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The effect of blue-light blocking spectacle lenses on visual
performance, macular health and the sleep-wake cycle:
a systematic review of the literature
John G Lawrenson
1
, Christopher C Hull
1
and Laura E Downie
2
1
Centre for Applied Vision Research, Division of Optometry and Visual Science, City University of London, London, UK, and
2
Department of
Optometry and Vision Sciences, The University of Melbourne, Melbourne, Victoria, Australia
Citation information: Lawrenson JG, Hull CC & Downie LE. The effect of blue-light blocking spectacle lenses on visual performance, macular health
and the sleep-wake cycle: a systematic review of the literature. Ophthalmic Physiol Opt 2017; 37: 644–654. https://doi.org/10.1111/opo.12406
Keywords: blue light blocking, macular
changes, sleep-wake cycle, spectacles,
systematic review, visual performance
Correspondence: John G Lawrenson
E-mail address: j.g.lawrenson@city.ac.uk
Received: 6 June 2017; Accepted: 17 August
2017
Abstract
Purpose: Blue-blocking (BB) 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 pho-
totoxicity. The aim of this review was to investigate the relative benefits and
potential harms of these lenses.
Methods: We included randomised controlled trials (RCTs), recruiting adults
from the general population, which investigated the effect of BB spectacle lenses
on visual performance, symptoms of eyestrain or eye fatigue, changes to macular
integrity and subjective sleep quality. We searched MEDLINE, EMBASE, the
Cochrane Library and clinical trial registers, until 30 April 2017. Risk of bias was
assessed using the Cochrane tool.
Results: Three studies (with 136 participants) met our inclusion criteria; these
had limitations in study design and/or implementation. One study compared the
effect of BB lenses with clear lenses on contrast sensitivity (CS) and colour vision
(CV) using a pseudo-RCT crossover design; there was no observed difference
between lens types (log CS; Mean Difference (MD) =0.01 [0.03, 0.01], CV
total error score on 100-hue; MD =1.30 [7.84, 10.44]). Another study mea-
sured critical fusion frequency (CFF), as a proxy for eye fatigue, on wearers of low
and high BB lenses, pre- and post- a two-hour computer task. There was no
observed difference between low BB and standard lens groups, but there was a less
negative change in CFF between the high and low BB groups (MD =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 BB (MD =0.00 [0.22,
0.22]) or high BB lenses (MD =0.05 [0.31, 0.21]), nor evidence of a differ-
ence 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-BB
lenses (MD =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.
Conclusions: We find a lack of high quality evidence to support using BB specta-
cle lenses for the general population to improve visual performance or sleep qual-
ity, alleviate eye fatigue or conserve macular health.
©2017 The Authors Ophthalmic & Physiological Optics ©2017 The College of Optometrists
Ophthalmic & Physiological Optics 37 (2017) 644–654
644
Ophthalmic & Physiological Optics ISSN 0275-5408
Introduction
Rationale
Studies, in animal models
1,2
and cell culture,
3,4
have
shown that wavelengths in the blue portion of the electro-
magnetic spectrum (400–500 nm) can induce phototoxic
retinal damage. Historically, two mechanisms of photo-
chemical damage have been recognised and eponymously
named as ‘Noell damage’ and ‘Ham damage’ after the
original investigators.
1,5
Noell, or Class I, damage was first
observed following prolonged exposure of albino rats to
fluorescent light (490–580 nm). Cellular disruption
occurred initially in photoreceptors, followed by the reti-
nal pigment epithelium (RPE). By contrast, Ham
5
(Class
II damage) described disruption that occurred after
shorter, high intensity light exposures (between 10 s and
2 h’ duration). Shorter wavelengths were associated with
more intense cellular damage, initially at the level of the
RPE, with a peak of the action spectrum occurring at
around 440 nm in the phakic eye. International standards
have been developed based on these empirical studies
6
,
which define exposure limits, below which adverse effects
are unlikely to occur. However, driven by requirements
for brighter and lower energy lighting, the last 10 years
has seen significant changes in light sources for both com-
mercial and domestic applications, with an increased use
of compact fluorescent lamps (CFL) and high intensity
light-emitting diodes (LEDs). Moreover, white-light LEDs
(the most common type of LED) have become ubiquitous
in backlit displays in smartphones and tablet computers.
Although the light emitted by these LEDs appears white,
their emission spectra show peak emissions at wavelengths
corresponding to the peak of the blue light hazard func-
tion. It has been shown that exposure of cultured RPE
cells to light equivalent to that emitted from mobile dis-
play devices causes increased free radical production and
reduced cell viability.
7
This has raised concerns that the
cumulative exposure to blue light from such sources may
induce retinal toxicity and potentially increase the risk of
age-related macular degeneration.
8
The rationale for the introduction of blue-blocking oph-
thalmic lenses was to mitigate the risk of retinal toxicity by
blocking, or attenuating, short wavelength visible light, usu-
ally in the range 400 nm to 500 nm. These ophthalmic
devices, which include spectacle lenses, contact lenses and
intra-ocular lenses (IOLs), contain or are coated with dyes
that selectively absorb blue and violet light. The choice
between a conventional ultraviolet (UV) light blocking IOL
and a blue-blocking IOL following cataract surgery has gener-
ated significant debate in the literature in terms of achieving a
balance between photoreception and photoprotection.
9–12
Possible disadvantages of blocking short-wavelength visible
light transmission include disturbances of colour perception,
decreased scotopic sensitivity (leading to poorer performance
in dim lighting conditions) and disruption of the timing of
the circadian system.
13
Intrinsically photosensitive retinal gan-
glion cells, which provide photic input to the central circadian
clock in the suprachiasmatic nucleus, express melanopsin and
have an absorption peak at approximately 480 nm in the blue
part of the spectrum.
