How Optometrists Screen for Glaucoma

Glaucoma is defined as a degeneration of the optic nerve and impaired eyesight because of pressure within the eye.  It is a serious eye disease that has no cure. The effects of glaucoma can be slight vision loss to total blindness. Medication or surgery can slow the loss of vision, however, about 10% of people who are diagnosed with glaucoma and get treatment still lose their eyesight.  A proper diagnosis is the first step in preserving vision. While an online vision test might be able to detect certain eye conditions, it is best to see an optometrist for proper diagnosis of glaucoma.  

Often times, no symptoms are present with glaucoma as there is no pain with increased eye pressure.  An estimated 3 million Americans have the condition but only about half realize they have it.  Early detection is imperative in order to start treatment immediately.  An eye exam with a vision screener performed by an optometrist will include five common tests for screening for glaucoma.


In this test, the optometrist will look at inner eye pressure.  Eye drops are used to numb the eye and the doctor uses a tonometer to measure the patient’s inner pressure in the eye.  A small amount of pressure is applied to the eye. The normal range is 12-22 mm HG (millimeters of mercury).  


The shape and color of the optic nerve are also examined for signs of glaucoma.  Eye drops are used to dilate the eye so the optometrist can see through the eye to see the optic nerve more clearly.  If the optic nerve does not look normal or is damaged, the optometrist may ask the patient to have another glaucoma exam.


The patient’s complete field of vision is tested.  This helps to determine if a patient’s vision has been compromised by glaucoma.  The doctor will ask the patient to indicate by pressing a button when a moving light passes through their peripheral vision.  The test documents central and side vision.  


This test measures the angle in the eye where the iris meets the cornea.   A contact lens is placed on the patient’s eye. It has a mirror that shows the optometrist if the angle between the iris and cornea is closed and blocked or wide and open.  Either extreme can be an indication of glaucoma.  


The thickness of the cornea is measured in this part of the eye exam.  A probe called a pachymeter is placed on the front of the eye to measure the cornea’s thickness.  This measurement can determine the severity of glaucoma and can assist in coming up with a treatment plan.  

Since glaucoma can be difficult to diagnose, more than one test is often needed to determine a treatment plan.  Eye doctors look at many factors before deciding which treatment is best. Many times, glaucoma can be controlled with eyedrop medicine to help lower eye pressure, especially if it is diagnosed early on via a vision screener.