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Diagnosis of Glaucoma

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The only way of diagnosing glaucoma is by means of a complete eye examination. Thus, apart from measuring the intraocular pressure, the ophthalmologist will examine the patient’s filtration angle, optic nerve and peripheral vision.

Tests used to diagnose Glaucoma

Slit-lamp examination. The patient sits on a chair and places their chin and forehead in front of a special high-magnification microscope used to examine all the structures in the eye.

Tonometry. The ophthalmologist instils a drop of dye with anaesthetic into the patient’s eye and uses a slip-lamp with a special, built-in device (a cone that produces blue light) to painlessly measure the intraocular pressure.

Gonioscopy. After anaesthetising the eye, a special lens with mirrors is used to study the eye’s drainage filter without causing the patient any pain.

Optic nerve examination. A special magnifying glass is placed in front of the light from the lamp and used to look at the fundus of the eye and inspect the optic nerve.

Pachymetry. The optometrist uses a probe connected to a computer to measure the thickness of the cornea.

Optical coherence tomography. This technique uses a computer to take high-resolution photographs, so the ophthalmologist can visualise and check the thickness of the layers of the optic nerve fibres.

Campimetry. Using a device equipped with a button and under the optometrist’s supervision, the patient indicates when they notice lights that appear at the sides of their vision but while always looking at the reference light in the middle. This technique is used to study the patient’s peripheral vision.

Campimetry

Campimetry is one of the most important tests in the diagnosis and monitoring of glaucoma as it is the only technique that is suitable for studying the patient’s peripheral vision, in other words, the type of vision that is affected by glaucoma.

The patient uses a button to indicate when they notice white lights that appear at the sides of their vision but while always looking at the orange reference light shining in the centre. One eye is covered first (usually the left eye) and the test is performed with the other (the right eye), then the same procedure is completed with the other eye. The test is carried out under the supervision of an optometrist.

It has been shown that the test gives more reliable results when the patient is relaxed, so it is important to explain beforehand how the test works in order to obtain the best results.

The test comprises the following steps:

The patient should fix their gaze on the orange reference point at all times and try to notice when the white lights appear in the corner of their eye. If they try to find the white lights by looking at them directly, the test will not assess their peripheral vision correctly.
They should be comfortable, so it is important to position their head, chin and back correctly. If not, the patient should tell the technician performing the test.
If they feel uncomfortable at any time, the patient can ask for the test to be paused and continued when they feel better.
They must indicate when they notice any white lights at the side of their vision, regardless of how bright they are. There will be periods when they do not need to press the button because there are no lights. The test tries to determine the patient’s limit (threshold), that is, it gets increasingly difficult to see the light until it becomes impossible. Therefore, there is always a point when the patient, even those who do not have glaucoma, feels like they are failing the test.
It is normal for the patient to miss some lights. The test has a fail-safe system, so any lights that go unnoticed are repeated more than once.
The test is individual to each patient; it adapts to their speed and vision at the time and therefore no two tests are the same.

Substantiated information by:

Elena Fraga Pumar Optometrist Ophthalmology Department

Elena Milla Griñó Ophthalmologist Ophthalmology Department

Marta Pazos López Ophthalmologist Ophthalmology Department

Published: 19 October 2018
Updated: 19 October 2018

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