14
Compared to their intra-ocular counterpart, blue-block-
ing spectacle lenses have received relatively little scientific
attention. Standard spectacle lenses generally offer protec-
tion against UV (up to wavelengths of 380 nm) and the
adding of a yellow chromophore can also reduce or elimi-
nate blue light transmission. Alternatively, anti-reflection
interference coatings can be applied to both the anterior
and posterior lens surfaces, to selectively attenuate parts of
the blue-violet light spectrum (415 to 455 nm); this range
of wavelengths includes a significant proportion of the blue
light hazard function
15
, while the lens remains transparent
to other wavelengths of visible light. In addition to their
putative benefit for retinal protection, blue-blocking spec-
tacle lenses have also been claimed to improve sleep quality
following the use of electronic devices at night,
16
and
reduce eye fatigue and symptoms of eye strain during
intensive computer tasks.
17
A systematic review of the best available research evi-
dence is essential to assess the appropriateness of marketing
blue-blocking spectacle lenses at the general spectacle wear-
ing population. This evaluation will consider both the rela-
tive benefits and potential harms of these lenses.
Objectives
The primary aim of this systematic review is to evaluate the
effectiveness of blue-blocking spectacle lenses for improv-
ing visual performance and reducing visual fatigue. Our
secondary aims are to assess whether these lenses are effec-
tive in maintaining macular health and to determine any
positive or negative effects on the sleep-wake cycle. The
review will attempt to find scientific evidence to answer the
following questions:
1. Compared to standard (non blue-blocking) spectacle
lenses, do blue-blocking lenses enhance visual perfor-
mance?
2. Compared to standard spectacle lenses, do blue-block-
ing lenses improve visual comfort and/or reduce symp-
toms of visual fatigue?
3. What is the evidence that blue-blocking spectacle lenses
provide protection to the macular and preserve macular
function?
4. What is the evidence that blue-blocking spectacle lenses
disrupt circadian entrainment and affect alertness and/
or sleep quality?
©2017 The Authors Ophthalmic & Physiological Optics ©2017 The College of Optometrists
Ophthalmic & Physiological Optics 37 (2017) 644–654
645
J G Lawrenson et al. Blue-light blocking spectacle lenses
Methods
The protocol for this review was prospectively published
on PROSPERO (2017:CRD42017064117) Available from
http://www.crd.york.ac.uk/PROSPERO/display_record.asp?
ID=CRD42017064117),
Search strategy
We conducted searches using the following bibliographic
databases: Ovid MEDLINE, Ovid EMBASE, PubMed and
the Cochrane Library for relevant articles published before
May 2017. We did not use any date or language restric-
tions for the bibliographic searches. An example search
strategy for one of the databases (Ovid MEDLINE) is
included in File S1. We also scanned the reference list of
included studies and contacted experts in the field to ask
if they were aware of additional published or on-going
trials investigating blue-blocking lenses. We searched the
PROSPERO database for relevant systematic reviews and
searched clinical trials registries (Clinical trials.gov and
the ISRCTN registry) for recently completed or on-going
trials.
Inclusion and exclusion criteria
We included randomised controlled trials (RCTs) and
pseudo-randomised controlled trials, which recruited adults,
aged 18 years and above, from the general population and
compared blue-blocking spectacle lenses to standard specta-
cles lenses, or any other comparator, where it was possible to
isolate the effect of the blue-blocking lens for any of our pri-
mary or secondary outcomes. The review team decided
post-hoc that this should include comparisons between high
and low blue-blocking lenses. We defined blue-blocking
lenses as those that block or attenuate short wavelength opti-
cal radiation between 400 nm and 500 nm.
The following outcomes were considered:
Primary outcomes:
1. Any measure of visual performance (e.g., logMAR visual
acuity, contrast sensitivity, critical fusion frequency
(CFF), colour discrimination under photopic or meso-
pic conditions, scotopic sensitivity, dark adaptation,
stray light and glare sensitivity) conducted during the
follow up period of the trial.
2. Any measure of visual fatigue or discomfort (e.g., using
questionnaires or visual analogue scales) conducted
during the follow-up period of the trial.
Secondary outcomes:
1. Proportion of eyes with a structural change in the mac-
ula using clinical observation, fundus photography or
optical coherence tomography (OCT) between six and
24 months following the start of the intervention. This
could include development of early AMD, progression
of AMD or progression to late stage AMD, as defined by
the trial investigators.
2. Objective or subjective assessment of alertness and/or
sleepiness.
3. Effect on average macular pigment optical density
(MPOD), measured as the proportion of eyes that had a
significant increase in MPOD at six months.
4. Overall participant satisfaction with blue-blocking
lenses (e.g., using questionnaires or rating scales).
Adverse effects:
1. Any ocular and systemic adverse effects associated with
the intervention, as reported by the study authors.
For the evaluation of visual performance and effect of the
intervention on alertness and/or sleep quality, we included
any measure conducted during the follow-up period of the
trial. To assess the effects of blue-blocking spectacle lenses
on macular health or function, studies had to be at least
6 months duration.
Data extraction and analysis
Following removal of duplicates, two reviewers (JL and
CH) independently screened the titles and abstracts identi-
fied from the bibliographic searches and resolved any
discrepancies by discussion and consensus. We obtained
full-text copies of potentially eligible studies and these were
assessed by both reviewers to decide whether they met the
inclusion criteria. Reasons for exclusion were documented
at this stage. We used a data extraction form that was devel-
oped and piloted for the purpose of this review. We col-
lected data on: study design, details of participants, details
of intervention, methodology, quantitative data on out-
comes and funding sources. Data extraction was conducted
independently by two reviewers (JL and CH) and any dis-
crepancies resolved by discussion. The extracted numerical
data was entered into Revman 5
18
meta-analytical software
by one reviewer (JL) and this was checked by a second
reviewer (CH).
