Posted by: Eye Health Northwest in Glaucoma on September 8, 2026
Glaucoma often develops without obvious symptoms. Your vision may seem normal for years, even as pressure slowly harms the optic nerve. That is why glaucoma is sometimes called the “silent thief of sight.”
To detect it early, eye doctors use several tests together, since no single test can give a complete picture. Keep reading to learn more about 6 tests the experts at EyeHealth Northwest use to check for glaucoma during an eye exam.
Why Is Glaucoma So Easy to Miss?
Glaucoma harms the optic nerve, which carries visual signals from your eye to your brain. The damage often begins at the edges of your side vision, an area most people do not notice. This means early vision loss can go undetected for years.
Once you notice gaps in your vision, the lost nerve tissue cannot be restored. That is why regular glaucoma screenings are essential to protecting your vision. Here are six tests you can expect at your eye exam that help your eye doctor diagnose glaucoma:
1. Tonometry
Tonometry measures the pressure inside your eye. This test is essential for glaucoma screening, as high intraocular pressure is the most common risk factor for optic nerve damage.
Your eye doctor may use a puff of air or gently touch your eye with a small probe to get a reading. However, some people can sustain optic nerve damage even with normal eye pressure, which is why eye doctors never rely on this test alone.
2. Pachymetry
Pachymetry uses an ultrasound probe to measure how thick your cornea is. This matters because corneal thickness affects how accurate the eye pressure reading is.
If your cornea is thinner, the pressure may seem lower than it really is. If it is thicker, the pressure may look higher. This test helps your eye doctor interpret your tonometry results correctly.
3. Ophthalmoscopy
Once your eyes are dilated, your eye doctor uses an ophthalmoscope to look directly at your optic nerve. They check for cupping, which is when nerve fibers are lost and the center of the optic disc becomes larger and deeper.
Cupping is often one of the first visible signs of glaucoma, sometimes showing up before you notice any symptoms. By comparing how your optic nerve looks over several years, doctors can spot changes that might not be obvious in just one visit.
4. Visual Field Testing
Visual field testing, or perimetry, has you look at a fixed point and respond to small flashing lights. This creates a map showing where your vision is strong and where there are blind spots, especially at the edges. Because glaucoma often affects side vision first, this test can detect vision loss you may not notice yourself.
5. Gonioscopy
Gonioscopy uses a special lens to let your eye doctor see the angle where your iris meets your cornea. This is where fluid drains from your eye to maintain healthy eye pressure.
The test helps determine what type of glaucoma you may have. If the angle is open but drainage is still restricted, it points to open-angle glaucoma, which is the most common type in the United States. A narrow drainage angle suggests angle-closure glaucoma, which can progress more quickly and sometimes requires different treatments.
6. OCT Imaging
Optical coherence tomography, or OCT, creates a detailed cross-sectional image of the optic nerve and surrounding nerve fiber layer, detecting thinning with a precision the human eye cannot match during a standard exam. Because OCT produces measurable, repeatable data, eye doctors can compare scans year over year and catch progression before it shows up on a visual field test.
Why Regular Exams Matter for Glaucoma Risk
Using all these tests together gives your eye doctor a complete picture of your glaucoma risk. This is important because glaucoma risk factors are different for everyone and can include family history, age, and diabetes. The American Academy of Ophthalmology recommends a baseline eye exam by age 40, with more frequent exams if you have higher risk factors.
Protect Your Vision With Routine Glaucoma Screening
Glaucoma testing works best as an ongoing process, tracking subtle changes in eye pressure, optic nerve appearance, and peripheral vision over time. The team at EyeHealth Northwest uses this combination of tests to catch glaucoma at its earliest, most treatable stages. If it has been a while since your last comprehensive exam, or glaucoma runs in your family, schedule an appointment at EyeHealth Northwest in Portland, OR, today.
