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The impact of blue light on the
eye has gained increased inter-
est in recent years due to the
explosion of devices and light-
ing sources emitting wavelengths
between 400nm and 500nm.1,2 Gen-
eral lighting, desktop computers,
laptops, tablets, electronic reading
devices and smartphones all expose
the eye to blue light. Nevertheless,
clinicians must remember that the
amount of light emanating from
artificial sources is a fraction of the
radiation emitted from the sun—a
typical LED used for general light-
ing emits around 50 to 70 lux, while
sunlight provides approximately
100,000 lux.3
The Real Risk
A number of ocular conditions are
associated with blue light exposure
(Table 1). However, due to the prox-
imity within the electromagnetic
spectrum of blue and ultra-violet
(UV) radiation, it is unclear precisely
which are the damaging wave-
lengths. Given that UV exposure
is associated with eyelid
malignancies such as basal
cell and squamous cell
carcinomas, photokeratitis,
pterygia and cortical cata-
racts, researchers speculate
this may be the damaging
radiation rather than vis-
ible blue light.4 While the
cornea, aqueous and vitre-
ous are largely transparent
to wavelengths between 300nm and
400nm, the natural crystalline lens
absorbs much of the ultraviolet A
(UVA) range (320nm to 400nm),
thereby shielding the retina from its
potentially toxic effects.5
No clear answer exists as to what
constitutes excessive exposure.
Single, high amounts are damaging,
but so may be long-term, low level
exposure to both the eyes and skin.
For example, UVA radiation dam-
ages keratinocytes in the basal layer
of the epidermis, which is the site
of most skin cancers. Ultraviolet B
(UVB, 290nm to 320nm) exposure
can lead to sunburn, photokeratitis,
cataracts and retinal lesions. This
wavelength tends to damage the
skin’s superficial epidermal layers
and plays a key role in the develop-
ment of skin cancer, as well as a
contributory role in tanning and
For radiation to damage the pos-
terior segment of the eye, it must
be transmitted through the ocular
media. While most blue light does
reach the retina of a young healthy
eye, the natural yellowing of the
crystalline lens with increasing age
creates a blue-blocking filter, thereby
obstructing passage of these wave-
lengths. But even the clear crystal-
Blue Light
The sun is your biggest enemy, and digital devices aren’t as bad as you think.
Here’s the current research and recommendations.
By Mark Rosenfield, MCOptom, PhD
Living With Blue
Light Exposure
Table 1. Ocular Conditions Associated
With Blue Light Exposure
Age-related macular degeneration
Basal cell and squamous cell carcinomas
Cortical cataract
Damage to the retinal pigment epithelium
Eye strain during and after sustained near-work
line lens absorbs some wavelengths
between 400nm and 420nm.6 Addi-
tionally, retinal illuminance will be
reduced further by the pupil, given
that pupillary constriction is greater
when the eye is exposed to blue light
compared with an equal amount of
green light.7
The photoreceptors within the
macula are directly exposed to
light, as they have no other cell
layers covering them. Within these
photoreceptors, the antioxidative
pigments lutein and zeaxanthin
normally filter out blue light due to
their yellow color. The xanthophylls
have a protective role against retinal
oxidation through the absorption
of damaging blue light, neutraliza-
tion of photosensitizers and reactive
oxygen species, and scavenging of
free radicals.8,9 These antioxidants
are obtained from the diet and have
been included in the AREDS-2 for-
mulation designed for the prevention
of age-related macular degenera-
Although a number of animal
studies show direct evidence of
retinal damage following blue light
exposure, almost all of them used
radiation levels far in excess of natu-
ral conditions.11,12 Blue light damage
has been observed following both
in vitro and in vivo studies.13-16 One
investigation observed a significant
loss of photoreceptors in the supe-
rior retina of albino rats following
24 hours of exposure to LED light
sources at 6,000 lux through a
dilated pupil.11 In contrast, cyclic
exposure (12 hours on/12 hours
off) to LED light sources at 500
lux without pupil dilation for one
month did not produce any signifi-
cant retinal cell loss in pigmented
(non-albino) rats.11 Additionally,
significant retinal damage was
observed when albino mice were
continuously exposed to white light
of high intensity (5,000 lux) for
seven days.12 Given the
extremely high levels of
radiation necessary to pro-
duce retinal damage, natu-
ralistic exposure levels are
unlikely to be large enough
to cause significant tissue
Digital Eye Strain
We currently live in a
society where electronic
devices are deeply embed-
ded into daily life. Ninety
percent of families in the
United States own at least
one computer, smartphone
or tablet, while the typical
American family has five
or more of these devices.17
Furthermore, between
40% and 60% of individuals expe-
rience visual or ocular symptoms
while viewing electronic displays
for prolonged periods of time.18,19
These symptoms—including eye
fatigue, ocular irritation, burning,
eye strain, redness, dryness, blurred
or double vision—are collectively
termed digital eye strain (DES).20
Although the symptoms are typically
transient and disappear soon after
device use ceases, some individuals
do experience ocular discomfort for
a sustained period after prolonged
viewing of an electronic screen.
