Conquer NBEO Ocular Disease 2026 – Ace Part 1 & See Your Optometry Future Clear!

Phenylephrine 2.5% is used to differentiate episcleritis from scleritis by targeting the superficial vessels. In episcleritis, the problem is in the superficial episcleral vessels, so they blanch with phenylephrine as the vessels constrict. In scleritis, the inflammation lies deeper in the sclera, so the deeper scleral vessels don’t blanch and appear more stubborn to the drug. Therefore the statement claiming blanching occurs in scleritis vessels but not episcleritis vessels is not true; the opposite happens—episcleral vessels blanch in episcleritis, while scleral vessels typically do not blanch in scleritis.

For context, episcleritis is usually unilateral and sectoral and tends to be less painful, while scleritis is less common but more painful and can be bilateral or more diffuse, often requiring prompt systemic management if severe.