Color-b/indecss is noticed under its own name.
Aright.blindncss, or beincralopia (from the Greek, signifying `day-sight'), is a peculiar form of intermittent blindness. the subjects of which see perfectly with an ordinary light, but become entirely and almost instantaneously blind as soon as twilight commences. It is seldom encountered in this country except among sailors just re turned from tropical regions. It is frequent among the natives of sonic parts of India, who it, as sailors do, to sleeping exposed to the moonlight. The mutt probable cause of the affection is, however, exhaustion of the power of the retina from the over-excitement of excessive light, so that this organ is rendered incapable of appreciating the weaker stimulating action of twilight or moonlight.
Snow-b/iminess must be regarded as an allied affection to the preceding.
Day-blindness, or nyclalopia, refers to the con dition in which the sight is better in a feeble light, as at dusk, than in bright light. This oc curs in amblyopia (q.v.) from the abuse of to bacco, and in cases in which there is defective vision of the central portion of the visual field.
For example: if there is an opacity of the central portion of the lens or cornea, the dilatation of the pupil which takes place in a feeble light al lows the person to see through the unobstructed portion of the cornea or lens surrounding the opacity.
Colored vision sometimes occurs either with or without retinal changes. Red vision. orythropsia, occurs after extraction of a cataract. Xanthopsia, or yellow vision, may follow the ingestion of san tonin, gelsemium, chromic and picric acids, and amyl Cannabis lndiea some times causes violet vision. Red or blue vision may result from the use of iodoform, and cocaine has caused colored vision. Phosphorus is said to cause sparks and flashes of light, and the same is said to be caused at times by. belladonna and santonin.
Other defects of sight are described under the headings AMAURosIs AMBINOPIA ; ASTIGMA TISM; HEMIOPIA ; HETEROPIIORIA. See VISION.