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Glaucoma causes damage to the optic nerve and is usually associated with high eye pressure – for this reason both the optic nerve and eye pressure needs to be tested to diagnose glaucoma. There are also additional tests that also help to identify the development of glaucoma.

The different tests for Glaucoma

Tonometry

This test is used to measure the pressure inside the eye. There are two types of tonometry:

Non-contact air puff tonometry: This method measures eye pressure without touching the eye, by using a small puff of air. This method is used by most high-street opticians but isn’t very accurate and can overestimate eye pressure.
Goldmann contact tonometry: This method does involve the device touching the eye but numbing eye drops are used to avoid any discomfort. This is the most accurate way to measure eye pressure and is done by trained opticians and all ophthalmologists.

Normal eye pressure ranges from 12mmHg to 24mmHg. Once eye pressure exceeds this, there is a risk of glaucoma developing from the high eye pressure compressing the optic nerve over time.

Ophthalmoscopy / Fundoscopy

Glaucoma causes damage to the optic nerve over time. Ophthalmoscopy, also known as fundoscopy, uses a device called an ophthalmoscope to magnify and shine a light into the eye. The optic nerve is viewed through the pupil to determine if there are any signs of glaucoma – the pupil may be dilated using eye drops to make it easier to see through.

Additional glaucoma tests may need to be performed if eye pressure is outside the normal range or if the optic nerve looks abnormal. These tests include perimetry, gonioscopy, and pachymetry.

Perimetry

A perimetry test is used to map out the patient’s field of vision so that the practitioner can find out whether the patient’s peripheral vision has been affected by glaucoma. During this test the patient looks through a device called a perimeter at a fixed spot in front of them, while lights flash in different areas of their peripheral vision. With this, a map of the patient’s vision is created.

Gonioscopy

Gonioscopy is a test to check whether the drainage angle in the eye is narrow or blocked. The drainage angle allows the excess aqueous humour fluid in the eye to drain as it is produced. If the drainage angle becomes narrow or blocked, the eye pressure builds up and can lead to glaucoma. This test is done by placing a lens with mirrors onto the eye to view the drainage angle.

Pachymetry

This test measures the thickness of the eye’s cornea, which is the clear outer layer of the eye. The test uses a device called a pachymeter which is placed on the front of the eye to determine corneal thickness.