PURPOSE: The contrast sensitivity function (CSF) can be used to assess even subtle changes in visual function. These changes are likely amplified in the presence of a stressor such as glare. In this study, we tested mesopic and photopic CSF in the absence/presence of an ecologically valid glare source. CSF was tested within subjects, comparing a high energy visible (HEV)-filtering contact lens against a clear comparator lens of similar material and design. METHODS: This was a randomized, controlled, and double-masked study. Forty participants (19-65 years) provided photopic (n=20) or mesopic (n=20) CSF (1.6, 3.2, 8, 16, and 24 cpd) both with and without veiling glare. CSF was measured using a customized optical system. Two separate light channels were combined with a beam splitter that allowed contrast modulation using sine-wave gratings on glass. Glare was interposed between the grating and the subject's eye using an ancillary xenon-based optics channel. RESULTS: The mean area under the CSF curve derived for both photopic and mesopic CSF (with and without glare) was significantly improved by use of the HEV-absorbing lens compared with the control. With a glare source, the least-squares mean differences (95% confidence interval) were 0.3 (0.24-0.36) and 0.14 (0.10-0.18) under photopic and mesopic conditions, respectively. In the absence of a glare source, the least-squares mean differences (95% confidence interval) were 0.26 (0.21-0.31) and 0.28 (0.20-0.37) for photopic and mesopic conditions, respectively. CONCLUSION: The HEV-absorbing lens significantly improved CSF when tested under mesopic and photopic conditions and both with and without veiling glare.
Hammond et al. (Fri,) studied this question.