Red eye — differential diagnosis (optometry)
Structured for Australian optometry practice.
Clinical decision support only
OptoGuide™ supports professional judgement and does not diagnose or replace clinician responsibility.
Quick answer
- Separate painful red eye from mild irritation early; pain, photophobia, or reduced vision change urgency.
- Common causes include conjunctivitis, dry eye, blepharitis, episcleritis, keratitis, anterior uveitis, and angle-closure glaucoma.
- Check visual acuity, corneal staining, pupil responses, anterior chamber reaction, IOP where appropriate, and contact lens history.
- Refer urgently if there is corneal involvement, severe pain, photophobia, reduced vision, unilateral marked redness, or trauma.
Common causes
- Conjunctivitis: diffuse injection with discharge or itch.
- Dry eye / blepharitis: irritation, fluctuating symptoms, lid margin disease.
- Episcleritis: sectoral redness with mild discomfort.
- Keratitis: pain, photophobia, staining defect, contact lens association.
- Anterior uveitis: ciliary flush, photophobia, cells and flare.
Red flags (must not miss)
- Moderate to severe pain, photophobia, or reduced vision.
- Contact lens wearer with focal staining or infiltrate.
- Corneal opacity, dendritic pattern, or epithelial defect.
- Fixed mid-dilated pupil, nausea, or markedly raised IOP.
- Chemical injury, penetrating trauma, or hypopyon.
Use OptoGuide™ to guide this decision during consult.
What to check
- Visual acuity before instillation where possible.
- Pattern of redness: diffuse, sectoral, or ciliary.
- Cornea with fluorescein and cobalt blue illumination.
- Pupil shape and reactivity, plus anterior chamber reaction.
- Lids, lashes, discharge pattern, and relevant contact lens use.
When to refer
- Same day if keratitis, anterior uveitis, acute glaucoma, trauma, or vision loss is suspected.
- Urgent ophthalmology review for corneal ulceration, dendrites, hypopyon, or marked unilateral pain.
- Refer if symptoms are escalating or not fitting a benign surface picture.
Initial management
- Stabilise the likely site of pathology: lid margin, conjunctiva, cornea, or anterior chamber.
- Document acuity, staining, pupil findings, and photophobia clearly.
- Escalate early when the cornea or vision is involved rather than observing a painful red eye.
Clinical basis
This guidance reflects standard optometric clinical reasoning based on:
- Australian optometry clinical practice patterns
- Australian medicines regulation and PBS prescribing context
- Common ophthalmology referral standards
- Evidence-based clinical training and practice
Use OptoGuide™ during consult for structured clinical guidance.