Scotoma Health Dictionary

When the eye looks at a speci?c point or object, that point is seen clearly. Other objects within a large area away from this ?xation point can also be seen, but less clearly. The area that can be seen around the ?xation point, without moving the eye, is known as the ?eld of vision. The extent of the ?eld is limited inwards by the nose, above by the brow and below by the cheek. The visual ?eld thus has its greatest extent outwards from the side of the head. The ?eld of vision of each eye overlaps to a large extent so that objects in the centre and towards the inner part of each ?eld are viewed by both eyes together. Because the eyes are set slightly apart, each eye sees objects in this overlapping part of the ?eld slightly di?erently. It is because of this slight di?erence that objects can be perceived as three-dimensional.

Defects in the visual ?eld (scotomas) can be produced by a variety of disorders. Certain of these produce speci?c ?eld defects. For example, GLAUCOMA, some types of brain damage and some TOXINS can produce speci?c defects in the visual ?eld. This type of ?eld defect may be very useful in diagnosing a particular disorder. The blind spot is that part of the visual ?eld corresponding to the optic disc. There are no rods nor cones on the optic disc and therefore no light perception from this area. The blind spot can be found temporal (i.e. on the outer side) of the ?xation point. (See also EYE.)... vision, field of

n. the forewarning of an epileptic or migrainous attack. An epileptic aura (sometimes known as the preictal phase, because it precedes the main *ictus or seizure) may take many forms, such as an odd smell or taste. The migrainous aura may affect the patient’s eyesight with visual phenomena, such as fortification spectra (zigzag lines) or scotomas (black holes in the visual field), but it may also result in pins and needles, weakness of the limbs, or *aphasia.... aura

1. a sickle-shaped *scotoma appearing as an upward or downward extension of the blind spot. 2. a test to confirm leakage of the aqueous humour. *Fluorescein sodium dye is instilled and viewed with cobalt blue light; a bright green flow of liquid is seen at the site of the leakage. [E. Seidel (1882–1948), German ophthalmologist]... seidel sign

n. shimmering coloured lights, accompanied by blank spots in the visual field (transient scotomata), often seen by sufferers at the beginning of an attack of migraine.... teichopsia