label: Failure of phenylephrine to induce blanching of eye redness
label_lc: failure of phenylephrine to induce blanching of eye redness
description: "Instillation of 2.5% phenylephrine drops into the eye does not induce blanching of eye redness. Failure to blanch suggests redness caused by scleral vessel engorgement (e.g., scleritis) or extravascular cause (e.g., hemorrhage), not episcleritis or conjunctivitis."