Opticrom (cromolyn sodium ophthalmic solution, USP) 4% is a clear, colorless, sterile solution intended for topical ophthalmic use. Opticrom is indicated in the treatment of vernal keratoconjunctivitis, vernal conjunctivitis, and vernal keratitis. It prevents itching of the eyes that can occur with these conditions. Cromolyn is known as a mast cell stabilizer. It works by blocking certain natural substances (histamine, SRS-A) that cause allergic symptoms.