A patient presents with a painless red eye and a localized red patch on the sclera with normal vision. Which diagnosis is most likely?

• A. Conjunctivitis
• B. Glaucoma
• C. Subconjunctival hemorrhage
• D. Acute iritis

Answer: (C)

The main idea is a painless, localized red patch on the white of the eye with preserved vision points to a subconjunctival hemorrhage. This occurs when a small blood vessel breaks beneath the conjunctiva, producing a sharp, well-demarcated red patch that looks dramatic but causes no pain, discharge, or vision loss. The eye otherwise feels normal, and intraocular pressure remains unaffected, which helps distinguish it from conditions that do affect vision or cause pain.

Why this fits best: there’s a conspicuous, localized patch rather than diffuse redness, and vision is intact. Subconjunctival hemorrhage often follows minor trauma, coughing, sneezing, or strain and typically resolves on its own over one to two weeks.

Why the others don’t fit as neatly: conjunctivitis usually causes diffuse conjunctival redness with discharge or irritation; glaucoma presents with a red eye plus pain, halos around lights, and reduced vision; acute iritis involves pain, photophobia, decreased vision, and a ciliary flush rather than a simple localized patch.