Effect of blue-blocking lenses on colour contrast sensitivity

Clinical relevance There is a significant unintended consequences of blue-blocking lenses on visual behaviour, particularly for the detection of colour. Optometrists need to be mindful of this when prescribing the appropriate blue-blocking lenses for individuals who work in environments in which blue light is prevalent. Background The selective reduction in visible wavelengths transmitted through commercially available blue-blocking lenses is known to influence object appearance and luminance contrast, and also potentially object colour contrast. The present study investigated the effect of a number of commercially available blue-blocking lenses on colour contrast sensitivity in normal individuals under low and high contrast stimulus conditions. Methods Five healthy participants (one man and four women), aged between 23 and 39 years, were recruited for this study. Crizal Prevencia (Essilor), Blue Guardian (Opticare), and Blu-OLP (GenOp) lenses were examined in this study in comparison to a control lens (clear lens without blue-filtering coating). In Experiment 1, colour contrast thresholds were measured using a visual search colour detection task in which the colour (CIE Lu'v' red, green, blue and yellow) of the target circle stimulus (randomly located in an annulus of achromatic circles) was systematically reduced using a staircase procedure. As blue-blocking lenses selectively block blue light, in Experiment 2, colour contrast thresholds were specifically quantified for a range of short wavelengths near the attenuation transmittance range of the blue-blocking lenses tested. Results Experiments 1 and 2 showed that colour contrast was impaired only for blue colours, and this was most evident at low contrasts. Additionally, the blue-blocking lenses with lower transmittance profiles led to greater reductions in colour contrast sensitivity and shown to affect colour contrast thresholds. Conclusion Our results suggest that while reducing blue light potentially minimises the harmful effect of blue hazard light, blue-blocking lenses can unintentionally reduce colour contrast sensitivity, particularly at low light levels.