Many have speculated that the
high levels of blue light emitted
from digital displays may be respon-
sible for the development of DES
symptoms. For example, blue light
contributes more than one-third of
the emission spectrum of an Apple
iPhone 7.21 However, the evidence to
support this association is minimal.
Nevertheless, many ophthalmic lens
manufacturers market blue-blocking
filters as a treatment paradigm
for DES. One study examined the
effect of low-, medium- and high-
density blue filters (in the form of
wraparound goggles) worn during
computer work in groups of dry eye
and normal subjects.22 The research-
ers observed a significant reduction
in symptoms in the dry eye group,
but not in the non-dry eye subjects,
for all of the filter densities tested.
However, the study did not include a
control condition, and so a placebo
effect cannot be ruled out. Further,
the wraparound goggles may have
reduced tear evaporation in the dry
eye subjects, thus increasing ocular
Subsequently, other investigators
evaluated the effect of blue-blocking
lenses on both symptoms of DES
and the critical fusion frequency
(a parameter previously associated
with eye fatigue) following a two-
hour computer task.23-25 The authors
determined that the high-blocking
filter, which blocked around 60%
of the blue light, produced a signifi-
cantly greater post-task change in
critical fusion frequency compared
with either a low-blocking blue
filter (which blocked approxi-
mately 24%) or control lenses that
blocked approximately 3.2% of blue
Fig. 1. Appearance of the computer screen when
viewed through either a filter that blocked 99%
of blue light (right) or an equiluminant 0.3log
unit neutral density filter (left). This image, which
shows the bright yellow appearance of the blue-
blocking filter, is for illustrative purposes only. In the
study, only one of the filters was present for each
experimental trial.26
light. Based on the critical fusion
frequency findings, the authors
reported that subjects wearing high-
blocking filters had less fatigue after
the two-hour task than before they
started the trial. As for subjective
symptoms, the high-blocking filters
produced a significant reduction in
pain, heaviness and itchy eyes, but
not in other previously noted DES
symptoms such as eye fatigue.20
However, the various filter condi-
tions were performed on different
groups, and so the reduced symp-
toms observed in the high-blocking
filter group may have been a conse-
quence of those particu-
lar individuals, rather
than the effect of the
Two studies from
our laboratory do not
support the proposal
that DES symptoms
are associated with
exposure to visible
blue light. In the first
investigation, we com-
pared symptoms after
sustained reading from
a tablet computer.26
The screen was covered
either with a filter that
blocked more than
99% of blue light, or
an equiluminant, neutral-density
filter (Figure 1). We observed no
significant difference in post-task
symptoms between the two condi-
tions (Figure 2). The study does have
some limitations, as it was not per-
formed on a double-blind basis, and
most commercially available filters
only block between 10% and 20%
of blue light, rather than the 99%
level tested here.27
Therefore, in a subsequent inves-
tigation, we compared three com-
mercially available lenses having an
identical, clear appearance using a
double-blind protocol. Twenty-four
subjects performed a 20-minute
reading task using a tablet computer
while wearing lenses containing
either a blue-blocking filter (TheraB-
lue 1.67 or TheraBlue polycarbon-
ate) or a CR-39 control lens.28 While
we observed a significant increase
in symptoms immediately following
the near vision task, no significant
difference in symptoms was found
between the three lens conditions
(Figure 3).
Accordingly, there is little evidence
at this time to support the use of
blue-blocking filters as a clinical
treatment for DES. Management of
other ocular factors, as well as the
creation of an optimal environment
for screen viewing, are more likely to
provide greater success in minimiz-
ing symptoms. For instance, most
smartphones now include a night
setting that reduces the magnitude
of short wavelengths emitted from
the screen. While this shift is unlikely
to reduce DES symptoms, it may
attenuate any difficulty in falling
asleep after sustained viewing of
digital screens.
Circadian Rhythm
Blue light exposure can affect the
physiological circadian rhythm.
