Glaucoma

What is a visual field test like?

A visual field test maps how sensitive your vision is across the whole field of view. You look steadily at a central target inside a bowl shaped screen and press a button whenever you notice a faint light. Each eye takes roughly five to ten minutes. It is painless, and it shows function that scans cannot measure.

How it works

The machine shows lights of different brightness at many points, adjusting them according to your responses to find the dimmest light you can detect at each spot. The result is a map where healthy areas appear pale and areas of reduced sensitivity appear grey or black.

Glaucoma typically produces an arc shaped defect above or below the centre, or a step at the nasal side, long before the centre is involved.

Getting a reliable result

  • Wear the lens the technician gives you, and keep your forehead against the rest
  • Keep looking at the central target, not at the lights, and press whenever you think you see one
  • Expect many lights to be very faint. Missing some is normal and does not mean failure
  • Say if you need a pause, especially in the second eye
  • First tests are often less accurate because the task is unfamiliar, so a repeat is common and not a cause for worry

How results are used

Your ophthalmologist reads the pattern, the reliability indices and, most importantly, the comparison with your previous fields. A stable series supports current treatment. A worsening series suggests that pressure control needs to be stronger, even when you feel no different.

Frequently asked questions

Can a bad field test result be wrong?
Yes. Tiredness, drooping eyelids, an uncorrected prescription or unfamiliarity with the test can all mimic loss. Suspicious results are normally repeated before conclusions are drawn.
Does the test need drops?
No, the field test itself does not. Drops may be used for other parts of the same appointment.

Concerned about these symptoms?

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