Two review authors (JL and CH) independently assessed
the risk of bias in included studies using the Cochrane Risk
of Bias tool as detailed in Chapter 8 of the Cochrane Hand-
book.
19
We evaluated risk of bias using the following bias
domains:
1. Selection bias (random sequence generation and alloca-
tion concealment);
2. Performance bias (masking of participants and personnel);
3. Detection bias (masking of outcome assessment);
4. Attrition bias (incomplete outcome data);
©2017 The Authors Ophthalmic & Physiological Optics ©2017 The College of Optometrists
Ophthalmic & Physiological Optics 37 (2017) 644–654
646
Blue-light blocking spectacle lenses J G Lawrenson et al.
5. Reporting bias (selective reporting of outcomes);
6. Other bias (funding source, other conflicts of interest).
Any differences of opinion in risk of bias assessments
were resolved by discussion.
Our measure of treatment effect was the risk ratio (RR)
for dichotomous outcomes and the mean difference (MD)
for continuous outcomes, with 95% confidence intervals
[CIs].
By definition, the intervention was applied to the person
and therefore the unit of analysis was the same as the unit
of randomisation. However, where data was presented from
both eyes, we analysed the data from the right eye only to
avoid a unit of analysis error. Insufficient studies were
available to conduct the planned meta-analysis. However a
descriptive summary of the results of the included studies
has been provided. Publication bias could not be assessed,
as there were an insufficient number of studies to conduct
this analysis.
We assessed the certainty of the evidence using the
Grades of Recommendation, Assessment and Evaluation
(GRADE) Working Group approach,
20
using customised
software (GRADEpro GDT). One reviewer (JL) conducted
the initial assessment and this was checked by the other
reviewers (CH and LD). We considered risk of bias,
inconsistency, indirectness, imprecision, and publication
bias when judging the certainty of the evidence.
Results
Results of the searches
The electronic searches yielded 118 references (see Figure 1
for the PRISMA flow diagram). After 19 duplicates were
removed, we screened the remaining 99 references and
obtained the full-text reports of 15 references for further
assessment. Twelve of these
17,21–31
were eliminated (see
Table of Excluded Studies in File S2 and three RCTs that
met the a priori criteria for inclusion were included in the
final analysis (see Characteristics of Included Studies in
File S3. We did not identify any on-going studies from our
searches of the clinical trials registries.
Characteristics of included studies
We included three studies in this review.
32–34
Two of the
studies were conducted in the USA and one in Hong Kong.
Burkhart and Phelps
32
randomised 20 adult volunteers
reporting sleep difficulty to wear either amber tinted glasses
(blocking wavelengths <550 nm) or yellow tinted placebo
Records idenfied through
database searching
(n = 118)
Addional records idenfied
through other sources
(n = 0)
Records aer duplicates removed
(n = 99)
Records screened
(n =99)
Records excluded
(n =84)
Full-text arcles assessed
for eligibility
(n =15)
Full-text arcles excluded,
with reasons
(n = 12)
Not RCT n=8
Primary and secondary
outcomes not reported n=3
Study included pseudophakes
only n=1
Included studies
(n =3)
ScreeningIncluded Eligibility Idenficaon
Figure 1. Study flow diagram.
©2017 The Authors Ophthalmic & Physiological Optics ©2017 The College of Optometrists
Ophthalmic & Physiological Optics 37 (2017) 644–654
647
J G Lawrenson et al. Blue-light blocking spectacle lenses
glasses (blocking wavelengths <465 nm) for three hours
prior to sleep. The primary outcome measure was sleep
quality as determined by sleep diaries, which incorporated
a 10-point Likert sleep quality scale. Sleep diaries were
completed for 1 week prior to the intervention (baseline)
and for 2 weeks afterwards.
Leung and co-workers
33
conducted a pseudo-randomised
controlled trial involving 80 computer users from two age
cohorts: young adults, 18–30 years, n=40 and middle aged
adults 40–55 years, n=40. Participants were randomised
into one of three groups to assess the performance of two
blue-blocking spectacle lenses (blue-blocking anti-reflection
coating and a brown tinted lens) and a regular clear control
lens, using a crossover design. The primary outcomes were
contrast sensitivity, using the Mars contrast sensitivity letter
chart under standard and glare conditions, and colour dis-
crimination using the Farnsworth-Munsell 100-hue test.
Following the visual assessment tests, participants wore each
assigned lens for one month for a minimum of two hours
per day. At the end of each wearing period, lens perfor-
mance was subjectively assessed using a 13-item question-
naire. Each question was rated on a 1–5 scale (where
1=very unsatisfactory and 5 =very satisfactory).
Lin and co-workers
34
recruited 36 adult subjects who were
randomised to one of three groups and wore either specta-
cles with low or high blue-blocking lenses or non-blue block-
ing lenses for a 2 h computer task using a laptop computer.
At the end of the task, critical fusion frequency (CFF) was
assessed and symptoms of eyestrain were evaluated using a
15-item questionnaire. The CFF is the lowest level of contin-
uous flicker that is perceived as a steady source of light and a
reduction in CFF was interpreted as a measure of eye fatigue.
Risk of bias and certainty of the evidence
We evaluated the risk of bias in the included studies using
the Cochrane risk of bias tool.
19
Figures 2 and 3 present a
graph and summary of the risk of bias for the included
studies. Overall the studies were at an unclear or high risk
of bias. We rated two studies
32,34
as having an unclear risk
of selection bias, since they did not describe the method for
random sequence generation or how this was concealed.