The natural sleep-wake cycle is
controlled by the release of the hor-
Fig. 2. Mean total symptom scores for the blue-blocking (BB) and neutral density
(ND), i.e., control conditions immediately following a 30-minute reading task from a
tablet. Error bars indicate one standard error of the mean. No significant difference in
symptoms was observed for these two conditions.26
Intraocular Lenses
If the natural lens is removed surgically (e.g., cataract
extraction), the question arises whether it should be
replaced with a clear or yellow (i.e., blue-blocking) intra-
ocular lens (IOL). A Cochrane systematic review on the
effect of blue-filtering IOLs noted that a yellow IOL does
not produce any significant reduction in either best-cor-
rected visual acuity or contrast sensitivity.1 However, the
same review also reported no significant difference in the
proportion of eyes that went on to develop late-stage age-
related macular degeneration (AMD) after three years of
follow-up, or any stage of AMD after one year of follow-up.
The authors concluded that the use of blue-blocking IOLs
to alter the risk of developing AMD is “speculative.”1
1. Downie LE, Busija L, Keller PR. Blue-light filtering intraocular lenses (IOLs) for pro-
tecting macular health. Cochrane Database of Syst Rev. 2015;11:CD011977.
Blue Light
mone melatonin from the pineal
gland.29 Typically, melatonin secre-
tion increases soon after the onset
of darkness, peaks in the middle
of the night (between 2am and
4am) and gradually falls during the
second half of the night. Exposure
to any visible light, but especially
blue light, suppresses the secretion
of melatonin. When comparing the
effects of 6.5 hours of blue light
exposure to green light of compa-
rable brightness, the blue light sup-
pressed melatonin for about twice
as long, and doubled the shift in
circadian rhythms (three hours vs.
1.5 hours).30
Exposure to blue light sources in
the evening will affect one’s ability
to fall asleep. Subjects reading from
an electronic reader take longer to
fall asleep and have reduced evening
sleepiness, reduced melatonin secre-
tion, later timing of their circadian
clock and reduced morning alertness
when compared with subjects who
read a printed book.31 Similarly, the
use of short wavelength-blocking
glasses at night increases both sub-
jectively measured sleep quality and
duration.32,33 Therefore, clinicians
should recommend patients avoid
using electronic digital devices for
two to three hours before bedtime.
However, blue light exposure isn’t
always a bad thing. Evidence shows
that the use of blue-enriched, white
fluorescent lighting (17,000K) in an
office setting improved alertness,
positive mood, ability to concen-
trate, ability to think clearly and
decreased evening fatigue, when
compared with white fluorescent
lighting (4,000K).34
How Much is Too Much?
In evaluating safe levels of blue light,
the International Commission on
Non-Ionizing Radiation Protection
(ICNIRP) provided guideline levels
below which adverse health effects
were considered unlikely. Their rec-
ommendations state that detailed
assessments of white light sources
were not required for luminance val-
ues below 104cd/m2.35
Applying this criterion to every-
day conditions, staring at the sky in
the United Kingdom on a clear day
in June or a cloudy day in December
represents about 10.4% and 3.4%,
respectively, of this standard. The
emission of blue light from digital
displays barely reaches 4% of this
limit (Table 2). Thus, it may be
concluded that the magnitude of
exposure from digital devices does
not approach dangerous levels.35
Interestingly, a new policy on out-
door light pollution, recently issued
by the government of France, spe-
cifically restricts the emission of blue
light. The decree requires that, in all
instances, the correlated color tem-
perature of light should not exceed
3,000 degrees Kelvin (equivalent
to that of a tungsten halogen light
Real-world Recommendations
By far the largest source of low
wavelength radiation comes from
sunlight, and it is a risk factor for
age-related macular degeneration,
carcinoma, photokeratitis, pterygia,
cataract and retinal pigment epithe-
lium damage.37 Patients with high
exposure to sunlight need to be
counseled on the use of visors and
brimmed headwear, UV-blocking
lenses with a wrap-around design,
small vertex distances and lenses
that cover a large area. While lenses
may block eye exposure to danger-
ous wavelengths, the skin (including
the eyelids) may still be exposed.
Additionally, blue light’s effect on
the body’s circadian rhythm can
interfere with sleep patterns, and
exposure should be minimized
two to three hours before bedtime.
