VISION, DEFECTS OF

Abstract

This chapter describes the defects of vision. The act of vision comprises the perception of form, color, and brightness, and the perception of space and distance. These faculties are possessed by all parts of the retina, though in varying degrees, and are of varying importance. The amblyopia of migraine is usually transitory, and may occur either as a central scotoma, hemianopia, or monocular blindness, more rarely as a quadrantic hemianopia or a ring scotoma. The diagnosis is fairly easy, as the amblyopia seldom lasts more than a few minutes, and is followed usually by the characteristic headache and sickness of migraine, sometimes with fortification figures, flashes of light, and other subjective phenomena in the fields of vision. Hysterical amblyopia may, like other hysterical affections, take various forms such as loss of visual acuity, a loss of color vision, or diminution in the visual field. The characteristic form of the visual field in hysteria is either a spiral contraction or an extreme concentric limitation.