THE EFFECT OF PUPIL AND OBSERVATION DISTANCE ON THE CONTRAST SENSITIVITY FUNCTION

Measuring the contrast sensitivity function (CSF) is becoming more fre quent in the analyses that are routinely done in optometric practice. This measurement is generally done in far vision, and the observation distance and its effects are not considered to significantly alter thi s function. Among these effects we should point out the accommodation of the visual optical system to the stimulus and the errors in accommo dation associated with this, changes in pupil diameter and therefore S pherical illumination when the observation distance changes, the diffe rent level of aberrations (spherical aberration, astigmatism) for diff erent cases, and so on. All of these factors contribute to the fact th at the contrast sensitivity of a visual system varies according to the accommodative stimulus. In this study we attempt to clarify the influ ence of these different parameters by evaluating the CSF for three obs ervation distances. The study was done in monocular vision, with a nat ural pupil and with a 3 mm artificial pupil that made it possible to m aintain the same level of retinal illumination for all distances. Copy right (C) 1996 The College of Optometrists. Published by Elsevier Scie nce Ltd.