Night myopia.

Although the phenomenon of night myopia has been recognized for two centuries, its causes are still not fully understood. Early studies implicated spherical aberration and accommodation, but the degree to which either contributed was not clearly established. More recently, "laser speckle" techniques to measure myopia have allowed the collection of data on large subject populations and it appears that night myopia represents a tendency for accommodation to approximate the dark focus as low luminance levels degrade the clarity of the retinal image. In this article, the authors review the past and present literature on night myopia and related anomalous myopias, and describe techniques for their evaluation and correction.