A glaucoma eye exam checks your eye pressure, corneal thickness, drainage angle, optic nerve, and side vision. No single test can diagnose glaucoma, so doctors use several together. This matters because early glaucoma usually has no symptoms, and the National Eye Institute (NEI) reports that half of people with glaucoma do not know they have it.
Glaucoma damages the optic nerve, the cable that carries vision to the brain. The damage is permanent, so finding it early is the goal of every glaucoma test.
Why Early Glaucoma Has No Warning Signs
People often expect the "signs of glaucoma" to be pain or blurry vision. The most common type, open-angle glaucoma, usually causes neither. A large review in JAMA notes that glaucoma progresses without symptoms until the disease is advanced. See our glaucoma symptoms page.
The Tests, One by One
1. Tonometry: measuring eye pressure
Tonometry measures intraocular pressure (IOP), the fluid pressure inside your eye, in millimeters of mercury (mm Hg). After numbing drops, the doctor gently touches the eye with a small probe, or a device uses a puff of air.
What is a normal eye pressure reading? The Glaucoma Research Foundation states that normal eye pressure averages from 10 to 21 mm Hg.
Why a normal number does not rule out glaucoma. According to the JAMA review, several population-based studies found eye pressure below 22 mm Hg in 25% to 50% of people with glaucoma. At the same time, many people with high pressure never develop glaucoma. Pressure is a risk factor, not a diagnosis. Read why a normal eye pressure reading can miss glaucoma and our page on normal-tension glaucoma.
2. Pachymetry: measuring corneal thickness
Pachymetry measures the thickness of the cornea, the clear front window of the eye, in a few seconds.
Corneal thickness matters for two reasons. First, it can affect how accurate the pressure reading is. Second, the Ocular Hypertension Treatment Study (OHTS), a major trial of people with high eye pressure, found that a thinner central cornea was a powerful predictor of who went on to develop glaucoma. Older age, a larger optic nerve cup, and higher pressure also predicted glaucoma in that study.
3. Gonioscopy: looking at the drainage angle
Your eye drains fluid through the drainage angle, where the iris (the colored part) meets the cornea. After numbing drops, a small mirrored lens rests on the eye so the doctor can see whether the angle is open, narrow, or closed. That helps decide which type of glaucoma you may have. See our narrow-angle glaucoma page for more on narrow angles.
4. Dilated optic nerve exam: the cup-to-disc ratio
The doctor looks at the optic nerve at the back of the eye, usually after dilating drops widen the pupil. The JAMA review calls changes in the optic nerve and nerve fiber layer the most important part of a glaucoma diagnosis.
Cup-to-disc ratio explained. The optic nerve head (the disc) looks like a round circle. In its center is a pale dip called the cup. The cup-to-disc ratio compares the width of the cup to the width of the whole disc. As glaucoma kills nerve fibers, the rim of healthy tissue thins and the cup gets larger.
A larger cup does not always mean glaucoma. Healthy optic nerves vary widely in appearance, and some people are simply born with large cups. What matters most is the rim's shape, differences between the two eyes, and whether the cup grows over time.
5. OCT: a scan of the nerve fiber layer
Optical coherence tomography (OCT) is a painless, no-touch scan that takes a detailed cross-section picture of the optic nerve and the retinal nerve fiber layer, the thin layer of nerve fibers that glaucoma damages.
The Glaucoma Research Foundation describes OCT as the most commonly used laser-based imaging method for the optic nerve. The JAMA review notes that imaging like OCT has improved the identification of early disease and of change over time.
6. Visual field test: checking side vision
Visual field testing (perimetry) maps your side vision. You look at a center light and press a button each time you see a faint flash elsewhere.
Many patients find this test tiring. The lights are meant to be hard to see, so you will miss some, and that is expected. Read why visual field tests are hard and why they still matter.
Why do it if OCT exists? The two tests answer different questions. OCT shows structure. The field test shows how well you actually see. The JAMA review notes that 30% to 50% of retinal ganglion cells (the nerve cells glaucoma damages) may be lost before standard field testing detects a defect, which is why doctors use both.
How Long Does a Glaucoma Eye Exam Take?
Plan on a longer visit than a routine eye exam for your first glaucoma visit. Waiting for dilating drops to work and doing the visual field test take the most time. Follow-up visits are often shorter.
