EFFECT OF MONOCHROMATIC ABERRATIONS ON PHOTOREFRACTIVE PATTERNS

Photorefractive methods have become popular in the measurement of refr active and accommodative states of infants and children owing to their photographic nature and rapid speed of measurement. As in the case of any method that measures the refractive state of the human eye, monoc hromatic aberrations will reduce the accuracy of the measurement. Mono chromatic aberrations cannot be as easily predicted or controlled as c hromatic aberrations during the measurement, and accordingly they will introduce measurement errors. This study defines this error or uncert ainty by extending the existing paraxial optical analyses of coaxial a nd eccentric photorefraction. This new optical analysis predicts that, for the amounts of spherical aberration (SA) reported for the human e ye, there will be a significant degree of measurement uncertainty intr oduced for all photorefractive methods. The dioptric amount of this un certainty may exceed the maximum amount of SA present in the eye. The calculated effects on photorefractive measurement of a real eye with a mixture of spherical aberration and coma are shown to be significant. The ability, developed here, to predict photorefractive patterns corr esponding to different amounts and types of monochromatic aberration m ay in the future lead to an extension of photorefractive methods to th e dual measurement of refractive states and aberrations of individual eyes.