The effect of blue‐light blocking spectacle lenses on visual performance, macular health and the sleep‐wake cycle: a systematic review of the literature

<jats:title>Abstract</jats:title><jats:sec><jats:title>Purpose</jats:title><jats:p>Blue‐blocking (<jats:styled-content style="fixed-case">BB</jats:styled-content>) spectacle lenses, which attenuate short‐wavelength light, are being marketed to alleviate eyestrain and discomfort when using digital devices, improve sleep quality and potentially confer protection from retinal phototoxicity. The aim of this review was to investigate the relative benefits and potential harms of these lenses.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>We included randomised controlled trials (<jats:styled-content style="fixed-case">RCT</jats:styled-content>s), recruiting adults from the general population, which investigated the effect of <jats:styled-content style="fixed-case">BB</jats:styled-content> spectacle lenses on visual performance, symptoms of eyestrain or eye fatigue, changes to macular integrity and subjective sleep quality. We searched <jats:styled-content style="fixed-case">MEDLINE</jats:styled-content>,<jats:styled-content style="fixed-case"> EMBASE</jats:styled-content>, the Cochrane Library and clinical trial registers, until 30 April 2017. Risk of bias was assessed using the Cochrane tool.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Three studies (with 136 participants) met our inclusion criteria; these had limitations in study design and/or implementation. One study compared the effect of <jats:styled-content style="fixed-case">BB</jats:styled-content> lenses with clear lenses on contrast sensitivity (<jats:styled-content style="fixed-case">CS</jats:styled-content>) and colour vision (<jats:styled-content style="fixed-case">CV</jats:styled-content>) using a pseudo‐<jats:styled-content style="fixed-case">RCT</jats:styled-content> crossover design; there was no observed difference between lens types (log <jats:styled-content style="fixed-case">CS</jats:styled-content>; Mean Difference (<jats:styled-content style="fixed-case">MD</jats:styled-content>) = −0.01 [−0.03, 0.01], <jats:styled-content style="fixed-case">CV</jats:styled-content> total error score on 100‐hue; <jats:styled-content style="fixed-case">MD</jats:styled-content> = 1.30 [−7.84, 10.44]). Another study measured critical fusion frequency (<jats:styled-content style="fixed-case">CFF</jats:styled-content>), as a proxy for eye fatigue, on wearers of low and high <jats:styled-content style="fixed-case">BB</jats:styled-content> lenses, pre‐ and post‐ a two‐hour computer task. There was no observed difference between low <jats:styled-content style="fixed-case">BB</jats:styled-content> and standard lens groups, but there was a less negative change in <jats:styled-content style="fixed-case">CFF</jats:styled-content> between the high and low <jats:styled-content style="fixed-case">BB</jats:styled-content> groups (<jats:styled-content style="fixed-case">MD</jats:styled-content> = 1.81 [0.57, 3.05]). Both studies compared eyestrain symptoms with Likert scales. There was no evidence of inter‐group differences for either low <jats:styled-content style="fixed-case">BB</jats:styled-content> (<jats:styled-content style="fixed-case">MD</jats:styled-content> = 0.00 [−0.22, 0.22]) or high <jats:styled-content style="fixed-case">BB</jats:styled-content> lenses (<jats:styled-content style="fixed-case">MD</jats:styled-content> = −0.05 [−0.31, 0.21]), nor evidence of a difference in the proportion of participants showing an improvement in symptoms of eyestrain or eye fatigue. One study reported a small improvement in sleep quality in people with self‐reported insomnia after wearing high compared to low‐<jats:styled-content style="fixed-case">BB</jats:styled-content> lenses (<jats:styled-content style="fixed-case">MD</jats:styled-content> = 0.80 [0.17, 1.43]) using a 10‐point Likert scale. A study involving normal participants found no observed difference in sleep quality. We found no studies investigating effects on macular structure or function.</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>We find a lack of high quality evidence to support using <jats:styled-content style="fixed-case">BB</jats:styled-content> spectacle lenses for the general population to improve visual performance or sleep quality, alleviate eye fatigue or conserve macular health.</jats:p></jats:sec>