However, minimal evidence supports
Fig. 3. Mean post-task change in symptom score following a 20-minute reading task
from a tablet for three lens conditions. CR-39 = clear lens with no blue-blocking
filter. Both the polycarbonate (poly) and 1.67 Therablue lenses included a clear,
commercially available blue-blocking filter. Error bars indicate one standard error
of the mean. No significant difference in symptoms was observed for these two
Table 2. Range of Digital Device
Blue Light Exposure.35
Type of Device % of ICNIRP limit
Desktop 0.71 - 1.26
Laptop 0.63 - 1.97
Tablet 0.43 – 2.38
Smartphone 1.78 – 4.09
the use of blue-blocking filters as a
treatment for DES and they are not
necessary for the majority of indi-
viduals. n
Dr. Rosenfield is a professor at
SUNY College of Optometry.
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Blue Light
ResearchGate has not been able to resolve any citations for this publication.
Full-text available
Light causes damage to the retina (phototoxicity) and decreases photoreceptor responses to light. The most harmful component of visible light is the blue wavelength (400–500 nm). Different filters have been tested, but so far all of them allow passing a lot of this wavelength (70%). The aim of this work has been to prove that a filter that removes 94% of the blue component may protect the function and morphology of the retina significantly. Three experimental groups were designed. The first group was unexposed to light, the second one was exposed and the third one was exposed and protected by a blue-blocking filter. Light damage was induced in young albino mice (p30) by exposing them to white light of high intensity (5,000 lux) continuously for 7 days. Short wavelength light filters were used for light protection. The blue component was removed (94%) from the light source by our filter. Electroretinographical recordings were performed before and after light damage. Changes in retinal structure were studied using immunohistochemistry, and TUNEL labeling. Also, cells in the outer nuclear layer were counted and compared among the three different groups. Functional visual responses were significantly more conserved in protected animals (with the blue-blocking filter) than in unprotected animals. Also, retinal structure was better kept and photoreceptor survival was greater in protected animals, these differences were significant in central areas of the retina. Still, functional and morphological responses were significantly lower in protected than in unexposed groups. In conclusion, this blue-blocking filter decreases significantly photoreceptor damage after exposure to high intensity light. Actually, our eyes are exposed for a very long time to high levels of blue light (screens, artificial light LED, neons…). The potential damage caused by blue light can be palliated.
Full-text available
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 phototoxicity. 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 measured 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 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-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 spectacle lenses for the general population to improve visual performance or sleep quality, alleviate eye fatigue or conserve macular health.
Full-text available
Purpose: The purpose of this study was to determine whether subjects who wear short wavelength-blocking eyeglasses during computer tasks exhibit less visual fatigue and report fewer symptoms of visual discomfort than subjects wearing eyeglasses with clear lenses. Methods: A total of 36 healthy subjects (20 male; 16 female) was randomized to wearing no-block, low-blocking, or high-blocking eyeglasses while performing a 2-hour computer task. A masked grader measured critical flicker fusion frequency (CFF) as a metric of eye fatigue and evaluated symptoms of eye strain with a 15-item questionnaire before and after computer use. Results: We found that the change in CFF after the computer task was significantly more positive (i.e., less eye fatigue) in the high-block versus the no-block (P = 0.027) and low-block (P = 0.008) groups. Moreover, random assignment to the high-block group but not to the low-block group predicted a more positive change in CFF (i.e., less eye fatigue) following the computer task (adjusted β = 2.310; P = 0.002). Additionally, subjects wearing high-blocking eyeglasses reported significantly less feeling pain around/inside the eye (P = 0.0063), less feeling that the eyes were heavy (P = 0.0189), and less feeling that the eyes were itchy (P = 0.0043) following the computer task, when compared to subjects not wearing high-blocking lenses. Conclusions: Our results support the hypothesis that short-wavelength light-blocking eyeglasses may reduce eye strain associated with computer use based on a physiologic correlate of eye fatigue and on subjects' reporting of symptoms typically associated with eye strain.
