Used primarily as an antihistamine in ophthalmic preparations to relieve allergic conjunctivitis symptoms such as redness, itching, and swelling of the eyes. It works by blocking histamine receptors and reducing the allergic response. Often combined with other agents like vasoconstrictors or mast cell stabilizers in eye drops for enhanced relief. Also exhibits mild anti-inflammatory and local anesthetic properties, contributing to its effectiveness in treating eye irritation.