A scotoma is an area of diminished vision within the visual field or degenerated visual acuity which is surrounded by a field of normal vision. Scotomas may be central, if caused by a disease which affects the macula or optic nerve, or peripheral if the result of chorioretinal lesions or retinal holes.
A scotoma may be caused by a wide range of disease processes, affecting either the retina (in particular its most sensitive portion, the macula) or the optic nerve itself. A pathological scotoma may involve any part of the visual field and may be of any shape or size. A scotoma may include and enlarge the normal blind spot. Even a small scotoma that happens to affect central or macular vision will produce a severe visual handicap, whereas a large scotoma in the more peripheral part of a visual field may go unnoticed by the bearer because of the normal reduced optical resolution in the peripheral visual field.