Glaucoma is the leading cause of irreversible blindness. Its leading symptom and the most important initial link of the disease pathogenesis is represented by an increase of intraocular pressure (IOP). Decrease of IOP is a basic notion in the therapy of glaucoma. Drug-induced therapy is currently the most widely spread initial intervention to decrease IOP. Prostaglandin analogues are referred to the basic group of pharmacotherapeutic agents, because they are the most effective and well tolerated. Beta-blocking agents are selected as an alternative. Other medicinal products to treat glaucoma include inhibitors of carbonic anhydrase for systemic (acetazolamide and methazolamide) and local (dorzolamide and brinzolamide) use. Systemic inhibitors of carbonic anhydrase are, on the one hand, more active than non-systemic medicinal preparations, and, on the other hand, have numerous side effects which are not safe for humans. Thus, medicinal preparations for local use are most frequently applied in the therapy of glaucoma. If necessary, they are combined with beta-blocking agents or alpha-adrenergic agonists.