Question: What is perimetry, and how is it used to diagnose glaucoma?
Answer: Perimetry refers to the technique of quantitating, or measuring, the visual field. The visual field refers to the part of vision that is not the very center part of your vision -- that is often measured by when we ask you to read the eye chart. But beyond what you see on the eye chart, there's the whole rest of your vision, your peripheral vision. Perimetry refers to the technique of measuring that visual field.
Glaucoma tends to affect the peripheral visual field first, so it's very important that we measure and examine it. It's not only used for the diagnosis, but it's also used regularly to see if the disease is progressing. If there is any change in the visual field, then you'd want to intervene to see if there's something different you can do to halt the disease progress.