Visual fields

Glaucoma damages vision, but the vision that is lost at first is usually in the peripheral part of the vision. Usually this visual loss is not noticeable. However, detecting this vision loss aids in the diagnosis of glaucoma. Moreover, if the loss worsens it is a sign that the treatment for the glaucoma is inadequate. For that reason it is important to measure the peripheral vision and to repeat the measurements frequently.

The measurement of the peripheral vision is called Visual Field Testing. There are many ways to do this, but all boil down to the same thing. The patient is exposed to dimmer or smaller lights at various areas in the peripheral vision until the smallest light that can be seen at each spot is determined.

People can have glaucoma without any measurable visual field loss, but when visual field loss is detected this is an important in determining not only that glaucoma is present, but how much damage it has done. If areas of visual loss worsen on later exams, or new areas of loss are detected it is evidence that the pressure needs to be further lowered.