In the treatment of glaucoma, your eye doctor will try to reduce the risk of damage to your optic nerve by keeping your eye pressure (intraocular pressure, or IOP) from rising above a certain level. That level of pressure is called your target pressure. By reducing the risk of optic nerve damage, maintaining the target pressure in your eyes may help slow the progression of the disease.
A tonometry test is used to measure the pressure in the eyes. The target pressure is based on the degree of optic nerve damage, the amount of visual field loss and, to a lesser degree, the initial pressure in the eye and how widely it varies each time it is measured. The target pressure varies from person to person. It is usually about 20% to 30% less than the highest IOP you've had.
When the tonometry measurement is above target pressure, your doctor will consider making changes to your treatment, such as starting medicine or changing your medicine.