Leung and colleagues
33
allocated participants to different
sequences of lens wear by date of admission and therefore
the sequence was non-random and at a high risk of selec-
tion bias. Given that two of the included studies ran-
domised small numbers of participants,
32,34
there were
baseline differences in the outcome of interest, which may
have affected the results. Although attempts were made to
mask outcome assessors to the intervention received, it was
not possible to mask participants due to differences in
appearance between the lenses being tested. We judged one
study
34
to be at a high risk of selective reporting bias, due
to a failure to report on 2/15 of the questions from the
symptom questionnaire and no protocol or trial registra-
tion was available. Two studies
32,33
were judged to be at an
unclear risk of selective reporting since either no protocol
or trial registry entry was available, or in one case the trial
was retrospectively registered.
33
We rated the certainty of evidence for each outcome
using GRADE (see Table 1).
Effects of the intervention
Primary outcome measures
Two studies
33,34
randomising 116 participants, provided
data on differences in visual performance with blue-block-
ing lenses compared to a clear control lens. Leung et al
33
investigated the effect of blue-blocking lenses on contrast
sensitivity and colour vision using a crossover design. There
was no evidence of a difference in log contrast sensitivity or
total error score on the FM 100-hue test between the inter-
vention and control lenses (Table 1). Lin et al
34
measured
CFF (a proxy measure of eye fatigue) before and after a
Figure 2. Risk of bias graph presented as a % across all included studies. Green = Low risk of bias; Yellow = Unclear risk of bias; Red = High risk of
bias.
©2017 The Authors Ophthalmic & Physiological Optics ©2017 The College of Optometrists
Ophthalmic & Physiological Optics 37 (2017) 644–654
648
Blue-light blocking spectacle lenses J G Lawrenson et al.
two-hour computer task. There was no observed difference
between the low-blocking and no-blocking (clear) lens
groups, but there was evidence of a less negative change in
CFF between the high and low-blocking lens groups indi-
cating less fatigue with computer use for the high-block
group (Figure 4).
These studies also compared symptoms of eyestrain for
the intervention and control lenses using Likert rating
scales.
33,34
Leung et al.
33
measured symptoms of eyestrain
on a 5-point scale after 1 month of wearing low blue-
blocking (blue-filtering anti-reflection coating), high blue-
blocking (brown-tinted) or control (non blue-blocking)
lenses. There was no significant difference between the
intervention and control lenses for either the low blue-
blocking lens (Mean difference (MD) =0.00 [0.22, 0.22])
or the high blue-blocking lens (MD =0.05 [0.31,
0.21]). Lin et al
34
compared symptoms related to eye fati-
gue or eye strain before and after a two hour computer task
for participants wearing clear (control) lenses or low or
high blue-blocking lenses using a 15-item questionnaire.
Since there was no statistical difference between the low
blue-blocking and clear lens groups, the study authors
pooled the data for the low blue-blocking and clear lens
participants and compared the symptom scores, after the
task, for each question. Statistical differences between
groups, for each questionnaire item, were then investigated
using the Mann–Whitney Utest. For the current review, we
analysed the ordinal data from the 13 questionnaire items
reported and calculated the proportion of subjects in each
group showing a post-task symptomatic improvement for
each question. The risk ratio (RR) with 95% confidence
intervals was calculated for each question using Revman
18
(Table 2). A significant symptomatic improvement was
found for only one question ‘My eyes feel itchy’ (RR 2.68
[1.32, 5.44]).
Secondary outcomes
There was no available data on the proportion of eyes with
any structural change in the macula or the effect of blue-
blocking spectacle lenses on average MPOD.
Two studies provided data on the subjective assessment
of sleep quality. Leung et al.
33
found no evidence of a dif-
ference in sleep quality for low or high blue-blocking lenses
compared to control lenses for normal participants (low
blue-blocking, MD =0.04 [0.26, 0.18]; high blue-block-
ing, MD =0.00 [0.23, 0.23]). By contrast, Burkhart and
Phelps
32
found a small improvement in sleep quality in
participants wearing high blue-blocking lenses compared to
low blue-blocking lenses in individuals experiencing sleep-
onset or mid-sleep insomnia (MD =0.80 [0.17, 1.43]).
One study
33
reported on the overall performance of
blue-blocking lenses. There was no evidence of a difference
in performance for either low or high blue-blocking lenses
compared with control lenses.
None of the included studies reported on ocular or sys-
temic adverse effects associated with the interventions.
Discussion
Blue-blocking spectacle lenses, with varying degrees of
short-wavelength light attenuation (ranging from 10% to
100%), are being marketed at the general population with
claims that they can alleviate eyestrain and discomfort (par-
ticularly when using computers and other digital devices),
improve sleep quality and possibly confer protection from
retinal phototoxicity. The current systematic review did not
identify any high quality clinical trial evidence to support
these claims. Rather, the included studies provided evi-
dence, albeit of low certainty, that there was no significant
difference in relation to the proportion of subjects showing
an improvement in symptoms of eyestrain or eye fatigue
between the intervention (blue-blocking) and control spec-
tacle lenses. This conclusion differs from the authors of one
of the included studies. Using Likert scales, Lin and
colleagues compared symptoms in subjects wearing
high-blocking lenses to a combined low block/no block
group following a two hour computer task. They found
symptomatic improvement for the high block group in
three of the 15 questionnaire items (pain around/inside the
eye, eyes were heavy and the eyes were itchy) following the
Figure 3. Risk of bias for included studies.
©2017 The Authors Ophthalmic & Physiological Optics ©2017 The College of Optometrists
Ophthalmic & Physiological Optics 37 (2017) 644–654
649
J G Lawrenson et al. Blue-light blocking spectacle lenses
Table 1. Results table for primary and secondary outcomes
Outcome Study Comparison
Number of
participants Intervention effect
Certainty of
evidence
(GRADE
20
)
Any measure of visual
performance conducted during
the follow up period of the trial.
