Timolol is a non-specific beta-blocking agent acting on both beta 1 and beta 2 receptors while metoprolol is a specific beta 1 blocking agent. Both timolol and metoprolol decrease intraocular pressure by reducing aqueous humor secretion without increasing facility of outflow. They have both similar short and long term efficacy which does not diminish even after several months of use. Generally, there are adequate to treat glaucoma without perimetric changes, while treatment of glaucoma with functional defects requires their association with miotics. When blocking beta 1 receptors, timolol causes marked constriction of bronchi and peripheral vessels. Hence, it is contraindicated in bronchial asthma and ischemic optic neuropathy. This is not the case with metoprolol, which does not block beta 2 receptors.