis. Cold compresses and lubricants; oral NSAID (ibuprofen 400 mg orally three times daily with food for 5 to 7 days; avoid in renal impairment, heart failure and peptic ulcer) or topical fluorometholone 0.1 percent under ophthalmology care; recurrent episodes need screening for systemic disease.

Scleritis. Urgent ophthalmology and rheumatology: oral NSAID or prednisolone 1 mg/kg daily (maximum 60 to 80 mg) with immunosuppression for necrotising or posterior disease.

Blepharitis. Lid hygiene (warm compress for 5 to 10 minutes then lid scrubs twice daily), and doxycycline 100 mg orally daily for 6 to 12 weeks for meibomian gland disease (avoid in pregnancy and in children under 12 years).

Dacryocystitis. Warm compresses, amoxicillin with clavulanic acid 625 mg orally three times daily for 7 days, and ENT or ophthalmology referral for drainage or dacryocystorhinostomy.

Herpes simplex and zoster. Ophthalmology care.

• Dendritic keratitis: aciclovir 3 percent ointment 5 times daily or ganciclovir 0.15 percent gel 5 times daily until the ulcer heals.
• Herpes zoster ophthalmicus: valaciclovir 1 g orally three times daily for 7 days (adjusted for kidney function: creatinine clearance 30 to 49 mL/min, 1 g every 12 hours; 15 to 29 mL/min, 1 g daily; under 15 mL/min, 500 mg daily), with same day ophthalmology review.

Monitoring. Review at 48 to 72 hours for deteriorating or non-improving infective cases, at 1 week for allergy, and at 2 weeks for persistent redness. Check visual acuity at each review.

Referral and escalation. Same day ophthalmology for red flags. Routine ophthalmology for persistent redness beyond 2 weeks, recurrent episodes, or chronic conditions. Public health for outbreaks and notifiable infections.

Admission criteria. Orbital cellulitis, endophthalmitis, neonatal gonococcal or herpetic infection, severe chemical injury, or necrotising scleritis.

Discharge and safety netting. Advise on hygiene and no lens wear. Return for pain, photophobia, reduced vision, increasing discharge, swelling of the lids, or no improvement in 48 to 72 hours.