Assessment and examination

Approach to red eye

Overview and approach

Red eye ranges from benign surface disease to sight-threatening inflammation, infection or glaucoma.

  • Conjunctivitis accounts for over 25% of eye complaints in Australian general practice, and can be allergic, viral or bacterial (1). Serious causes are less common but must be recognised: keratitis, scleritis, uveitis, endophthalmitis, acute angle closure and penetrating injury (2).
  • A simple way to sort the red eye: extra-ocular (orbital cellulitis), external (lids, conjunctiva, sclera, cornea) and internal (anterior chamber, iris, ciliary body: uveitis, angle closure) (3).
Assessment and clinical features

Check acuity, pain, photophobia, discharge, pupil, corneal clarity, contact lenses and recent surgery/trauma.

  • Ask: time course, pain, vision, trauma, photophobia, foreign body sensation, itch, discharge, contact lens wear, fever, previous eye surgery (1)(2). Also ask about cold sores, autoimmune disease and anticoagulants (2).
  • Features of an internal cause (3): severe pain unrelieved by topical anaesthetic, impaired vision, poorly reactive pupil, abnormal slit-lamp findings or pressure. Surface disease gives gritty/itchy/burning pain that is much improved by topical anaesthetic, with near-normal acuity.
  • Discharge pattern: purulent = bacterial; watery with pre-auricular node = viral; itch with bilateral signs and atopy = allergic (1).
Differentials and investigations

Consider conjunctivitis, episcleritis, scleritis, uveitis, keratitis and angle closure; examine with fluorescein/slit lamp when appropriate.

  • Pain, photophobia, watery: foreign body, corneal abrasion/ulcer, herpetic ulcer, acute angle closure (2). Purulent: bacterial conjunctivitis, infectious keratitis, endophthalmitis (2). Dull aching pain: iritis, scleritis (2). Painless sectoral/patchy redness: subconjunctival haemorrhage, episcleritis (2).
  • Acute angle closure: severe pain and headache, nausea/vomiting, halos, cloudy cornea, fixed mid-dilated pupil (1)(3). Significant pain leading to vomiting, circumciliary injection (unilateral), reduced acuity, photophobia, haloes, hazy cornea, mid-dilated unreactive pupil. Risk factors: female, increasing age, East Asian ethnicity, drugs, family history, hyperopia, shallow anterior chamber. Management: acetazolamide.
  • Painful red eye (reduced VA, photophobia): scleritis, uveitis, corneal abrasion and corneal ulcer (see Uveitis, scleritis and microbial keratitis), acute angle-closure glaucoma, and foreign bodies.
  • Foreign body: may be visible on the surface or embedded in cornea or sclera; redness, pain, watering and foreign body sensation; may hide under the upper or lower lid. Corneal FB is also listed among painless-looking causes.
  • Painless red eye: conjunctivitis (diffuse injection, discharge, chemosis; bacterial more purulent; allergic itchy; no visual defect); subconjunctival haemorrhage (flat, bright red patch with sharp borders and normal conjunctiva around it); episcleritis (sectoral superficial injection that moves with a swab pressed gently on the conjunctiva under topical anaesthesia); dry eye (see Conjunctivitis, dry eye and blepharitis).
  • Herpes simplex keratitis: branching dendritic ulcer staining with fluorescein; viral swab for HSV PCR (1).
  • Examination: acuity with pinhole, pupils (RAPD), fluorescein with cobalt blue light, lid eversion, pre-auricular nodes (1). See Ophthalmic history and examination.
Management and follow-up

Arrange urgent eye review for reduced vision, marked pain, corneal opacity or a concerning pupil. Treat uncomplicated surface disease according to cause.

  • Bacterial conjunctivitis (RCH, children): eye toilet and chloramphenicol 0.5% drops 4-6 times a day for 5-7 days; stop and seek ophthalmology advice if hypersensitivity (2).
  • Viral conjunctivitis: self-limiting over 1-3 weeks; lubricants, cool compresses and hygiene; contagious while the eye is tearing (2). Suspect HSV if lid vesicles, reduced vision or photophobia and swab for PCR (2).
  • Allergic: antihistamine (oral or topical) and artificial tears (2).
  • Dendritic ulcer (HSV keratitis): topical aciclovir ointment five times daily with prompt specialist referral (1).
  • Subconjunctival haemorrhage: observe; resolves in 1-3 weeks. If recurrent, look for a bleeding disorder (2).
  • Urgent ophthalmology: infectious keratitis (keep the contact lens for culture), endophthalmitis, acute angle closure, scleritis/uveitis, corneal opacity (2)(3).
Red flags and clinical pearls

Do not assume conjunctivitis when visual acuity is reduced. Avoid empiric topical steroids without ophthalmology advice.

  • Prompt specialist referral (RACGP): contact lens wearer, previous eye/refractive surgery, decreased vision, severe pain, nausea and vomiting, cloudy or opaque cornea, dendritic ulcer, hypopyon, non-reactive pupil or RAPD, trauma, persisting or worsening symptoms (1).
  • A contact lens wearer with a painful red eye needs prompt specialist assessment: Pseudomonas and Acanthamoeba keratitis can perforate the cornea (1).
  • Topical steroids can be disastrous in herpes keratitis; an initial steroid prescription should come from an ophthalmologist after full examination (1). A patient who fails to respond to chloramphenicol needs re-examination, not a second antibiotic (1).
  • Subconjunctival haemorrhage after trauma may mean open globe; in infants it can be a sign of non-accidental injury (2).
References
  1. Sharma, Ooi, Li. A painful red eye. Aust Fam Physician 2009 (RACGP)
  2. RCH Clinical Practice Guidelines: Acute red eye
  3. Collins N. Acute angle closure for emergency physicians (RVEEH, Eye and Ear)

Last updated from Sen’s notes on 9 October 2026.