You might be surprised at how many tests eye doctors use to diagnose glaucoma. A proper diagnosis requires careful evaluation of many aspects of your eye’s health – from eye pressure to cornea thickness to the health of your optic nerve. This review describes how we can determine your risk and all the tests needed to properly diagnose glaucoma.
We will begin by assessing your risk level for developing glaucoma. This will help determine the frequency and extent of testing needed. By taking a through a family history and medical questionnaire, we are looking for the following risk factors:
Over the age of 60
Ethnic background such as African or black Caribbean descent, Hispanic, or Asian
Family history of glaucoma, such as a sibling or parent with glaucoma
History of eye conditions, injuries or surgeries
Prolonged corticosteroid use (eye drops, pills, inhalers or creams)
Chronic conditions that affect blood flow, such as migraines, diabetes, low blood
pressure or hypertension
Current or former smoker
During your comprehensive eye exam, we will also be looking for these risk factors:
Eye pressure higher than normal (above 21 mm Hg)
Thin corneas (less than 0.5 millimeters)
Larger or asymetric optic nerves
Your type of eyesight is also important. People with farsightedness are at a higher risk for narrow-angle glaucoma, a more serious type that can advance quickly. While nearsightedness is associated with open-angle glaucoma, which progresses slowly without any symptoms.
During your comprehensive eye exam, we will always check for glaucoma, regardless of the risk level. This provides a baseline for comparison as you age. There are two tests: tonometry and ophthalmoscopy.
Tonometry measures the pressure within your eye. There are several ways to check your IOP (intraocular pressure), some requiring numbing drops, others not.
Eye pressure is unique to each person, so it’s not always a reliable indicator for glaucoma. It’s simply another piece of information needed to determine if glaucoma is present. The range for normal pressure is 12-22 mm Hg (“mm Hg” in millimeters of mercury, a scale for recording eye pressure). Most glaucoma cases are diagnosed with pressure over 20mm Hg. However, some people can have Low Tension Glaucoma with pressures as low as 12.
This is an examination of your optic nerve. We utilize the latest retinal imaging to assess the shape and color of the optic nerve. We can also use a special lens that will allow us to directly view the optic nerve. Based on the results of these tests, we may advise additional glaucoma testing.
This test creates a map of your complete field of vision. During this test, you’ll fixate on a taget straight ahead and then indicate when you see a light shining in your peripheral vision. This test can be challenging form some patients. To ensure accuracy, we might want the test perfomed aagain to see if the results can be repeated. If you’ve been diagnosed with glaucoma, a visual field test is usually recommended at least once per year to assess changes to your vision.
OCT is advanced technology that can examine the thickness of the nerve layer UNDERNEATH the optic nerve, not able to be seen on any other test. Glaucoma causes a thinning of the optic nerve fibers. This test gives us the ability to diagnose glaucoma as much as five years earlier that previously possible. It is quick, painless, and non invasive. We advise everyone to get a baseline OCT. If you have glaucoma, or are considered high risk of developing glaucoma, this test needs to be done annually.
This diagnostic exam helps determine the angle of your iris and cornea. First, you’ll receive eye drops to numb the eye. A hand-held contact lens is gently placed on the eye. A mirror on the contact lens lets us see if the angle is closed and blocked (a possible sign of angle-closure or acute glaucoma) or wide and open (a possible sign of open-angle, chronic glaucoma).
Lastly, we may need pachymetry as an additional piece of information to accurately confirm a diagnosis. Pachymetry measures the thickness of your cornea, the clear dome over thbe front of the eye. A probe called a pachymeter is gently placed on your cornea to measure its thickness. Pachymetry can help confirm the diagnosis of glaucoma as thinner corneas are more prone to be associated with glaucoma and can give falsely lower IOP measurements.
As you can see, a glaucoma diagnosis is not as simple as just checking the eye pressure. Regular eye exams are needed, especially if you have any of the risk factors, to detect glaucoma early.