What to Expect During Glaucoma Screening and How to Interpret Results

Glaucoma is often picked up during a routine comprehensive eye exam, but some people are at higher risk for glaucoma than others. These patients are recommended to have a screening appointment or may be offered one if they get in touch with their eye doctor describing symptoms of glaucoma.

​​​​​​​Here’s what you need to know about what to expect during glaucoma screening and what the results mean.

What is involved in glaucoma screening and what do the results of each test mean?

Glaucoma screening is a very simple and straightforward process that is usually completely painless for patients. There are several different elements involved in the screening. These include:

​​​​​​​Eye pressure test

This is often performed with an instrument called a tonometer which is used to measure the pressure inside the eye. You’ll have a small amount of anesthetic medicine administered to your eye before they then gently touch the tonometer to it which will give them a pressure reading. Alternatively, a different tool that releases a puff of air into the eye but doesn’t touch it may be used. At no point will you experience any pain.


The normal range for intraocular pressure is around 10-20 mmHg. Around 90% of patients will experience intraocular pressure – or IOP – within this range. However, this doesn’t mean that pressure above this is automatically a sign of glaucoma. Instead, your eye doctor will take other test results into account to determine whether a diagnosis is necessary. In some instances, our eye doctor may monitor your IOP over a number of years to see if the pressure is gradually increasing. ​​​​​​​


This element of glaucoma screening is an examination of the front part of the eye and assess the fluid-filled space between the iris and the cornea. This part of the eye is where the fluid should drain out from, and a gonioscopy can evaluate whether the area is open and draining properly, or blocked. The results of this test can help your eye doctor to determine the type of glaucoma that you have. Open-angle glaucoma (where there is no visible problem with drainage) is the most common, affecting around 90% of patients. However, closed-angle glaucoma is much more serious since it can lead to sudden and permanent vision loss.

Visual field test

Although glaucoma rarely presents with any noticeable symptoms before it is diagnosed, a loss of peripheral vision is one effect that patients may notice. A visual field test, also known as perimetry testing, is an assessment of your field of vision. The process involves showing you a series of dots and asking you to press a button to indicate which you can see.

Evaluating the results of a visual field test is simple. If you can’t see spots in the periphery, your vision may have been damaged by glaucoma.

Slit lamp exam / optical coherence tomography

A slit lamp is a piece of equipment that looks like a microscope with a bright light. Optical coherence tomography is a special type of scan that uses rays of light to scan the back of your eye and create an image of it. Both of these tests are used to visualize and assess your optic nerve, which is the nerve that connects each eye to the brain. Abnormalities with its appearance can indicate several different eye conditions including glaucoma.

Our eye doctor will look at the results of each of these elements of your screening appointment to determine if a glaucoma diagnosis is appropriate and to decide what the next steps in your care should be. The results can inform which treatments you are offered, how quickly they are offered, and in what order.

If you are concerned about glaucoma, or to schedule a glaucoma screening appointment, please call our dedicated eyecare team 718-565-2020. ​​​​​​​