The Contrast Sensitivity Function: From Laboratory to Clinic
The contrast sensitivity function (CSF), which describes visual sensitivity (1/contrast threshold) to narrow-band stimuli of different spatial frequencies, provides a comprehensive measure of the visual system over a wide range of spatial frequencies in both normal and abnormal vision. The CSF is closely related to daily visual functions and has proved important in characterizing functional deficits in many visual disorders. More importantly, assessment of CSF may reveal the “hidden vision loss”, that is, even when acuity appears normal, patients may have evident CSF deficits. I will discuss three lines of research: (1) Modeling: Using the external noise paradigm and the perceptual template model (PTM), we characterized the CSF in terms of the gain profile, nonlinearity, additive noise, and multiplicative noise of the perceptual system. (2) Efficient Assessment: Despite the importance of assessing the CSF, the testing time needed for precise assessment has prevented its clinical application. We developed the qCSF method, a novel Bayesian adaptive psychophysical method, that can be used to provide an accurate assessment of the full CSF in a few minutes. In addition, we have conducted a number of studies to improve and validate the method, and assess its precision, accuracy, specificity, and sensitivity. (3) Clinical Applications: The qCSF method has used in clinical settings and clinical trials to reveal hidden vision loss in a number of patient populations. I will provide a few example applications.