Which statement regarding glaucoma is true?

Glaucoma is the leading cause of irreversible blindness in the world. When sufficient axinal loss occurs, peripheral vision declines. Loss of central vision occurs much later in the disease process. Retinopathy due to glaucoma is irreversible. Treatment is focused on lowering intraocular pressure. Reduction in intracecular pressure has been demonstrated to protect against fuher damage to the optic nerve. Primary open-angle is by far the most common type of glaucoma in the United States. Closed-angle glaucoma is more common among Asians. The Schijltz tonometer, due to the fact that it is inexpensive, is the most frequently used device to measure intraoccular pressure in the United States. It is used in both hospitals and outpatient clinics. b-Adrenergic antagonists are one of the more commonly used drugs and are initially staed as a topical agent. Unfounately, excess drug drains through the nasolacrimal duct into the nose and is absorbed into the systemic circulation. Therefore systemic side effects can occur and may be severe. It is not unusual for patients to be treated with a bronchodilater drug for new-onset bronchospasms without the physician considering the use of topical b-adrenergic antagonist, used for glaucoma treatment, which may have contributed to the condition.