Leung 2017 Low blue-block vs.
clear lens
80 Log contrast sensitivity (combined
young and middle aged subjects)
MD =0.01 [CI 0.03, 0.01]
LOW
1
Leung 2017 High blue-block vs.
clear lens
80 Log contrast sensitivity (combined
young and middle aged subjects)
MD =0.01 [CI 0.03, 0.01]
Leung 2017 Low blue-block vs.
clear lens
80 Colour vision (TES) (combined
young and middle aged subjects)
MD =4.03 [CI 4.96, 13.02]
Leung 2017 High blue-block vs.
clear lens
80 Colour vision (TES) (combined
young and middle aged subjects)
MD =1.30 [CI 7.84, 10.44]
Lin 2017 Low blue-block vs.
clear lens
36 CFF pre- and post-task
MD =0.33 [CI1.61, 0.95]
Lin 2017 High blue-block vs.
clear lens
36 CFF pre- and post-task
MD =1.81 [CI 0.57, 3.05]
Any measure of visual fatigue or
discomfort conducted during the
follow-up period of the trial.
Leung 2017 Low blue-block vs.
clear lens
80 Relief of eyestrain (combined young
and middle aged subjects)
MD =0.00 [CI 0.22, 0.22]
LOW
1
Leung 2017 High blue-block vs.
clear lens
80 Relief of eyestrain (combined young
and middle aged subjects)
MD =0.05 [CI0.31, 0.21]
Lin 2017 High blue-block vs.
not high blue-block
36 Proportion showing an
improvement in symptoms of
eyestrain/eye fatigue pre- and
post-task. ‘My eyes feel tired’
RR =3.33 [0.95, 11.66]; ‘I feel
pain around or inside my eyes’
RR =2.60 [0.85, 7.98]; ‘My eyes
feel heavy’ RR =2.50 [0.95, 6.57].
Objective or subjective
assessment of alertness/and/or
sleepiness.
Leung 2017 Low blue-block vs.
clear lens
80 Sleep quality (combined young and
middle aged subjects)
MD =0.04 [CI 0.26, 0.18]
VERY LOW
1,2
Leung 2017 High blue-block vs.
clear lens
80 Sleep quality (combined young and
middle aged subjects)
MD =0.00 [CI0.23, 0.23]
Burkhart 2009 High blue-block vs.
low blue-block
20 Improvement in sleep quality
MD =0.80 [CI 0.08, 1.52]
Overall participant satisfaction
with blue-blocking lenses
Leung 2017 Low blue-block vs.
clear lens
80 Overall lens performance
MD =0.14 [CI0.36, 0.08]
LOW
1
Leung 2017 High blue-block vs.
clear lens
80 Overall lens performance
MD =0.05 [CI 0.17, 0.27]
Proportion of eyes with a
structural change in the macula
following the start of the
intervention.
Not reported N/A N/A N/A N/A
Effect on average macular
pigment optical density (MPOD).
Not reported N/A N/A N/A N/A
CFF, critical fusion frequency; MD, mean difference; RR, risk ratio; TES,total error score; N/A, not applicable.
A GRADE certainty of evidence rating of ‘low’ indicates that our confidence in the effect estimate is limited; the true effect may be substantially differ-
ent from the estimate of the effect. A GRADE certainty of ‘very low’ indicates that we have very little confidence in the effect estimate; the true effect
is likely to be substantially different from the estimate of effect.
1
Downgraded two levels for risk of bias.
2
Downgraded one level for indirectness.
©2017 The Authors Ophthalmic & Physiological Optics ©2017 The College of Optometrists
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Blue-light blocking spectacle lenses J G Lawrenson et al.
computer task, compared to subjects not wearing high-
blocking lenses. However, the authors did not indicate
whether this analysis was pre-specified or was part of an
exploratory post-hoc comparison. Furthermore, there was
no suggestion that the authors had considered the risk of a
type I error associated with multiple statistical compar-
isons.
35
For the current study we used the analysis plan that
was specified prospectively in the review protocol (PROS-
PERO 2017:CRD42017064117). In addition, we also con-
sidered that it would be statistically more appropriate and
clinically more meaningful to present the data from Lin
et al
34
as a comparison of the proportion of subjects show-
ing a post-task symptomatic improvement for each item in
the questionnaire, given that we do not accept that the
questionnaire responses can reasonably be considered to
fall on a continuous scale.
Subjective ratings of overall lens performance were
reported in one crossover trial in which 80 participants
wore spectacles with low blue-blocking, high blue-blocking
or control (clear) lenses for 4 weeks. There was no observed
difference in performance ratings between lens types. A
parallel group RCT reported that high blue-blocking lenses
(but not low blue-blocking lenses) produced a less pro-
nounced reduction in CFF after a two-hour computer task
indicating less visual fatigue. However, the clinical signifi-
cance of this finding is unclear, since CFF has been shown
to decline after reading irrespective of whether the task is
performed on paper or using an e-reader. This suggests that
the CFF parameter may be independent of blue light
exposure.
36
In modern society, computers and other digital elec-
tronic devices are ubiquitous in both the workplace and
domestic environments and given the high number of
hours per day that most individuals spend viewing small
text on electronic devices at short working distances, it is
not surprising that up to 90% of users periodically experi-
ence asthenopic symptoms including, eyestrain, headaches,
ocular discomfort, dry eye, diplopia and blurred vision.
37
However, what is now termed computer (or digital) vision
syndrome is a multifactorial condition with several poten-
tial contributory causes, such as uncorrected refractive
error, oculomotor disorders, tear film abnormalities and/or
musculoskeletal problems.
38
Therefore, the role played by
blue light in these symptoms is difficult to extricate.
