# The Red Eye > The red eye for FMGE Ophthalmology: triage of conjunctivitis, keratitis, uveitis, acute glaucoma and scleritis using vision, pain, pupil and pressure. - Canonical URL: https://prepelephant.com/topics/fmge/ophthalmology/red-eye-fmge - Exam / course: FMGE · Subject: Ophthalmology - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "The Red Eye", PrepElephant, https://prepelephant.com/topics/fmge/ophthalmology/red-eye-fmge ## Direct answer Most red eyes that walk into an Indian outpatient department are conjunctivitis, but the five that matter — keratitis, anterior uveitis, acute angle-closure glaucoma, scleritis and endophthalmitis — announce themselves through four discriminators: visual acuity, the pattern of injection, the pupil, and intraocular pressure. Discharge with normal vision and a comfortable pupil is conjunctivitis; a hazy, stained cornea with ciliary flush is keratitis; a small painful pupil with cells and flare is uveitis; a fixed semidilated pupil with a steamy cornea and pressure above 40 mmHg is acute glaucoma; and a red eye after surgery or trauma with hypopyon is endophthalmitis until excluded. Fluorescein staining, tonometry and a slit lamp convert a symptom into a diagnosis within minutes. ## What you must remember - Reduced vision is the single red flag that removes a red eye from the "simple" category — conjunctivitis sees 6/6; keratitis, uveitis and glaucoma do not. - Diffuse injection maximal in the fornices suggests conjunctivitis; deep ciliary flush around the limbus signals corneal or intraocular disease; pupil clues follow — small, irregular and sluggish in anterior uveitis, fixed and mid-dilated in acute angle closure, normal in conjunctivitis and episcleritis. - Fluorescein staining finds the corneal epithelial break — dendritic in herpes simplex, a round infiltrate in bacterial keratitis, a linear abrasion after trauma. - Acute angle-closure glaucoma presents with pain, haloes around lights, nausea and a hard eye; it is the red eye most often mistaken for migraine or gastritis. - Scleritis is a deep, boring, night-time pain in a sectoral violet discolouration, often with systemic disease such as rheumatoid arthritis or vasculitis; episcleritis is mild, sectoral and self-limiting. - Postoperative or post-traumatic red eyes are endophthalmitis until proven otherwise — pain and hypopyon demand urgent vitreous assessment. - Subconjunctival haemorrhage — a flat, bright-red patch with normal vision and a clear cornea — is dramatic but benign, and recurrent bilateral cases warrant a bleeding history and blood pressure check. - Never pad a discharging eye, never prescribe steroids for an undiagnosed red eye, and never dilate an eye with a shallow anterior chamber and a suspect angle. ## Reasoning through four red eyes side by side Place the four classic differentials in a row and let the discriminators work. First, a young man with bilateral watery redness, morning lid sticking, tender preauricular node and 6/6 vision: injection is fornix-deep, the cornea stains clear, the pupils react — adenoviral conjunctivitis; treatment is hygiene and reassurance. Second, a contact lens wearer with unilateral pain, photophobia and 6/18 vision: the flush is limbal, fluorescein shows a central stain with an infiltrate and a hypopyon — bacterial keratitis; scrape and start fortified antibiotics hourly. Third, a woman with unilateral aching photophobia and 6/24 vision: the pupil is small and sticky, keratic precipitates line the endothelium and cells thread the aqueous — anterior uveitis; cycloplegia and topical steroids, then a cause hunt. Fourth, an elderly woman with evening pain, vomiting and blurred vision with rainbow rings: the cornea is oedematous, the pupil fixed at mid-dilation, the anterior chamber shallow and the pressure 50 mmHg — acute angle closure; acetazolamide, timolol and mannitol before pilocarpine, then iridotomy. Notice that the same triad — pain, redness, reduced vision — resolves differently by asking only four questions: how well does the eye see, where is the redness deepest, what is the pupil doing, and what does the tonometer say. ## Where candidates slip The recurring clinical error in Indian practice is the over-the-counter steroid-combination drop for an undiagnosed red eye, which converts adenoviral conjunctivitis into a prolonged keratitis and a herpetic dendrite into a geographic ulcer. The exam version of the same error is listing drug names before naming the diagnosis. A second slip is dilating every red eye for fundus examination — in a shallow-chamber elderly eye, mydriasis can precipitate the very angle closure being excluded. The third is forgetting the systemic thread: a boring scleritis with joint pain is rheumatoid arthritis speaking, and a red eye with oral ulcers and genital ulcers is Behçet disease, answers that earn the extra mark. ## Frequently asked questions ### Which single finding makes a red eye dangerous? Reduced visual acuity, which excludes simple conjunctivitis and points to keratitis, uveitis, glaucoma or endophthalmitis. ### How does the pupil differ in uveitis and acute angle closure? Uveitis constricts the pupil — small, irregular and sluggish with posterior synechiae — while angle closure fixes it in mid-dilation with a steamy cornea and raised pressure. ### What does ciliary flush indicate? Deep injection concentrated around the limbus, signifying corneal or intraocular inflammation such as keratitis or anterior uveitis, not surface conjunctival disease. ### Which red eye is mistaken for an acute abdomen or migraine? Acute angle-closure glaucoma, with severe headache, nausea and vomiting accompanying a painful red eye with haloes. ### How are episcleritis and scleritis distinguished? Episcleritis is mild, sectoral, pink and self-limiting; scleritis is a deep, boring pain with violet discolouration, tenderness and associations such as rheumatoid arthritis and Wegener granulomatosis.