6 Tests for Diagnosing Glaucoma

Vision loss from glaucoma may be prevented if diagnosed early

A complete eye exam includes a check for glaucoma. Glaucoma is an eye disease usually caused by elevated pressure in the eye. Glaucoma can cause vision loss, often without any warning signs or symptoms.

Regular eye exams, including specific glaucoma tests, are important for the early detection of glaucoma. If diagnosed early enough, glaucoma can be properly managed to prevent major loss of vision.

This article reviews six tests used to help detect glaucoma. You'll learn about the individual glaucoma tests, including who needs these tests, what to expect, and how to interpret results.



Intraocular pressure testing for glaucoma

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Tonometry is a very common glaucoma test to measure the pressure inside the eye, or intraocular pressure (IOP).

Having eye pressure higher than normal puts you at higher risk for glaucoma. But it's not a definite diagnosis of glaucoma.

Most people fall into a normal range, but it's possible to have glaucoma with lower eye pressure, and not to have glaucoma with higher pressures.

An important measure is whether the pressure fluctuates up and down a lot, and what that particular eye pressure is doing to your eye.



Ophthalmoscopy is used to examine the inside of the eye.

What to Expect

An ophthalmoscopy can be performed on a dilated or undilated eye. An eye doctor uses special magnifying lenses and medical devices to view the optic nerve.

The color, shape, and overall health of the optic nerve is important in glaucoma assessment.

The doctor may also use a digital camera to photograph the optic nerve. Sometimes, stereo photographs are taken to give a 3-dimensional picture to better assess the overall shape of the optic nerve.



Gonioscopy is a glaucoma test that uses a special mirrored device to gently touch the surface of the eye.

Gonioscopy examines the angle where the cornea meets the iris. Whether this angle is open or closed can tell the doctor what type of glaucoma is present, and how severe glaucoma may be.

Gonioscopy can also be completed using optical coherence tomography.


Visual Field Test

A visual field test, or perimetry, is a test that measures how sensitive a person's vision is.

What to Expect

During a visual field test:

  • You will look straight ahead at a small light or another target.
  • The examiner will ask you to let them know when you see a light flash off to the side in your peripheral vision.

Most visual field testing today is computerized. Visual field testing usually needs to be repeated several times before the doctor can make a valid assessment.


Nerve Fiber Analysis

Nerve fiber analysis is a newer glaucoma test that measures the thickness of the nerve fiber layer. Thinner areas may indicate damage caused by glaucoma.

Who Needs This Test?

Nerve fiber analysis is especially good for patients who have clinical features or risk factors that increase the chance of developing glaucoma.

It can also indicate if a person’s glaucoma is progressively becoming worse.



Pachymetry is a method that measures the thickness of the cornea. Although research is still being conducted on the importance of corneal thickness, pachymetry is starting to play a larger role in glaucoma testing.

The thickness of the cornea seems to influence the eye pressure reading when tonometry is performed.

2 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Lee SY, Bae HW, Kwon HJ, Seong GJ, Kim CY. Utility of Goldmann applanation tonometry for monitoring intraocular pressure in glaucoma patients with a history of laser refractive surgery [published correction appears in PLoS One. 2018 Oct 25;13(10):e0206564]. PLoS One. 2018;13(2):e0192344. Published 2018 Feb 5. doi:10.1371/journal.pone.0192344

  2. Ahmad SS. Glaucoma suspects: a practical approachTaiwan J Ophthalmol. 2018;8(2):74–81. doi:10.4103/tjo.tjo_106_17

By Troy Bedinghaus, OD
Troy L. Bedinghaus, OD, board-certified optometric physician, owns Lakewood Family Eye Care in Florida. He is an active member of the American Optometric Association.