Eyes & Vision

Conjunctivitis

A superficial red, gritty, itchy or discharging eye caused by infection, allergy or irritation; preserved vision and a comfortable cornea support the diagnosis, while pain, photophobia, reduced vision, contact-lens use or neonatal disease needs urgent escalation.

In a nutshell

Conjunctivitis is a superficial red eye with discharge or itch, preserved vision and no significant pain. First exclude keratitis, uveitis, glaucoma, neonatal infection and contact-lens disease; then use hygiene and cause-specific treatment rather than universal antibiotics.

Classic presentation

A comfortable red, gritty or itchy eye with watery or sticky discharge, preserved vision and a normal pupil; viral and allergic disease are often bilateral.

Key points

Pain, photophobia, reduced vision, corneal involvement or a contact-lens red eye is not routine conjunctivitis until urgent eye assessment excludes keratitis or another sight-threatening cause.
Viral disease is usually watery and self-limiting; bacterial disease may be sticky or purulent; allergic disease is dominated by itch and is not contagious.
Clean the lids, wash hands, avoid sharing towels or drops and avoid contact lenses until the eyes are better.
Topical antibiotics do not treat viral or allergic disease and should not delay urgent contact-lens or neonatal assessment.
A baby under 30 days with a red sticky eye needs urgent assessment for ophthalmia neonatorum.
Do not routinely exclude people from school or work unless they are very unwell; follow local policy where the setting involves vulnerable people.
Reassess if symptoms have not cleared within 7 days or if pain, photophobia, visual change or corneal symptoms develop.

First-line investigation

Visual acuity, pupil and corneal assessment; fluorescein when pain, photophobia or corneal involvement is possible. Routine swabs are not needed.

Management

Exclude sight-threatening red-eye causes

Urgently assess pain, photophobia, reduced or distorted vision, corneal opacity or staining, marked circumcorneal redness, proptosis, restricted eye movements and severe unilateral redness. Treat a red contact-lens eye as possible microbial keratitis until assessed.^1,3,4
A neonate or baby under 30 days with a red sticky eye needs urgent assessment for ophthalmia neonatorum and possible gonococcal or chlamydial infection.^3,1

Confirm the superficial pattern

Document visual acuity, pupil reaction, pattern of redness, pain, discharge, corneal appearance and contact-lens use. Simple conjunctivitis should have essentially preserved vision and no marked pain or photophobia.^1,2,3
Use fluorescein and slit-lamp or urgent eye assessment when corneal involvement is possible; do not use routine swabs to replace a red-eye examination.^1,4

Support recovery and limit spread

Clean crusts with clean water, use a cool compress, wash hands, avoid rubbing and do not share towels, pillows or eye drops. Stop contact lenses until the eyes are completely better. Routine school or work exclusion is not required unless the person is very unwell.^3,4
For uncomplicated viral conjunctivitis, use supportive care and explain that antibiotics will not help. For suitable bacterial disease, consider topical chloramphenicol using current BNF advice; do not let treatment delay contact-lens or neonatal referral.^1,5

Treat allergy and avoid unsafe drops

For allergic conjunctivitis, reduce trigger exposure, use cool compresses and consider ketotifen or sodium cromoglicate according to age, pregnancy and BNF cautions. Avoid rubbing the eyes and do not start steroid eye drops in an undifferentiated red eye without specialist direction.^2,6,7

Protect contact-lens wearers and neonates

Remove contact lenses and arrange urgent eye assessment for a red or painful lens wearer, especially with photophobia, reduced vision or a corneal spot; routine chloramphenicol alone is not an adequate substitute for excluding microbial keratitis.^1,4,5
Arrange urgent specialist, microbiology and sexual-health pathways for suspected neonatal, gonococcal or chlamydial conjunctivitis because corneal damage can occur and topical treatment alone may be inadequate.^1,3

Review persistence or diagnostic uncertainty

Reassess if symptoms have not cleared within 7 days, worsen, recur or develop pain, photophobia, visual change or corneal symptoms. Reconsider keratitis, uveitis, glaucoma, blepharitis, nasolacrimal disease, chlamydial infection or another inflammatory cause.^3,1,2

Exam traps

A contact-lens wearer with a red or painful eye may have microbial keratitis; do not treat as routine conjunctivitis without urgent assessment.
Discharge colour is suggestive, not diagnostic; the safety examination and preserved vision matter more.
Neonatal conjunctivitis is not routine childhood conjunctivitis: urgent assessment is needed and topical treatment alone may be inadequate.
Pain or photophobia should make you reconsider the diagnosis, even if discharge is present.
Steroid eye drops can worsen undiagnosed corneal infection and should not be started casually in a red eye.

Illustrations

Superficial conjunctival versus deep ciliary injectionComparative diagram showing diffuse superficial conjunctival redness versus circumcorneal ciliary injection seen in sight-threatening disease.PassFinals · original

Purulent bacterial conjunctivitisClinical photograph of a red eye with thick purulent discharge and crusted lashes; discharge supports but does not by itself prove the bacterial cause.Rasbak, Wikimedia Commons · Public domain

Allergic conjunctivitis with chemosisClinical photograph showing bilateral watery, itchy eyes with conjunctival swelling or chemosis.James Heilman, MD, Wikimedia Commons · CC-BY-SA-4.0

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.