Contrast sensitivity functions measured using simple optics and computer testing

Abstract

AbstractPurposeContrast sensitivity function (CSF) testing is a common approach to assessing clinical changes to specific aspects of spatial vision. Different stimulus presentations and testing procedures, however, yield significant differences in CSF curves that are more a feature of the method than the observer. In this study, we designed a simple optical device for measuring CSF that could be directly calibrated and compared with a commonly used computer‐based system.MethodsTwenty‐one participants (M = 28.95 ± 10.34 years; 66.7% female; 81.0% non‐Hispanic White; best corrected visual acuity 6/9 or better) provided photopic CSFs (from measurements at 1.6, 3.2, 8, 16 and 24 cycles per degree, with spatial frequency presentation randomised) using both the Metropsis test platform and a simple optical device over two test sessions (one session/method, randomised, counterbalanced) separated by 1–7 days. The optical system used 520 nm lasers that were made Lambertian using two integrating spheres with a 3.5° circular exit port. These beams were combined with a beam splitter that allowed constant measurement of light output and contrast modulation using sine‐wave gratings on glass. In Metropsis, 2° Gabor stimuli were presented for 0.5 s with either a vertical or a horizontal orientation via a two‐alternative forced choice paradigm with contrast modulated until four (first) and eight (last) reversals were complete.ResultsBoth methods took approximately the same amount of time to generate a CSF and yielded curves that were consistent with past studies using similar methods but different from each other. The optical system showed a 3.5 times higher maximum sensitivity and yielded higher test–retest reliability.ConclusionsUsing simple optics to measure CSF yields low noise, high sensitivity and reliability. The ability to calibrate the stimuli directly is an advantage over computer‐based methods.