Clinical relevance: Wearing blue-blocking lenses (BBLs) in the evening hours may not be effective in improving sleep quality. Optometrists need to be informed in prescribing BBLs by highlighting the consequences of their wear to the circadian system.
Background: Excessive exposure to artificial light, particularly at short wavelengths, during the evening, may disrupt normal nocturnal melatonin production, which is a natural process of the circadian rhythm and affect sleep quality. Current BBLs have been designed to limit blue-light exposure and may offer a means to minimise disruption to the circadian system. The purpose of this study was to evaluate the impact of BBLs on a normal sleep-wake circadian rhythm.
Methods: Seven different commercial brands of BBLs (Crizal Prevencia, Smart Blue Filter, Blu-OLP, Blue Control, UV++Blue Control, SeeCoat Blue UV and Blue Guardian) and powers (+2.00 D, -2.00 D and Plano) were evaluated by quantifying the degree to which they reduce light radiation from lamps and electronic devices. In particular, the non-linear circadian index and the circadian stimulus was determined for various light sources to establish changes in melatonin production that occur while viewing through different BBLs.
Results: A large difference was shown in the effectiveness of different BBL brands in reducing the spectral sensitivity of the circadian system. The BBL brand was shown to selectively affect the non-linear circadian index and circadian stimulus, particularly with those with transmittance profiles that block the most blue light having the lowest effect on the suppression of nocturnal melatonin secretion.
Conclusion: BBLs may not improve sleep quality, because they continue to allow the transmittance of blue light that may suppress nocturnal melatonin secretion and hence disrupt the normal sleep-wake circadian rhythm.
Keywords: Blue-blocking lenses; circadian system; nocturnal melatonin suppression.