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Red eye is caused by dilated conjunctival vessels or subconjunctival hemorrhage. The most common cause is infectious or allergic conjunctivitis; the most serious cause is closed-angle glaucoma, followed by uveitis, corneal ulcers, and scleritis (see Table 2: Approach to the Ophthalmologic Patient: Differential Diagnosis of Red Eye). Other causes include foreign bodies, trauma, episcleritis, keratitis, retrobulbar processes (often also causing exophthalmos), hordeola, and subconjunctival hemorrhage.

Table 2
Differential Diagnosis of Red Eye This table is presented as a PDF and requires the free Adobe PDF reader. Get Adobe Reader

Red eye usually coexists with pain, headache, or nausea and vomiting when caused by closed-angle glaucoma. It often coexists with discharge and crusting when caused by infectious conjunctivitis. Abrupt onset of red eye alone suggests trauma or direct eye irritation. Preauricular lymphadenopathy suggests viral conjunctivitis. Itching and watery discharge suggest allergic conjunctivitis. Scratchiness or a foreign body sensation suggests corneal abrasion, conjunctivitis, or keratoconjunctivitis sicca. A deep ache may also indicate scleritis. Halos or rainbow-like fringes suggest corneal edema. Photophobia suggests a corneal abrasion, corneal ulcer, or uveitis.

Diminished visual acuity suggests significant pathology, including glaucoma, corneal ulcer, hyphema from trauma, and uveitis. Discharge suggests allergic or viral (watery) or bacterial (purulent) conjunctivitis. Exophthalmos suggests a retrobulbar process, such as an abscess, orbital tumor, or Graves' disease. An irregular corneal light reflex suggests corneal edema, possibly due to acute closed-angle glaucoma, or a damaged corneal surface, possibly due to abrasion or keratitis. Ciliary flush suggests uveitis, glaucoma, or keratitis. Elevated intraocular pressure is diagnostic of glaucoma. Pupil irregularity or a midpoint fixed pupil may be due to uveitis or glaucoma (or to a neuro-ophthalmic problem).

No tests are necessary for patients with features strongly suggestive of allergic or viral conjunctivitis or subconjunctival hemorrhage. Others should generally undergo slit-lamp examination, tonometry, and fluorescein staining. CT or ultrasound is indicated to evaluate a suspected foreign body or, more rarely, to identify intraocular or orbital pathology.

Treatment is management of the underlying condition. Redness itself is rarely treated (eg, with vasoconstrictors) without a specific diagnosis.

Last full review/revision November 2005

Content last modified November 2005