Next-generation vision testing: the quick CSF

Abstract

The Contrast Sensitivity Function relates the spatial frequency and contrast of a spatial pattern to its visibility and thus provides a fundamental description of visual function. However, the current clinical standard of care typically restricts assessment to visual acuity, i.e. the smallest stimulus size that can be resolved at full contrast; alternatively, tests of contrast sensitivity are typically restricted to assessment of the lowest visible contrast for a fixed letter size. This restriction to one-dimensional subspaces of a two-dimensional space was necessary when stimuli were printed on paper charts and simple scoring rules were applied manually. More recently, however, computerized testing and electronic screens have enabled more flexible stimulus displays and more complex test algorithms. For example, the quick CSF method uses a Bayesian adaptive procedure and an information maximization criterion to select only informative stimuli; testing times to precisely estimate the whole contrast sensitivity function are reduced to 2-5 minutes. Here, we describe the implementation of the quick CSF method in a medical device. We make several usability enhancements to make it suitable for use in clinical settings. A first usability study shows excellent results, with a mean System Usability Scale score of 86.5.

Keywords

• vision
• contrast sensitivity function
• adaptive methods