D-Timolol maleate is primarily used in the treatment of glaucoma and ocular hypertension. It works by reducing the production of aqueous humor in the eye, thereby lowering intraocular pressure. This helps in preventing damage to the optic nerve and preserving vision. It is often administered in the form of eye drops for direct and effective action. Additionally, it may be used in some cases to manage conditions like migraines and certain types of heart arrhythmias, although these applications are less common. Always consult a healthcare professional for appropriate use and dosage.