Despite the putative benefits of blue light blocking lenses,
concerns have been raised that these lenses could adversely
affect some aspects of visual performance (e.g., contrast
sensitivity or colour vision). Using standard clinical tests,
Leung et al.
33
did not observe any detrimental effects on
log-contrast sensitivity or total error score using the FM
100-hue colour vision test. This is consistent with a previ-
ous systematic review
39
and meta-analysis comparing blue-
blocking IOLs with UV-blocking IOLs, following cataract
surgery. The results showed that there was no evidence of
any difference in post-operative contrast sensitivity or over-
all colour vision, although colour vision with blue-blocking
IOLs was impaired at the blue end of the spectrum under
mesopic conditions.
39
Figure 4. Comparison of change in Critical Fusion Frequency (CFF), in Hz, before and after a computer task for high and low blue-blocking lenses
versus control. The high blue-blocking lens is associated with a significant change in CFF. Data from the same control group are used in both
comparisons.
Table 2. Analysis of symptom questionnaire from Lin et al
34
comparing
subjects wearing high blue blocking lenses to those wearing low blue-
blocking or clear lenses
Question RR (95%CI)
I feel pain around or inside my eyes 2.60 [0.85, 7.98]
My eyes feel heavy 2.50 [0.95, 6.57]
My eyes feel itchy 2.68 [1.32, 5.44]
My eyes feel tired 3.33 [0.95, 11.66]
I find it hard to focus my eyesight 1.75 [0.83, 3.67]
I see written or computer text as blurry 1.67 [0.54, 5.11]
My computer monitor looks too bright 1.28 [0.44, 3.67]
I feel tired when doing work 2.08 [0.74, 5.84]
My neck shoulders, back and lower back hurt 0.52 [0.13, 2.09]
My fingers hurt 0.52 [0.07, 4.17]
I feel mentally stressed 1.30 [0.54, 3.14]
The suns glare affects my eyes when outdoors 1.37 [0.55, 3.40]
I find fluorescent office lighting
to be bothersome to my eyes
7.00 [0.88, 55.66]
RR, Risk Ratio.
©2017 The Authors Ophthalmic & Physiological Optics ©2017 The College of Optometrists
Ophthalmic & Physiological Optics 37 (2017) 644–654
651
J G Lawrenson et al. Blue-light blocking spectacle lenses
Given the role of blue light in the timing of the circadian
system, we examined evidence on the influence of blue-
blocking lenses on sleep quality. This outcome was reported
in two studies. Leung and co-workers
33
found no observed
difference in the effect of either low or high blue-blocking
lenses on the subjective assessment of sleep quality in nor-
mal participants. By contrast, Burkhart and Phelps
32
recruited participants reporting sleep difficulties who wore
either high or low blue-blocking lenses for three hours
prior to sleep for two weeks. High blue-blocking lenses
were associated with a statistically significant improvement
in self-reported sleep quality, based on a 10-point Likert
scale, for the high blue-blocking group compared to the
low blue-blocking lens group (MD =0.80 [0.17, 1.43]:
P=0.03).
No studies reporting on the effects of blue-blocking spec-
tacle lenses on macular health were identified. With the
widespread incorporation of backlit LED displays in mod-
ern digital devices, concerns have been raised regarding the
long-term safety of these screens, which have emission
peaks in the 460 nm to 490 nm spectral range. One of the
suggested benefits of blue-blocking spectacle lenses is to
protect the retina against these potentially damaging wave-
lengths. However, despite the perceived risks, the spectrally
weighted irradiance from these devices does not reach
international exposure limits, even for prolonged viewing.
Moreover, the emissions have been shown to be lower than
natural exposure from sunlight, even on a cloudy day in
winter, in the United Kingdom.
40
In summary, the findings of this systematic review indi-
cate that there is a lack of high quality clinical evidence for
a beneficial effect of blue-blocking spectacle lenses in the
general population to improve visual performance or sleep
quality, alleviate eye fatigue or conserve macular health.
Only three studies met our inclusion criteria and these were
generally poorly reported, with several limitations in study
design and/or implementation. All three included studies
were at risk of selection bias; differences in the appearance
of the lenses meant that it was impossible to fully mask par-
ticipants to the trial intervention; and we were unable to
exclude the possibility of selective outcome reporting. We
rated the overall certainty of the evidence using GRADE
20
as low or very low, and therefore we have little to no confi-
dence in the effect estimates. None of the included studies
reported on adverse effects associated with the use of blue-
blocking lenses.
There is a need for high quality studies to address the
effects of blue blocking spectacle lenses on visual perfor-
mance, and the potential alleviation of symptoms of eye-
strain and/or visual fatigue. There should be an agreed
standard set of outcomes, known as ‘core outcome sets’
(COS) as recommended by the COMET initiative.
41
These
sets could then be collected and reported to allow the
results of studies to be compared and combined as appro-
priate. The studies investigating these outcomes should
adopt a RCT design and be conducted on a general popu-
lation, using blue-blocking lenses with varying degrees of
blue light attenuation. Sampling could be stratified to
include participants varying in age, gender, ethnicity and
occupational or domestic exposure to blue light. Outcome
measures investigated in trials should include those that
are important to potential blue-blocking lens users (e.g.,
the maintenance of macular health and function, or allevi-
ation of digital eyestrain). Furthermore, attempts should
be made to mask participants and outcome assessors to
the intervention, to reduce the risk of performance bias.
Finally, given the importance of blue light for scotopic
sensitivity and in regulating the sleep-wake cycle, the
potential harms of blue-blocking spectacle lenses should
also be considered alongside the putative benefits of these
devices.
Acknowledgements
Funding: JGL and CCH received funding from the College
of Optometrists, UK for this review.
