# Red Eye: A Clinical Approach

> Red eye triage for NEET-PG Ophthalmology: conjunctival versus ciliary congestion, iritis, acute angle-closure glaucoma, keratitis, danger signs.

- Canonical URL: https://prepelephant.com/topics/neet-pg/ophthalmology/red-eye-approach
- Exam / course: NEET-PG · 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: "Red Eye: A Clinical Approach", PrepElephant, https://prepelephant.com/topics/neet-pg/ophthalmology/red-eye-approach

## Direct answer

Not every red eye deserves antibiotic drops. A red eye with normal vision, a clear cornea and no photophobia is almost always conjunctivitis; reduced vision, ciliary pain, photophobia, corneal opacity, a fixed or mid-dilated pupil or a stony-hard eye mark the dangerous causes — keratitis, anterior uveitis and acute angle-closure glaucoma. The single discriminant AK Khurana drills is conjunctival versus ciliary congestion: bright red, superficial, movable vessels that branch and are maximal in the fornices, against a dusky violet, deep, immobile circumcorneal flush with ciliary tenderness. Management flows from that split.

## What you must remember

- Conjunctival congestion: bright red, superficial vessels that move with the conjunctiva, maximal away from the limbus, mucoid or purulent discharge, vision normal — bacterial, viral or allergic conjunctivitis.
- Ciliary congestion: violet-red, deep circumcorneal vessels that do not move, with ciliary tenderness (pain on pressing over the ciliary body through the depressed lid) — keratitis, iritis or acute congestive glaucoma.
- Danger signs demanding same-day referral: vision below 6/18, severe pain, photophobia, corneal opacity or epithelial defect, hypopyon, keratic precipitates, a vertically oval fixed mid-dilated pupil, or raised intraocular pressure.
- Acute angle-closure glaucoma: halos around lights, steamy oedematous cornea, fixed semi-dilated pupil, intraocular pressure often 40–60 mmHg, hard globe; emergency treatment is intravenous acetazolamide with mannitol, topical pilocarpine once pressure falls, then Nd:YAG laser iridotomy.
- Iritis (anterior uveitis): ciliary flush, small irregular pupil, keratic precipitates, flare and cells in the anterior chamber, synechiae; treated with cycloplegics and topical corticosteroids.
- Discharge as a clue: mucopurulent in bacterial, watery with follicles and preauricular node in adenoviral, stringy with itching in allergic; hyperacute profuse purulent discharge with chemosis means gonococcal conjunctivitis — an ocular emergency.
- A red eye in a contact lens wearer is microbial keratitis until proved otherwise; stop the lens, stain with fluorescein, refer.

## Four red eyes at the slit lamp

Walk through four casualty arrivals and the pattern fixes itself. The first is a young man with bilateral watery redness, follicles in the lower fornix and a tender preauricular node — adenoviral follicular conjunctivitis; support with lubricants, warn about contagion for two weeks, no antibiotic needed. The second is a farmer with pain, photophobia and a white infiltrate that stains with fluorescein — a corneal ulcer; scrape before starting fortified antibiotics, because agricultural trauma in India is fungal until excluded. The third is a middle-aged woman with halos, a hazy cornea and a fixed vertically oval pupil at 50 mmHg — acute angle closure; bring the pressure down medically, then iridotomy, and prophylactic iridotomy in the fellow eye. The fourth has one ciliary-flushed eye, a small pupil, one-plus cells and flare and fine keratic precipitates — anterior uveitis; dilate with homatropine, start topical steroids after considering infection, and hunt the cause, tuberculosis first in India.

## Where students slip

Two errors dominate. The first is prescribing a steroid–antibiotic combination from the pharmacy for any red eye: in herpetic epithelial disease it converts a dendrite into a geographic ulcer, and unsupervised use raises intraocular pressure. The second is labelling acute angle closure as "severe conjunctivitis" because the cornea is hazy and vision poor — checking the pupil size and pressing the globe would have separated the two instantly. Examiners love a photograph of a ciliary flush with the question "which vessel layer, and what three diagnoses does it narrow to?"

## Frequently asked questions

### How do you differentiate conjunctival from ciliary congestion?

Conjunctival congestion is bright red, superficial, maximal in the fornices and movable with the conjunctiva; ciliary congestion is violet, deep, maximal at the limbus, immobile and accompanied by ciliary tenderness, pointing to keratitis, iritis or acute glaucoma.

### Which red eye presentations are true emergencies?

Acute angle-closure glaucoma, sight-threatening keratitis or corneal ulcer, gonococcal (hyperacute purulent) conjunctivitis, endophthalmitis and orbital cellulitis all need same-day specialist care.

### What pupil findings localise a red eye?

A fixed, vertically oval, mid-dilated pupil suggests acute angle closure; a small, irregular, poorly dilating pupil with synechiae suggests anterior uveitis; a dilated pupil with corneal haze and severe pain suggests raised pressure or iris ischaemia.

### Why are topical steroids dangerous in an undiagnosed red eye?

They worsen herpes simplex epithelial keratitis, favour fungal and bacterial multiplication, cause steroid-induced glaucoma and cataract, and mask progression — reserve them for proven non-infectious inflammation under supervision.

### What is ciliary tenderness and what does it indicate?

Pain on gentle pressure over the ciliary body region through the closed lid, indicating inflammation of the deeper coats — uveitis, keratitis or glaucoma — rather than surface conjunctival disease.

### Which red eye presents with preauricular lymphadenopathy?

Adenoviral follicular conjunctivitis (pharyngoconjunctival or epidemic keratoconjunctivitis) classically, and also gonococcal, chlamydial and Parinaud oculoglandular conjunctivitis.