Red Eye: Differential

Key points

• Conjunctivitis: diffuse redness, discharge, NORMAL vision and pupils; viral (watery, pre-auricular node), bacterial (purulent), allergic (itchy, bilateral).
• Anterior uveitis (iritis): painful red eye, photophobia, small irregular pupil, ciliary flush; associated with HLA-B27 conditions.
• Keratitis/corneal ulcer: pain, photophobia, reduced vision; contact lens wearers — think acanthamoeba/Pseudomonas.
• Episcleritis: sectoral redness, mild discomfort, normal vision — usually self-limiting; scleritis: deep boring pain, violaceous hue — associated with RA/vasculitis.
• Subconjunctival haemorrhage: dramatic painless red patch, normal vision — reassurance; check BP.

Decision points in this pathway

• Vision normal + discharge + normal pupils?

The full step-by-step algorithm, including what to do at each branch, opens in the app for approved members.