Bring a list of your medicines and any past eye records.
Will My Eyes Be Dilated? Can I Drive?
Most first glaucoma exams include dilation so the doctor can see the optic nerve clearly. Dilated eyes are light sensitive and may blur up close for several hours.
Many people prefer to bring a driver. Bring sunglasses. If you have been told you have narrow angles, let the staff know before any drops are placed.
How Often Should You Be Checked for Glaucoma?
The American Academy of Ophthalmology (AAO) Comprehensive Adult Medical Eye Evaluation Preferred Practice Pattern recommends this schedule for adults with no symptoms and no risk factors:
| Age | How often |
|---|---|
| Under 40 | Every 5 to 10 years |
| 40 to 54 | Every 2 to 4 years |
| 55 to 64 | Every 1 to 3 years |
| 65 and older | Every 1 to 2 years |
For adults with risk factors, the same guideline recommends more frequent exams. The AAO clinical statement on frequency of ocular examinations gives these intervals for people at higher risk, such as African American and Hispanic individuals at higher risk of glaucoma:
| Age | How often |
|---|---|
| Under 40 | Every 2 to 4 years |
| 40 to 54 | Every 1 to 3 years |
| 55 to 64 | Every 1 to 2 years |
For people 65 and older at higher risk, the AAO statement says the timing should be based on each person's particular risks. If you already have glaucoma or are a glaucoma suspect, your specialist will set a closer schedule.
Common glaucoma risk factors include older age, a family history of glaucoma, African American or Hispanic/Latino ancestry, high eye pressure, and use of steroid medicines. Try our glaucoma risk calculator to see where you stand, then bring the result to your visit.
From the Glaucoma Specialists
Do not let one normal pressure reading reassure you, or one high reading scare you. Glaucoma is diagnosed by putting all the tests together and watching for change over time. Keep your follow-up visits, even when your eyes feel perfect, and if a parent, brother, or sister has glaucoma, get checked yourself.
Glaucoma Testing in Upland and the Inland Empire
Inland Glaucoma Center in Upland, California, is an independent practice, not a corporate chain. It is led by Robert Gunzenhauser, MD, a Harvard-educated, UCLA fellowship-trained glaucoma specialist, and Marc Shomer, MD, PhD, Adjunct Associate Professor of Ophthalmology at the Keck School of Medicine of USC. Both are board certified.
We see patients from Upland, Rancho Cucamonga, Ontario, Claremont, Montclair, Pomona, Fontana, Chino, Riverside, and San Bernardino. Learn more about glaucoma screening and diagnosis at our office.
Call 909-315-6891 or request an appointment.
Works Cited
- Weinreb RN, Aung T, Medeiros FA. The pathophysiology and treatment of glaucoma: a review. JAMA. 2014;311(18):1901-1911. https://doi.org/10.1001/jama.2014.3192 (PMID 24825645)
- Gordon MO, Beiser JA, Brandt JD, et al. The Ocular Hypertension Treatment Study: baseline factors that predict the onset of primary open-angle glaucoma. Arch Ophthalmol. 2002;120(6):714-720. https://doi.org/10.1001/archopht.120.6.714 (PMID 12049575)
- Chuck RS, Dunn SP, Flaxel CJ, et al. Comprehensive Adult Medical Eye Evaluation Preferred Practice Pattern. Ophthalmology. 2021;128(1):P1-P29. https://doi.org/10.1016/j.ophtha.2020.10.024 (PMID 34933742; recommendations read at https://aao.org/preferred-practice-pattern/comprehensive-adult-medical-eye-evaluation-ppp)
- American Academy of Ophthalmology. Frequency of Ocular Examinations. Clinical statement, revised February 2015. https://www.aao.org/clinical-statement/frequency-of-ocular-examinations (accessed October 2026)
- Glaucoma Research Foundation. Glaucoma Test: What To Expect (Testing for Glaucoma). https://glaucoma.org/five-common-glaucoma-tests/ (accessed October 2026)
- Glaucoma Research Foundation. What Is Considered Normal Eye Pressure Range? (IOP). https://glaucoma.org/?p=6293 (accessed October 2026)
- National Eye Institute. Glaucoma. https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/glaucoma (accessed October 2026)