Understanding Glaucoma Test Results: What do They Mean?

Glaucoma  | 

One of the leading causes of blindness is a condition with no noticeable symptoms, which makes regular exams and tests absolutely vital. Glaucoma has little to no early symptoms, it progresses gradually and can cause irreversible damage to the optic nerve that could lead to vision loss.

Anyone over the age of 60, who is of African descent and over 40, or has a family history of glaucoma may be at increased risk for the condition.

How often should you be tested? In general, if you are over 40 and have a family history of the disease, WebMD says an eye exam every one or two years is recommended. If you have glaucoma in your family or a condition that could contribute to the disease, such as diabetes, you may need to go more often.  

This article explores tests, how to tell if you have abnormal glaucoma test results and what they mean for you.

OCT Test

Optical coherence tomography (OCT) is an extremely valuable test for glaucoma. This non-invasive imaging test uses light waves to take cross-section pictures of the retina. Ophthalmologists and Optometrists use these images to map and measure the thickness of the retina’s distinctive layers. Compared with visual field testing, optic nerve imaging such as OCT provides more objective, quantitative information for diagnosing early-to-moderate glaucoma. These images also provide an accurate baseline which can help your eye doctor track changes to your retina over time.

In addition to glaucoma, OCT is useful in diagnosing other eye conditions such as diabetic retinopathy and age-related macular degeneration (AMD).

Visual Field Test

Because glaucoma can cause peripheral vision loss, a visual field test may be done to measure your peripheral vision.

There are various ways to perform a field vision test, but we usually test one eye at a time using a specialized instrument. The test begins when you’re seated in front a machine, looking into it and asked to focus on the light ahead. During the test, a faint light will appear momentarily at different positions in your field of vision. You will be asked to press a button each time you detect the light.

Your eye doctor can use your first glaucoma test results as a baseline and then use future results to compare to the initial test results to determine disease progression.

Ask your eye doctor to explain your exam so you understand glaucoma test results and whether you’re experiencing peripheral eyesight loss.


This test is often performed during regular eye exams to test the pressure within the eyeball. The Glaucoma Research Foundation describes the test as requiring eye drops that anesthetize the eye, while a small device is pressed on the eyeball or a small puff of air is expelled to test the eye pressure.

The Glaucoma Research Foundation says that the range normal pressure is 12 – 22 mm Hg; an individual is usually diagnosed as “glaucoma suspect” when the pressure exceeds 22 mm Hg. Because glaucoma is a complex condition, intraocular pressure (IOP) is only one glaucoma test result that an eye doctor will consider when deciding on a final diagnosis.


Eye drops are used to dilate the pupil and your doctor will look into the eye to visually examine the optic nerve. A device with a light magnifies the nerve. If the optic nerve’s shape or color don’t look normal, or the pressure within the eye is higher than the normal range, you doctor may perform more exams to double-check the abnormal glaucoma test results and be certain of the diagnosis.


This test can help determine if the patient has open angle or angle-closure glaucoma. This exam begins with numbing eye drops, after which hand-held, mirrored contact lenses are placed carefully on the eye. The eye doctor can see the angle of the iris and cornea by using the mirror in the contact, and detect whether it’s blocked, which could be angle-closure glaucoma, or open, which could indicate open-angle glaucoma.  


This test measures the thickness of the cornea with a probe called a pachymeter, which is placed on the front of the eye. Corneal thickness can impact eye pressure readings – thicker corneas can overestimate IOP, while a thin eye covering can underestimate IOP. A thinner cornea can be dangerous because it can mask a high IOP.

Understanding glaucoma test results

As indicated above, if your glaucoma test results indicate elevated IOP, you are likely a “glaucoma suspect,” but to arrive at a diagnosis of glaucoma, you must see an eye doctor. Even with a high IOP, if you have a thick cornea, the measurement could be artificially high.

The best option to manage glaucoma and overall eye health is to have an annual exam and work with an eye doctor who can map out the changes in your vision over time. When your eye doctor makes a diagnosis, the results of each test will be taken into consideration to determine whether you have glaucoma, the stage of your condition and if the condition is progressing.

If you are currently looking for a qualified eye doctor or would like to learn more about glaucoma testing and treatment options, the doctors at Barnet Dulaney Perkins are happy to help. Contact us or request an appointment online today.


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