Glaucoma Testing

You might be surprised at how many tests optometrists and ophthalmologists 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 article describes how your eye care professional assesses your risk and all the tests needed to properly diagnose glaucoma.
 

Risk Factor Assessment

Your optometrist will begin by assessing your risk level for developing glaucoma. This will help determine the frequency and extent of testing needed. Through a family history and medical questionnaire, the eye doctor is looking for the following risk factors:

• Over the age of 60

• Ethnic background such as African or black Caribbean descent

• 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

If you’ve already had a comprehensive eye exam, your optometrist will also consider these risk factors:

• Eye pressure higher than normal (above 21 mm Hg)

• Thin corneas (less than 555 nanometers)
   

Your type of eyesight is also important. People with longsightedness are at a higher risk for narrow-angle glaucoma, a more serious type that can advance quickly. While shortsightedness is associated with open-angle glaucoma, which progresses slowly without any symptoms.
 

Standard Glaucoma Tests

During a comprehensive eye exam, your optometrist 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

Tonometry measures the pressure within your eye. Your optometrist will use a device called a tonometer to measure the pressue within your eye. 

Eye pressure is unique to each person, so it’s not always a reliable indicator for glaucoma. It’s simply another piece of information to help your eye doctor assess your eyes. 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 glaucoma at pressures between 12 -22mm Hg.
 

Ophthalmoscopy

This is an examination of your optic nerve. Your optometrist may use eye drops to dilate the pupil, which makes it possible to see through your eye to examine the shape and color of the optic nerve. Then, using a small device with a light on the end, your optic nerve is magnified. Based on the results of these tests, your optometrist may refer you or ask you to have more glaucoma exams.
 

Supplemental Glaucoma Tests

Perimetry

Perimetry is a visual field test. It creates a map of your complete field of vision. During this test, you’ll look straight ahead and then indicate when a moving light passes your peripheral (or side) vision. Try to relax and respond as accurately as possible. To ensure accuracy, your doctor may repeat the test to see if the results are the same the next time. 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.
 

Fundus Imaging

Digital images will be taken of the retinas which show the optic nerve.  This is repeated at each visit.  Your optometrist is looking for changes to the size and shape of your optic nerve.
 

Pachymetry

Last, your optometrist uses pachymetry as another way to confirm a diagnosis. Pachymetry measures the thickness of your cornea, the clear window at the front of the eye. Pachymetry can help clarify your diagnosis because corneal thickness has the potential to influence eye pressure readings.

Glaucoma diagnosis is not as simple as you might expect. Be sure to have regular eye exams, especially if you have any of the risk factors, to detect glaucoma early.