[Scotomas: assessment by the patient and by the physician. There's nothing to see]

Contrary to long-held beliefs, plasticity occurs in the adult cerebral cortex, and allows the brain to adapt to background modifications or to damage of the nervous system. Cortical changes occurring following focal visual deafferentation modify visual perception, by filling in visual field defects with information from the area surrounding the scotoma. This causes affected subjects to ignore or underestimate their defects. With visual field defects, cortical plasticity also causes distortion in spatial perception. In ophthalmological daily practice, the effects of cortical plasticity are prominent, but are usually unrecognized. They result in unawareness of field defects following retinal photocoagulation, and cause delay in recognizing visual field defects, they e.g., in early stages of simple chronic glaucoma. In addition affect the results of some procedures for testing the visual field, and increase patients' difficulty in coping with activities in everyday life. It is important to introduce into clinical practice the concept of dissociation between actual and perceived defects in the visual field, resulting from the filling-in process. It can be demonstrated using a "double Amsler grid test".