Table 1.

Selected Nonconjunctivitis Causes of Red Eye^a

Differential Diagnosis	Symptoms	Penlight Examination Findings
Dry eye disease	Burning and foreign-body sensation. Symptoms are usu- ally transient, worse with prolonged reading or watching television because of decreased blinking. Symptoms are worse in dry, cold, and windy environments because of increased evaporation.	Bilateral redness
Blepharitis	Similar to dry eyes	Redness greater at the margins of eyelids
Uveitis	Photophobia, pain, blurred vision. Symptoms are usually bilateral.	Decreased vision, poorly reacting pupils, constant eye pain radiating to temple and brow. Redness, severe photophobia, presence of inflammatory cells in the anterior chamber.
Angle closure glaucoma	Headaches, nausea, vomiting, ocular pain, decreased vision, light sensitivity, and seeing haloes around lights. Symptoms are usually unilateral.	Firm eye on palpation, ocular redness with limbal injec- tion. Appearance of a hazy/steamy cornea, moderately dilated pupils that are unreactive to light.
Carotid cavernous fistula	Chronic red eye; may have a history of head trauma	Dilated tortuous vessels (corkscrew vessels), bruits on auscultation with a stethoscope
Endophthalmitis	Severe pain, photophobia, may have a history of eye sur- gery or ocular trauma	Redness, pus in the anterior chamber, and photophobia
Cellulitis	Pain, double vision, and fullness	Redness and swelling of lids, may have restriction of the eye movements, may have a history of preceding sinus- itis (usually ethmoiditis)
Anterior segment tumors	Variable	Abnormal growth inside or on the surface of the eye
Scleritis	Decreased vision, moderate to severe pain	Redness, bluish sclera hue
Subconjunctival hemorrhage	May have foreign-body sensation and tearing or be asymptomatic	Blood under the conjunctival membrane

^aData are from Cronau et al¹⁸ and Leibowitz.¹ The examination can be done by shining a penlight in the patient’s affected eye(s).