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Difficulty: EasyFormulating a Differential Diagnosis

A clinician is evaluating several patients presenting to the urgent care clinic with a primary complaint of a 'red eye'. Match each of the following classic ocular presentations with its most likely primary differential diagnosis.

  • Unilateral red eye, severe pain, seeing halos around lights, fixed mid-dilated pupil, and a cloudy corneaAcute angle-closure glaucoma
  • Bilateral red eyes, severe itching, watery discharge, and cobblestone papillae on the upper tarsal conjunctivaAllergic conjunctivitis
  • Unilateral red eye, severe pain, photophobia, and a branching dendritic corneal ulcer seen on fluorescein stainHerpes simplex keratitis
  • Unilateral red eye, purulent discharge, crusting of lashes in the morning, and normal visual acuity without photophobiaBacterial conjunctivitis

Answer

Presentation 1 matches Acute angle-closure glaucoma. Presentation 2 matches Allergic conjunctivitis. Presentation 3 matches Herpes simplex keratitis. Presentation 4 matches Bacterial conjunctivitis.
Each presentation contains classic pathognomonic or highly specific findings that accurately differentiate the major causes of a red eye: purulent discharge points to a bacterial etiology, severe itching to an allergic etiology, a dendritic ulcer to HSV keratitis, and a fixed mid-dilated pupil with halos to acute angle-closure glaucoma.

Step-by-Step Solution

1
Analyze the first presentation, noting the fixed mid-dilated pupil, severe pain, and halos around lights.
Identified as a sign of rapidly increased intraocular pressure and subsequent corneal edema.
These are hallmark signs of acute angle-closure glaucoma, an ophthalmologic emergency.
2
Analyze the second presentation, noting severe itching and cobblestone papillae on the conjunctiva.
Identified as an immune-mediated hypersensitivity reaction.
Intense itching and cobblestoning are classic, differentiating features for allergic conjunctivitis.
3
Analyze the third presentation, noting the dendritic ulcer on fluorescein stain with photophobia.
Identified as a specific viral infection of the cornea.
Dendritic ulcers are pathognomonic for Herpes simplex keratitis.
4
Analyze the fourth presentation, noting purulent discharge without visual impairment or photophobia.
Identified as a superficial bacterial infection.
Purulent discharge without signs of deeper involvement (such as vision loss or severe pain) is typical of uncomplicated bacterial conjunctivitis.

Key Concept

Formulating a differential diagnosis for a 'red eye' based on distinguishing clinical features such as discharge type, presence of pain, visual acuity changes, and specific physical examination findings.
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Topics

Formulating a Differential Diagnosis

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