Glaucoma testing includes a variety of tests that may indicate progressive damage to the optic nerve. Early detection and treatment of glaucoma is the best way to protect your vision from damage.
Each January we recognize Glaucoma Awareness Month. Glaucoma, a leading cause of blindness can be prevented with early detection, education and awareness.
Glaucoma testing includes these five tests:
- Tonometry to measure inner eye pressure
- Ophthalmoscopy to view the shape and color of the optic nerve
- Perimetry to measure your complete field of vision
- Gonioscopy to measure the angle in the eye where the iris meets the cornea
- Pachymetry to measure the thickness of the cornea
For contact tonometry eye drops are used to numb the eye. Then a tonometer is used to measure the resistance of your cornea to indentation. A small probe is used to gently press onto the eye to indent the cornea. The pressure that the cornea pushes back onto the tonometer is measured in millimeters of mercury. This measurement can be compared year-to-year to see if your eye pressure is increasing.
Non-contact tonometry is commonly referred to as the “air puff” test. It does not involve touching the eye. A puff of air is used to flatten the cornea and the pressure that the cornea pushes back with is measured.
Eye drops are used to dilate the pupil so your doctor can see through to the back of your eye to examine the shape and color of the optic nerve. If the optic nerve looks unusual then further testing will be done.
This exam determines if the angle where the iris meets the cornea is wide, or narrow, or closed. Eye drops are used to numb the eye and a handheld contact lens is placed on the eye. This contact lens has a mirror that shows the doctor the angle between the iris and cornea.
This is a visual field test that produces a map of your complete field of vision. This test will help determine whether your vision has been affected by glaucoma. During this test, you will be asked to look straight ahead as a spot of light is repeatedly presented in different areas of your peripheral vision and without moving your eyes you will tell your doctor when you are able to see the objects in your peripheral (side) vision.
A perimetry test is useful in finding early changes in vision caused by nerve damage from glaucoma. Regular perimetry tests can be used to see if treatment for glaucoma is preventing further vision loss.
This test is used to measure the thickness of your cornea—the clear protective outer layer of your eye. A probe called a pachymeter is gently placed on the front of the eye (the cornea) to measure its thickness. The pachymeter uses either ultrasonic or optical.
The optical pachymeter does not come in contact with the eye. The ultrasound pachymeter uses a probe that touches the cornea.
Why so Many Glaucoma Tests?
Diagnosing glaucoma is not always straightforward or easy. There are several factors that contribute to the diagnosis. Many patients have some features, but not all and are just borderline glaucoma.
Each person is unique, and a final diagnosis of glaucoma depends not just on the eye pressure, but on other factors too. Sometimes eye pressure is normal, but optic nerve damage is occurring. That is why careful structural and functional evaluation of the optic nerve is an essential part of diagnosing glaucoma.