Disclosure
The authors report no proprietary interest in any of the
materials mentioned in this article. The lead reviewer (JL)
has given lectures on this topic at conferences for which
travel and accommodation has been paid by the organis-
ers. The other two authors (CH, LD) declare that they
have no known conflicts of interest related to the review
topic.
References
1. Noell WK, Walker VS, Kang BS & Berman S. Retinal dam-
age by light in rats. Invest Ophthalmol 1966; 5: 450–473.
2. Ham WT, Mueller HA, Ruffolo JJ Jr, Guerry D & Guerry
RK. Action spectrum for retinal injury from near-ultraviolet
radiation in the aphakic monkey. Am J Ophthalmol 1982;
93: 299–306.
3. Sparrow JR, Miller AS & Zhou J. Blue light-absorbing
intraocular lens and retinal pigment epithelium protection
in vitro. J Cataract Refract Surg 2004; 30: 873–878.
4. Davies S, Elliott MH, Floor E et al. Photocytotoxicity of
lipofuscin in human retinal pigment epithelial cells. Free
Radic Biol Med 2001; 31: 256–265.
5. Ham WT, Ruffolo JJ, Mueller HA, Clarke AM & Moon ME.
Histologic analysis of photochemical lesions produced in
rhesus retina by short-wave-length light. Invest Ophthalmol
Vis Sci 1978; 17: 1029–1035.
6. International Commission on Non-Ionizing Radiation Pro-
tection. ICNIRP guidelines on limits of exposure to
©2017 The Authors Ophthalmic & Physiological Optics ©2017 The College of Optometrists
Ophthalmic & Physiological Optics 37 (2017) 644–654
652
Blue-light blocking spectacle lenses J G Lawrenson et al.
incoherent visible and infrared radiation. Health Phys 2013;
105: 74–96.
7. Moon J, Yun J, Yoon YD et al. Blue light effect on retinal
pigment epithelial cells by display devices. Integr Biol
(Camb) 2017; 9: 436–443.
8. Tosini G, Ferguson I & Tsubota K. Effects of blue light on
the circadian system and eye physiology. Mol Vis 2016; 22:
61–72.
9. Downes SM. Ultraviolet or blue-filtering intraocular lenses:
what is the evidence? Eye (Lond) 2016; 30: 215–221.
10. Li X, Kelly D, Nolan JM, Dennison JL & Beatty S. The evi-
dence informing the surgeon’s selection of intraocular lens
on the basis of light transmittance properties. Eye (Lond)
2017; 31: 258–272.
11. Mainster MA & Sparrow JR. How much blue light
should an IOL transmit? Br J Ophthalmol 2003; 87:
1523–1529.
12. Downie L, Busija L & Keller P. Blue-light filtering intraocu-
lar lenses (IOLs) for protectiong macular health. Cochrane
Database Syst Rev 2015;11:CD11977.
13. Cuthbertson FM, Peirson SN, Wulff K, Foster RG & Downes
SM. Blue light-filtering intraocular lenses: review of poten-
tial benefits and side effects. J Cataract Refract Surg 2009; 35:
1281–1297.
14. Do MT & Yau KW. Intrinsically photosensitive retinal
ganglion cells. Physiol Rev 2010; 90: 1547–1581.
15. Boulton M, R
ozanowska M & R
ozanowski B. Retinal photo-
damage. J Photochem Photobiol B. 2001; 64: 144–61.
16. Ayaki M, Hattori A, Maruyama Y et al. Protective effect of
blue-light shield eyewear for adults against light pollution
from self-luminous devices used at night. Chronobiol Int
2016; 33: 134–139.
17. Ide T, Toda I, Miki E & Tsubota K. Effect of blue light-
reducing eye glasses on critical flicker frequency. Asia Pac J
Ophthalmol (Phila) 2015; 4: 80–85.
18. Review Manager (RevMan) [Computer program]. Version
5.3. Copenhagen. The Nordic Cochrane Centre: The
Cochrane Collaboration, 2014.
19. Higgins JPT, Altman DG & Sterne JAC (editors). Chapter 8:
Assessing risk of bias in included studies. In: Higgins JPT,
Churchill R, Chandler J, Cumpston MS (editors), Cochrane
Handbook for Systematic Reviews of Interventions version
5.2.0 (updated June 2017) Cochrane, 2017; Available from
www.training.cochrane.org/handbook.
20. Guyatt GH, Oxman AD, Vist GE et al. GRADE: an emerging
consensus on rating quality of evidence and strength of rec-
ommendations. BMJ 2008; 336: 924–926.
21. Figueiro M & Rea MS. The impact of self-luminous displays
on evening melatonin levels. 27th Annual Meeting of the
Associated Professional Sleep Societies, LLC. Sleep 2013; 36
(Abstract Supplement): A184.
22. Figueiro MG, Wood B, Plitnick B & Rea MS. The
impact of light from computer monitors on melatonin
levels in college students. Neuro Endocrinol Lett 2011;
32: 158–163.
23. Hovis JK, Lovasik JV, Cullen AP & Kothe AC. Physical char-
acteristics and perceptual effects of “blue-blocking” lenses.
Optom Vis Sci 1989; 66: 682–689.
24. Kaido M, Toda I, Oobayashi T, Kawashima M, Katada Y
& Tsubota K. Reducing short-wavelength blue light in
dry eye patients with unstable tear film improves perfor-
mance on tests of visual acuity. PLoS ONE 2016; 11:
e0152936.
25. Lee JE, Stein JJ, Prevor MB et al. Effect of variable tinted
spectacle lenses on visual performance in control subjects.
CLAO J 2002; 28: 80–82.
26. Luria SM. Vision with chromatic filters. Am J Optom Arch
Am Acad Optom 1972; 49: 818–829.
