Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.

A 25-year-old woman presents for evaluation of recurrent, bilateral eye pain and redness. Symptoms began several months ago without a specific inciting event. With each episode, she has deep or boring pain that is constant and has awakened her from sleep. She has had photophobia, tearing, and decreased vision during the episodes.

Vital signs are normal. Visual acuity is 20/40 bilaterally. There is photophobia. The pupils are equal, round, and reactive to light. Extraocular movements are intact but painful. The corneas appear clear. On the lateral aspect of both eyes, there is a localized area of raised erythema, with superficial blood vessels coursing over top of erythema but no white sclera visible between the blood vessels. There is no discharge or crusting of the lids.

Which of the following is the most likely diagnosis regarding her eyes?

A) Episcleritis
B) Scleritis
C) Subconjunctival hematoma
D) Uveitis
E) Viral conjunctivitis

MKSAP Answer and Critique

The correct answer is B) Scleritis. This item is available to MKSAP 15 subscribers as item 17 in the General Internal Medicine section. More information about MKSAP 15 is available online.

Painful red eye should prompt consideration of conjunctivitis, episcleritis, scleritis, keratitis or corneal ulcer, iritis, endophthalmitis, uveitis, and glaucoma. This patient has severe bilateral eye pain that is described as deep and boring, has awakened her from sleep, and has associated photophobia, tearing, and eye findings of erythema localized to the sclera. The most likely diagnosis is scleritis.

Scleritis is a serious eye condition that can lead to permanent visual loss or globe rupture and should be treated urgently in consultation with an ophthalmologist. Nearly half of patients with scleritis have an underlying systemic problem, often a connective tissue disease.

Episcleritis is an inflammation of the superficial blood vessels overlying the sclera. Patients may present with no symptoms or mild ocular pain and redness, which may occur abruptly. The blood vessels appear prominent and engorged, but normal white sclera may be visible between the blood vessels, helping to distinguish this from scleritis. This patient’s severe pain and raised erythematous lesions make scleritis the more likely diagnosis.

Subconjunctival hematoma causes an often well-localized area of bright erythema that overlies but does not involve the sclera. It causes a painless red eye and resolves spontaneously and does not affect visual acuity. This patient’s red eyes are associated with diminished visual acuity and severe pain and involve the sclera, ruling out subconjunctival hematoma.

Patients with anterior uveitis present with the abrupt onset of eye pain and redness. The redness is typically adjacent and circumferential to the iris. Patients may have photophobia, tearing, decreased vision, and headache. As the inflammation involves the iris and ciliary body, patients may have an irregular pupil. Uveitis requires emergency ophthalmology consultation. The patient’s focal inflammation and equal pupils make anterior uveitis an unlikely diagnosis.

Viral conjunctivitis can present with the abrupt onset of diffuse conjunctival erythema and injection associated with a foreign body sensation and discharge. This patient’s deep, severe pain and localized, raised erythema and diminished visual acuity are more consistent with scleritis.

Key Point

• Patients with a severely painful, red eye should be considered to have a sight-threatening condition until proven otherwise.

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