TABLE 27.1 COMMON CAUSES OF RED EYE a Conjunctivitis Infectious: viral (including herpes), bacterial, chlamydial Allergic or seasonal Chemical (or other physical agents such as smoke) Systemic disease (Table 27.3 ) Trauma Corneal or conjunctival abrasion Iritis Foreign body Subconjunctival hemorrhage Dry eye syndromes Abnormalities of the lids and/or lashes Blepharitis Trichiasis due to epiblepharon Stye or chalazion (external or internal hordeolum) Molluscum of lid margin Periorbital or orbital cellulitis Contact lens–related problems Infectious keratitis (corneal ulcer) Allergic conjunctivitis Corneal abrasion Poor fit Overwear a Not listed in order of frequency List not complete Direct ocular trauma may result in a red eye due to corneal or conjunctival abrasion, hyphema, iritis, or rarely, traumatic glaucoma (see Chapter 114 Ocular Trauma ) If there is no fluorescein staining of the conjunctiva or cornea and there is no evidence of severe intraocular injury such as hyphema or ruptured globe, the examiner should consider the possibility of noxious material coming in contact with the eyeball at the time of trauma Both acidic and alkaline substances may cause a red eye (see Chapter 123 Ophthalmic Emergencies ) Likewise, a foreign body may cause ocular pain and inflammation Foreign bodies often can be difficult to see on brief, superficial examination, especially if the foreign body is smaller than what the naked eye can see All the recesses and redundant folds of the conjunctiva must be inspected The upper eyelid should be everted (see Chapter 114 Ocular Trauma ) The lower eyelid should be pulled down from the globe as the patient looks upward so the inferior fornix can be inspected The patient should be asked to adduct the affected eye when the lateral canthus is stretched laterally to allow inspection of the lateral fornix There is no analogous medial fornix In addition to direct trauma, head injury can rarely cause the development of an intracranial arteriovenous fistula that may present with proptosis, chemosis, red eye, corkscrew conjunctival blood vessels, and decreased vision TABLE 27.2 LIFE-THREATENING CAUSES OF RED EYE a Systemic disease (Table 27.3 ) Child abuse Blunt trauma Covert instillation of noxious substances (medical child abuse [Munchausen syndrome by proxy]) Traumatic intracranial arteriovenous fistula (very rare) a List not meant to be complete TABLE 27.3 SYSTEMIC CONDITIONS THAT MAY BE ASSOCIATED WITH RED EYE a Collagen vascular disorders Juvenile idiopathic arthritis Infectious diseases HSV, varicella zoster, measles, otitis media Kawasaki disease Inflammatory bowel disease Cystic fibrosis Vitamin A deficiency Cystinosis Leukemia Ectodermal dysplasia Trisomy 21 Cornelia de Lange syndrome History of radiation therapy, including ocular field History of bone marrow transplantation or graft-versus-host disease Stevens–Johnson syndrome a Not a complete list: intended to demonstrate multiorgan representation The position of the eyelashes should be inspected before performing lid eversion and examining the conjunctival fornices Eyelashes that turn against the ocular surface (trichiasis) may cause a red eye that is accompanied by pain or foreign body sensation in the absence of lid swelling Corneal fluorescein staining from the lashes abrading the corneal epithelium may be so mild that it can only be detected by slit-lamp biomicroscopy, even in symptomatic patients Trichiasis is particularly common in patients who have had prior injury or surgery to the eyelid and in patients of Asian background In the latter case, a prominent fold of skin (epiblepharon) may be found medially just below the eyelid margin, causing the lower lid medial eyelashes, and less commonly the upper lid lashes, to rotate toward the eyeball FIGURE 27.1 Pseudomembrane on lower lid palpebral conjunctiva and extending into the inferior fornix in patient with epidemic keratoconjunctivitis (adenovirus)