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How is Glaucoma Diagnosed? The Most Common Glaucoma Tests

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Older woman having her eye test with her optometrist

Glaucoma can cause significant damage to your eyes. You may not even show any symptoms until your vision is affected, so how do you diagnose this disease? A comprehensive eye exam can determine any problems you may have, and several tests may occur throughout your appointment.

If you have an eye exam soon, learn more about glaucoma diagnosis and the most common glaucoma tests. 

What is Glaucoma? 

Glaucoma is a group of eye conditions causing damage to the optic nerve, with many forms increasing the pressure within your eyes. This condition is one of the leading causes of blindness for older adults, so regular eye examinations are vital for diagnosis. 

Glaucoma typically shows little to no signs until the condition has significantly progressed. You may not even know you have this disease until vision loss occurs. Glaucoma symptoms depend on the type you’re experiencing. Some common forms of glaucoma include:

Primary Open-Angle Glaucoma

Primary open-angle glaucoma is the most common form of glaucoma. The inner eye pressure rises because fluid cannot properly drain, putting pressure on the optic nerve. 

Symptoms of open-angle glaucoma include: 

Angle-Closure Glaucoma 

Angle-closure glaucoma, also known as acute glaucoma, is a less common form of this disease. While the drainage ducts function adequately, the space between the iris and the lens suddenly closes, causing the anterior chamber to fill with fluid. 

The aqueous fluid becomes blocked when the angle narrows, putting pressure on the optic nerve. Acute angle-closure glaucoma is a medical emergency and requires immediate attention. Common symptoms include: 

  • Severe headache 
  • Eye pain
  • Nausea & vomiting 
  • Blurred vision 
  • Eye redness

Normal-Tension Glaucoma

Normal-tension glaucoma does not increase eye pressure, but the optic nerve is still damaged. The drainage ducts work correctly, the space between the iris and the lens is wide enough, but the optic nerve is still affected. Some people are at higher risk of developing normal-tension glaucoma. 

Older man with signs on glaucoma in his left eye.

How is Glaucoma Diagnosed? 

Like many other eye diseases, early detection is crucial for effectively managing glaucoma, but how is it tested? A series of tests in a comprehensive eye exam can help diagnose glaucoma. During your exam, your optometrist may perform several tests to diagnose any problems. 

These tests check 5 glaucoma-related factors

  • The inner eye pressure (tonometry) 
  • The shape and color of the optic nerve (dilated eye exam)
  • The complete field of vision (visual field testing) 
  • The angle in the eye where the iris meets the cornea (gonioscopy) 
  • Thickness of the cornea (pachymetry) 

A thorough eye examination can determine if you have glaucoma or another condition. After diagnosis, your optometrist can recommend a specialized treatment plan for you. Each glaucoma test is different, so you should understand how they work.  

Tonometry 

Tonometry measures your inner eye pressure, known as intraocular pressure (IOP). Your optometrist will use numbing eye drops before this procedure for your comfort. The device then lightly indents your cornea, and the tonometer measures the resistance to this indentation. There are several tonometer variants, including: 

Goldmann applanation tonometer 

The Goldmann applanation tonometer is the most common way to measure IOP. A small sensor attached to an arm presses against your tear film, measuring pressure through a microscope under blue light. 

Tono-Pen handheld electronic contact tonometer

This tonometer runs on batteries, making it completely portable and easy to use. Your optometrist places a sterilized device against your tear film until a pressure reading appears on a digital screen. 

Non-contact tonometer

A puff of air flattens the cornea to measure your internal eye pressure. You do not usually require numbing eye drops for non-contact tonometers. Many clinics use them for screening purposes

Dilated Eye Exam (Ophthalmoscopy) 

A dilated eye exam allows your optometrist to examine your retina. Administered drops dilate your eyes before your eye doctor views the size and shape of the optic nerve. They will examine the retina, optic disc, and blood vessels to identify any issues present.

Visual Field Testing (Perimetry) 

Visual field testing, or perimetry, determines how sensitive your vision is. Your visual field is how wide your eyes can see while focusing on a specific point. This test can help find out if you have any blind spots in your vision. 

For glaucoma, visual field testing can determine if you have suffered any peripheral vision loss. Some common ways to determine your visual field include: 

Gonioscopy 

A gonioscopy exam determines if the angle where the iris and cornea meet is open and wide. Your optometrist administers numbing eye drops before placing a specialized contact lens on the eye. The lens has a mirror to show your optometrist if the angle between the iris and cornea is open and wide or closed and blocked. 

If the angle is closed and blocked, you are more at risk of a sudden or rapid rise in your IOP. In addition to viewing the angle, gonioscopy can find any abnormal blood vessels or damage caused by previous trauma

Pachymetry 

Pachymetry measures the thickness of your cornea. A probe measures your corneal thickness due to its potential to influence your IOP readings. If your optometrist knows your corneal thickness, they can better understand the pressure inside of your eyes. 

Corneal thickness can disrupt an accurate reading of your IOP, causing a misinterpretation of the internal pressure. If your eye doctor does not take your corneal thickness into account, there is potential for misdiagnosis. By measuring the thickness of your cornea and receiving an accurate eye pressure measurement, you can receive an accurate diagnosis. 

The Importance of Early Diagnosis 

An early glaucoma diagnosis can protect your eyes from future complications. Glaucoma causes irreversible damage, but treatments and regular eye examinations can help slow or prevent vision loss. If you have any symptoms of glaucoma or need a comprehensive eye exam, book an appointment with your optometrist. 

Written by Dr. Leslie E. O’Dell

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