Abstract
Purpose :
Some patients express a preference for visual aids that include a high pass spectral filter (HPSF) (Clark, 1969). Although not demonstrated directly, research suggests that a filter, such as that provided by macular pigment, may improve chromatic contrast (Hammond, Fletcher & Elliott, 2013). We hypothesize that some HPSFs enhance chromatic contrast sensitivity.
Methods :
To test this hypothesis, a single-site, subject-masked, 6x6 crossover, controlled, randomized, non-dispensing study was conducted. Heterochromatic flicker photometry (HCFP) was utilized to ensure that the stimuli were isoluminant. Results from the HCFP experiment were used to adjust the intensity of one component of the Gabor stimulus so that the stimuli were individualized for each subject. Each color axis was set at the nominal values, representative of the standard observer. Binocular chromatic contrast sensitivity functions (CCSFs) were measured along both the Protan (red-green) and Tritan (blue-yellow) axes with six different filters: UV control, ND control, 419nm HPSF, 437nm HPSF, 456nm HPSF, 476nm HPSF. Sensitivity thresholds were determined at seven spatial frequencies: 0.2, 0.4, 0.6, 1, 2, 4 and 6cpd. Both HCFP and CCSF experiments were conducted with a commercial visual function assessment system utilizing a 32in display located 1.5m from the subject (Metropsis, Cambridge Research Systems Ltd., Kent, UK). In total, 20 subjects completed the study per-protocol. The ratio of the area under the curve (AUC) of the CCSFs (test:control) were computed.
Results :
With Protan stimuli, AUC CCSF ratios were 1.07, 1.10, 0.93 and 0.92 for the 419nm, 437nm, 456nm, and 476nm HPSFs, respectively. With Tritan stimuli, AUC CCSF ratios were 0.87, 0.97, 0.74 and 0.73 for the 419nm, 437nm, 456nm, and 476nm HPSFs, respectively. Results demonstrate that HPSFs blocking components nominally below 440nm appear to improve CCSF along the Protan axis. Other, more aggressive, HPSFs decrease CCSF along the Tritan axis.
Conclusions :
Thus, we provide evidence that supports the notion that patient reported preferences for certain HPSFs are, at least in part, motivated by an improvement in chromatic contrast sensitivity.
This is a 2021 ARVO Annual Meeting abstract.