Perimetry (Visual Field Test)

A test that maps your side vision to detect blind spots, used mainly to diagnose and monitor glaucoma.

Perimetry maps the full extent of what you can see while looking straight ahead, including your side (peripheral) vision. It finds blind spots that you may not be aware of, because the brain is very good at filling in the gaps.

Why it matters in glaucoma

Glaucoma usually affects side vision first, while central vision stays clear until late. Visual field testing helps confirm the diagnosis, and repeat tests over time help show whether the condition is stable or progressing.

Other uses

Your doctor may also use perimetry when investigating certain conditions of the retina, the optic nerve or the visual pathways.

Who is this for?

A visual field test may be advised if you:

• Have glaucoma or are suspected of having it.
• Have high eye pressure or an optic nerve that looks suspicious.
• Have noticed patches of missing vision.
• Have certain optic nerve or neurological conditions.

What the procedure involves

1. You sit at the machine with one eye covered and your glasses power set as needed.
2. You look at a central target throughout the test.
3. Small lights appear in different places, and you press a button each time you see one.
4. Each eye is tested in turn, and the results are mapped for your doctor.

Recovery and follow-up

There is no recovery time. Come rested, wear or bring your glasses and take your time. It is normal to miss some lights, and it is normal for early tests to need repeating, since results improve with practice.

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