Glaucoma Diagnosed
How is glaucoma diagnosed?
Individuals at high risk for glaucoma should have a dilated pupil eye examination at least every two years. Eye doctors use several tests to detect glaucoma; these tests include:
- Tonometry measures the pressure inside the eye. Examples of tonometers include: 1) The air puff or noncontact tonometer emits a puff of air. Eye pressure is measured by the eye’s resistance to the air. 2) The applanation tonometer touches the eye’s surface after the eye has been numbed, and measures the amount of pressure necessary to flatten the cornea. This is the most sensitive tonometer, but a clear, regularly-shaped cornea is needed for it to function properly. 3) The electronic indentation method measures pressure by directly contacting anesthetized eyes with a digital pen-like instrument.
- In pupil dilation, special drops temporarily enlarge the pupil so that the doctor can better view the inside of the eye.
- Visual field testing measures the entire area seen by the forward-looking eye to document straight-ahead (central) and/or side (peripheral) vision. It measures the dimmest light seen at each spot tested. Each time a flash of light is perceived, the patient responds by pressing a button.
- A visual acuity test measures sight at various distances. While seated 20 feet from an eye chart, the patient is asked to read standardized visual charts with each eye, with and without corrective lenses.
- Pachymetry uses an ultrasonic wave instrument to help determine the thickness of the cornea and better evaluate eye pressure.
- Ophthalmoscopy allows the doctor to examine the interior of the eye by looking through the pupil with a special instrument. This can help detect damage to the optic nerve caused by glaucoma.
- Gonioscopy allows the doctor to view the front part of the eye (anterior chamber) to determine if the iris is closer than normal to the back of the cornea. This test can help diagnose closed-angle glaucoma.
- Optic nerve imaging helps document optic nerve changes over time. An eye doctor may choose to use one or more of the four available scanning techniques, all of which are painless and non-invasive.
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