27. Sasseville A, Paquet N, Sevigny J & Hebert M. Blue blocker
glasses impede the capacity of bright light to suppress mela-
tonin production. J Pineal Res 2006; 41: 73–78.
28. Thomas SR & Kuyk TK. D-15 performance with short wave-
length absorbing filters in normals. Am J Optom Physiol Opt
1988; 65: 697–702.
29. van der Lely S, Frey S, Garbazza C et al. Blue blocker glasses
as a countermeasure for alerting effects of evening light-
emitting diode screen exposure in male teenagers. J Adolesc
Health 2015; 56: 113–119.
30. Wood B, Rea MS, Plitnick B & Figueiro MG. Light level and
duration of exposure determine the impact of self-luminous
tablets on melatonin suppression. Appl Ergon 2013; 44: 237–
240.
31. Hammond BR. Attenuating Photostress and glare disability
in pseudophakic patients through the addition of a short-
wave absorbing filter. J Ophthalmol 2015; 2015: 607–635.
32. Burkhart K & Phelps JR. Amber lenses to block blue light
and improve sleep: a randomized trial. Chronobiol Int 2009;
26: 1602–1612.
33. Leung TW, Li RW & Kee CS. Blue-light filtering spectacle
lenses: optical and clinical performances. PLoS ONE 2017;
12: e0169114.
34. Lin JB, Gerratt BW, Bassi CJ & Apte RS. Short-wavelength
light-blocking eyeglasses attenuate symptoms of eye fatigue.
Invest Ophthalmol Vis Sci 2017; 58: 442–447.
35. Armstrong RA. When to use the Bonferroni correction.
Ophthalmic Physiol Opt 2014; 34: 502–508.
36. Benedetto S, Drai-Zerbib V, Pedrotti M, Tissier G & Baccino
T. E-readers and visual fatigue. PLoS ONE 2013; 8: e83676.
37. Rosenfield M. Computer vision syndrome: a review of ocu-
lar causes and potential treatments. Ophthalmic Physiol Opt
2011; 31: 502–515.
38. Gowrisankaran S & Sheedy JE. Computer vision syndrome:
a review. Work 2015; 52: 303–314.
39. Zhu XF, Zou HD, Yu YF, Sun Q & Zhao NQ. Compar-
ison of blue light-filtering IOLs and UV light-filtering
IOLs for cataract surgery: a meta-analysis. PLoS ONE
2012; 7: e33013.
40. O’Hagan JB, Khazova M & Price LL. Low-energy light bulbs,
computers, tablets and the blue light hazard. Eye (Lond)
2016; 30: 230–233.
©2017 The Authors Ophthalmic & Physiological Optics ©2017 The College of Optometrists
Ophthalmic & Physiological Optics 37 (2017) 644–654
653
J G Lawrenson et al. Blue-light blocking spectacle lenses
41. Williamson PR, Altman DG, Bagley H et al. The COMET
Handbook: version 1.0. Trials 2017; 18(Suppl 3): 280.
Supporting Information
Additional Supporting Information may be found in the
online version of this article:
File S1. Ovid MEDLINE search strategy
File S2. Excluded Studies.
File S3. Characteristics of Included Studies.
Professor John G Lawrenson studied optometry at Aston University, Birmingham. Following a pre-
registration year at Moorfields Eye Hospital London, he undertook postgraduate research at City
University, leading to a PhD in Visual Science. He then carried out a post-doctoral research fellowship
in neuroscience at University College London, before returning to join the academic staff at City
University, where he currently holds a chair in Clinical Visual Science. Professor Lawrenson’s is an
advocate for evidence-based clinical practice and holds a Master’s degree in Evidence-based Healthcare
from the University of Oxford. His primary research interests lie in the field of age-related eye disease;
particularly glaucoma and age-related macular degeneration. He is an Editor for the Cochrane Eyes
and Vision Group and has authored several Cochrane Systematic Reviews.
Professor Christopher C Hull originally studied applied physics prior to spending two years working in
the defence industry on the optics and vision of aircraft displays and sighting systems. Following a PhD
in applied optics at Imperial College London, he moved to the Department of Optometry and Visual
Science at City where he currently holds a chair in optics of vision and is Associate Dean for Research
and Enterprise for the School of Health Sciences having previously been head of optometry for eight
years. His main interests are in how the optical image interacts with vision and in particular the effects
of cornea and lens on the optical image following refractive surgery. Current work centres on intraocu-
lar lenses and their complications as well as artificial corneas. His interest in the adverse effects of light
on vision started with work on the blue light output from projectors used in interactive whiteboards
some 12 years ago.
Dr Laura E Downie is a Senior Lecturer and a recent National Health and Medical Research Council
(NHMRC) Translating Research Into Practice Fellow in the Department of Optometry and Vision Sci-
ences at the University of Melbourne, Victoria, Australia. She completed her undergraduate optometry
degree (2003) and doctorate (2008) at the University of Melbourne. In her current role, she provides
didactic and clinical training to Doctor of Optometry students, leads the specialty Cornea clinic at
University of Melbourne eye care clinic and heads the Downie Laboratory: Anterior Eye, Clinical Trials
and Research Translation Unit. A major component of her research focuses upon the translation of evi-
dence into practice in the context of eye health, including the role of diet and nutritional supplementa-
tion as modifiable risk factors for sight-threatening conditions, such as age-related macular
degeneration. In 2014, she was awarded two prestigious fellowships from the NHMRC and achieved
international recognition for her research as recipient of the Irvin and Beatrice Borish Award from the
American Academy of Optometry.
©2017 The Authors Ophthalmic & Physiological Optics ©2017 The College of Optometrists
Ophthalmic & Physiological Optics 37 (2017) 644–654
654
Blue-light blocking spectacle lenses J G Lawrenson et al.
