What can defects mean?

Defects in the visual field can be caused by a wide variety of diseases of the eye and brain (for example, glaucoma, cataract, stroke, tumour, etc). Not all ocular and brain disorders
cause visual field defects. Conversely, not all visual field abnormalities indicate significant disease. For example, some defects are caused by harmless retinal scars. As with other methods of testing the visual field, genuine defects can sometimes be missed, especially if mild. Furthermore, abnormal results can occur without significant defects being present, especially if the test is not performed correctly (for example, without proper spectacles).

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