What types of visual field defects occur in different eye and brain disorders?
To understand the types of visual field defects that occur one must know a little something about the projection of visual space on the pathway. Visual space is mapped in characteristic patterns at different levels of the visual pathway. This means that a specific visual field defect can reflect disease or damage to specific portion of the visual pathway. The visual fields of the right and left eyes are separately projected; so that a disease of one eye only causes a field defect in that eye only. In some genetic conditions, such as congenital retinal degeneration however, the visual fields of both eyes are affected similarly. Visual field defects affecting the optic nerves and chiasm may produce very different field defects in right and left eyes. At the optic chiasm, about half the optic fibers from each eye project to the right and left cerebral hemispheres in a strictly topographic pattern. The fibers from the nasal half of the retina (temporal field of that eye) cross to the oppos
