Tests for Glaucoma
Five Common Glaucoma Tests
Early detection, through regular and complete eye exams, is the key to protecting your vision from damage caused by glaucoma.
A Comprehensive Glaucoma Exam
To be safe and accurate, five factors should be checked before making a glaucoma diagnosis:
- Examining the inner eye pressure
- Name of Test: Tonometry
- Examining the shape and color of the optic nerve
- Name of Test: Ophthalmoscopy (dilated eye exam)
- Examining the complete field of vision
- Name of Test: Perimetry (visual field test)
- Examining the drainage angle in the eye where the iris meets the cornea
- Name of Test: Gonioscopy
- Examining the thickness of the cornea
- Name of Test: Pachymetry
Regular glaucoma check-ups include two routine eye tests: tonometry and ophthalmoscopy
Tonometry measures the pressure within your eye. During tonometry, eye drops are used to numb the eye. Then a doctor or technician uses a tool called a tonometer to measure the inner pressure of the eye. A small amount of pressure is applied to the eye by a tiny tool or by a warm puff of air.
The range for normal pressure is 12-21 mm Hg (“mm Hg” refers to millimeters of mercury, a scale used to record eye pressure). Many glaucoma cases are diagnosed with high pressures exceeding 20mm Hg. However, some people can have glaucoma at pressures in the normal range. Eye pressure is unique to each person.
This diagnostic procedure helps the doctor examine your optic nerve for glaucoma damage. Eye drops are used to dilate the pupil, so the doctor can examine the shape and color of the optic nerve.
Perimetry is a visual field test that produces a map of your complete field of vision. This test will help a doctor determine whether your vision has been affected by glaucoma. During this test, you will be asked to look straight ahead and then indicate when a moving light passes your peripheral (or side) vision. This helps draw a “map” of your vision. After glaucoma has been diagnosed, visual field tests are usually done one to two times a year to check for any changes in your vision.
This diagnostic exam helps determine whether the drainage angle is narrow or closed.
Pachymetry is a simple, painless test to measure the thickness of your cornea — the clear window at the front of the eye. Corneal thickness has the potential to influence eye pressure readings. With this measurement, your doctor can better understand your IOP reading and develop a treatment plan that is right for you. The procedure takes only about a minute to measure both eyes.
Optic Nerve Imaging
Your doctor may use one of these optic nerve computer imaging techniques as a part of your glaucoma examination. By imaging your optic nerve over time, your doctor can help monitor and detect loss of optical nerve fibers. The following machines can measure nerve fiber height:
- The Heidelberg Retina Tomograph (HRT)
- The Nerve Fiber Analyzer (GDx)
- Optical Coherence Tomography (OCT)