Developing a clinically viable protocol for measuring and analysing the human contrast sensitivity function on a standard computerised chart

Abstract

AbstractPurpose Contrast sensitivity testing is an important part of visual assessment and can identify visual deficits that go undetected by measuring visual acuity (VA) alone. Despite this, contrast sensitivity testing is rarely performed clinically due to the expensive processes required and limited test availability, with few spatial frequencies used. Further, gratings can be difficult for subjects to learn and results are often not standardized. We developed and tested a convenient, inexpensive protocol using Snellen optotypes to measure the CSF using a widely available computerised VA chart. Effects of blur and neutral density (ND) light attenuation were analysed to evaluate the technique under different conditions.Methods 34 eyes of 34 subjects were tested monocularly under photopic conditions. Subjects had corrected VA of 6/4.8 (or better) and normal ocular health. A computerised chart (Luneau) was used to measure contrast sensitivity thresholds across 19 spatial frequencies between 0.9 and 60.0 cpd using an ascending Method of Limits. This was repeated with +1.50DS blur and a 2.9 ND filter. CSFs were analysed and modeled using R and Prism to extract useful parameters: the area under the log10 CSF (AULCSF), CSF peak, high‐ and low‐spatial frequency limits.Results A quadratic function was found to best fit the pooled log CSF data, minimising cross‐validation error. The AULCSF was calculated between log spatial frequencies of 0.6 and 1.4 using integration of the fitted quadratic function. Mean AULCSF was 1.82±0.133.Conclusion Our method can measure, display and calculate the normal CSF. This can be used to compare and assess the CSFs of patients with ocular diseases.