ABSTRACT
A. INTRODUCTION Understanding the importance of contrast sensitivity can be easier if we emphasize its relationship to spatial vision, which is the core of the visual perception (1). Spatial frequency theory of image processing is based on spatially extended patterns called sinusoidal gratings, which are characterized by four parameters: spatial frequency, orientation, amplitude, and phase. The contrast sensitivity function is a measure of the observer’s sensitivity to gratings at different frequencies and is determined by the lowest contrast at which the sinusoidal gratings can still be detected (2). Over 200 years ago, contrast sensitivity began to be acknowledged as a clinical tool for doctors in studying visual disorders (3). In 1760 Bouguer defined and gave a value to the term light-difference threshold, the first denomination of contrast threshold. Since then other researchers have made a great number of contributions to this field: Bjerrum (1884) with letter charts, the first low-contrast letter acuity tests, and Young (1918) with the ink spot test, an easy method to measure the lightdifference threshold. More recently Schade (1956) applied his knowledge of television technology to contrast sensitivity testing. The work of Campbell and Green contributed to a better understanding of the optical and neural mechanism of contrast sensitivity testing contrast sensitivity in ocular diseases.
