🩺 Red Eye

Red eye is a common clinical presentation caused by the vasodilation of the conjunctival, episcleral, or scleral vessels. While many causes like conjunctivitis or subconjunctival haemorrhage are benign and self-limiting, others are sight-threatening emergencies. Clinical differentiation relies heavily on the presence of pain, changes in visual acuity, and the specific distribution of redness. Accurate diagnosis is essential to ensure life-changing conditions like acute glaucoma or microbial keratitis are referred urgently to ophthalmology.

Key diagnostic questions include: Is there pain? Is the vision affected? Is there discharge? Painful red eye with vision loss suggests serious pathology (glaucoma, uveitis, keratitis). A gritty, painless red eye with discharge suggests conjunctivitis (purulent for bacterial, watery for viral). Ask about contact lens wear (high risk for Pseudomonas keratitis) and any history of trauma or chemical exposure. Inquire about systemic symptoms such as joint pain or photophobia.

Assess visual acuity using a Snellen chart (with correction). Perform a penlight exam for pupil size and reactivity, and check the pattern of redness (diffuse, localized, or circumscribed). Use fluorescein staining to look for corneal abrasions or dendritic ulcers (HSV). Assess for corneal clarity (haziness suggests glaucoma or keratitis). Evert the lids to check for foreign bodies or follicles/papillae. Measure intraocular pressure if glaucoma is suspected and equipment is available.

Conjunctivitis (Bacterial, Viral, Allergic), Episcleritis, Scleritis, Anterior Uveitis (Iritis), Acute Angle-Closure Glaucoma, Corneal Abrasion/Ulcer, and Subconjunctival Haemorrhage.

Reduced visual acuity, severe deep-seated eye pain, photophobia, ciliary flush, corneal clouding, and a history of penetrating trauma or chemical injury.

Most cases are diagnosed clinically. Fluorescein staining is essential in primary care/A&E to exclude corneal ulcers. Eye swabs for culture and sensitivity are indicated for severe or neonatal conjunctivitis. Referral for slit-lamp examination by ophthalmology is required for suspected uveitis, scleritis, or keratitis. If acute angle-closure glaucoma is suspected, urgent tonometry is necessary.

'Ciliary flush' (redness concentrated around the cornea) is a sign of deep inflammation (keratitis, uveitis, glaucoma) and is a 'must-not-miss'. A pupil that is mid-dilated and fixed suggests acute angle-closure glaucoma, while a small, irregular pupil suggests uveitis. Always check visual acuity in every red eye patient—reduced acuity is a major red flag.

Aligned with 'The Red Eye' and 'Acute Visual Loss'. Students must be able to identify conditions requiring emergency 24-hour referral (glaucoma, uveitis, keratitis) versus those manageable in primary care (conjunctivitis, episcleritis). Recognize the risk of steroid-induced cataracts and glaucoma.