According to the National Eye Institute, glaucoma is an eye disease that occurs when the fluid pressure inside the eye increases to a level that causes damage to the optic nerve. The optic nerve connects the light-sensitive tissue at the rear of the eye to the brain, and a damaged optic nerve can lead to vision loss or even blindness. Any person can have glaucoma, but people over the age of 60 and African-Americans over the age of 40 are at especially high risk for the disease.
Tonometry
Tonometry is a vision test that can determine the pressure inside the eye, according to Harvard Health Publications. An eye doctor administers the test by having the patient look closely at an instrument that sends a puff of air to the front of the eye. This causes a depression in the cornea that the instrument can measure. The instrument itself does not come in contact with the eye, and test results are available immediately.
Hospital emergency room personnel can measure the pressure inside a patient's eye with a device that looks like a pen. The measurement is taken when the health care professional places one end of the device onto the surface of the eye.
Ophthalmoscopy
According to the University of California at San Francisco Medical Center, ophthalmoscopy is an eye exam that studies the condition of tissue at the back part of the eye. During this exam, the eye doctor is looking for signs of retinal detachment, optic nerve damage that results from glaucoma, or evidence of leaking blood vessels. The direct ophthalmoscopy procedure is carried out in a darkened room and may or may not involve dilation of the pupil. The ophthalmoscope resembles a flashlight in size, and has a light source and a set of lenses. The doctor shines the light through the pupil to reveal the back of the eye, and the lenses are used to bring the eye parts into focus. In the indirect ophthalmoscopy procedure, the doctor dilates the pupil and can view the entire retina by holding the patient's eye open and wearing a head instrument that looks like a miner's light. The light that the doctor focuses into the eye is much brighter than the one used in the direct process.
Visual Field (Perimetry) Tests
Peripheral vision enables a person to see objects that are positioned on the left or right side. One of the first signs of glaucoma is a decline in the peripheral visual fields, according to the University of Maryland Medical Center. A doctor uses perimetry tests to determine how good a patient's peripheral vision is. In these tests, the patient focuses straight ahead and must tell the doctor when a moving light is visible at the side.
