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Medical Definition of Night myopia
1. In dark adaptation the eye becomes more sensitive to shorter wave lengths (Purkinje shift), and visual acuity depends on parafoveal blue cones. Shorter wavelengths come into focus in front of the retina, and this chromatic aberration accounts for some of the relative myopia that a normal eye experiences at night; much of the remainder is due to an increase in accommodative tone in the dark. Pathologic myopia, progressive myopia marked by fundus changes, posterior staphyloma, and subnormal corrected acuity. Synonym: degenerative myopia, malignant myopia. Prematurity myopia, myopia observed in infants of low birth weight or in association with retrolental fibroplasia. (05 Mar 2000)