Full-text available
Purposes: To evaluate the optical performance of blue-light filtering spectacle lenses and investigate whether a reduction in blue light transmission affects visual performance and sleep quality. Methods: Experiment 1: The relative changes in phototoxicity, scotopic sensitivity, and melatonin suppression of five blue-light filtering plano spectacle lenses were calculated based on their spectral transmittances measured by a spectrophotometer. Experiment 2: A pseudo-randomized controlled study was conducted to evaluate the clinical performance of two blue-light filtering spectacle lenses (BF: blue-filtering anti-reflection coating; BT: brown-tinted) with a regular clear lens (AR) serving as a control. A total of eighty computer users were recruited from two age cohorts (young adults: 18-30 yrs, middle-aged adults: 40-55 yrs). Contrast sensitivity under standard and glare conditions, and colour discrimination were measured using standard clinical tests. After one month of lens wear, subjective ratings of lens performance were collected by questionnaire. Results: All tested blue-light filtering spectacle lenses theoretically reduced the calculated phototoxicity by 10.6% to 23.6%. Although use of the blue-light filters also decreased scotopic sensitivity by 2.4% to 9.6%, and melatonin suppression by 5.8% to 15.0%, over 70% of the participants could not detect these optical changes. Our clinical tests revealed no significant decrease in contrast sensitivity either with (95% confidence intervals [CI]: AR-BT [-0.05, 0.05]; AR-BF [-0.05, 0.06]; BT-BF [-0.06, 0.06]) or without glare (95% CI: AR-BT [-0.01, 0.03]; AR-BF [-0.01, 0.03]; BT-BF [-0.02, 0.02]) and colour discrimination (95% CI: AR-BT [-9.07, 1.02]; AR-BF [-7.06, 4.46]; BT-BF [-3.12, 8.57]). Conclusion: Blue-light filtering spectacle lenses can partially filter high-energy short-wavelength light without substantially degrading visual performance and sleep quality. These lenses may serve as a supplementary option for protecting the retina from potential blue-light hazard. Trial registration: NCT02821403.
Full-text available
To save energy, the European directives from the Eco-design of Energy Using Products (2005/32/CE) has recommended the replacement of incandescent lamps by more economic devices such as Light Emitting Diodes (LEDs). However, the emission spectrum of these devices is enriched in blue radiations, known to be potentially dangerous to the retina. Recent studies showed that light exposure contribute to the onset of early stages of Age related macular degeneration (AMD). Here, we investigate, in albinos and pigmented rats, the effects of different exposure protocols. Twenty-four hours exposure at high luminance was compared to a cyclic (dark/light) exposure at domestic levels for 1 week and 1 month, using different LEDs (Cold-white, blue and green), as well as fluorocompacts bulbs and fluorescent tubes.The data suggest that the blue component of the white-LED may cause retinal toxicity at occupational domestic illuminance and not only in extreme experimental conditions, as previously reported. It is important to note that the current regulations and standards have been established on the basis of acute light exposure and do not take into account the effects of repeated exposure.
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Computer vision syndrome, also known as digital eye strain, is the combination of eye and vision problems associated with the use of computers (including desktop, laptop and tablets) and other electronic displays (eg smartphones and electronic reading devices). In today's world, the viewing of digital screens for both vocational and avocational activities is virtually universal. Digital electronic displays differ significantly from printed materials in terms of the within-task symptoms experienced. Many individuals spend 10 or more hours per day viewing these displays, frequently without adequate breaks. In addition, the small size of some portable screens may necessitate reduced font sizes, leading to closer viewing distances, which will increase the demands on both accommodation and vergence. Differences in blink patterns between hardcopy and electronic displays have also been observed. Digital eye strain has been shown to have a significant impact on both visual comfort and occupational productivity, since around 40% of adults and up to 80% of teenagers may experience significant visual symptoms (principally eye strain, tired and dry eyes), both during and immediately after viewing electronic displays. This paper reviews the principal ocular causes for this condition, and discusses how the standard eye examination should be modified to meet today's visual demands. It is incumbent upon all eye care practitioners to have a good understanding of the symptoms associated with, and the physiology underlying problems while viewing digital displays. As modern society continues to move towards even greater use of electronic devices for both work and leisure activities, an inability to satisfy these visual requirements will present significant lifestyle difficulties for patients.
Background: Many ophthalmic lens manufacturers are currently marketing blue-blocking filters, which they claim will reduce symptoms of Digital Eye Strain (DES). However, there is limited evidence to support the proposal that DES results from the blue light emitted by electronic screens. Objective: This investigation compared the effect of blue-blocking filters on DES symptoms with a no-filter lens, using a double-blind methodology. Methods: 24 subjects were required to perform a 20-minute reading task from a tablet computer. They wore either lenses containing a blue-blocking filter (TheraBlue 1.67 or TheraBlue polycarbonate) or a CR-39 control lens which did not include a filter. Immediately following each session, subjects completed a questionnaire to quantify symptoms of DES. Results: While a significant increase in symptoms was observed immediately following the near vision task (p = 0.00001), no significant difference in symptoms was found between the 3 lens conditions (p = 0.74). Conclusions: There is little evidence at this time to support the use of blue-blocking filters as a clinical treatment for DES. Management of other ocular factors, as well as the creation of an optimal environment for screen viewing, are more likely to provide greater success in minimizing symptoms.
Significance: Many manufacturers are currently marketing blue-blocking (BB) filters, which they claim will reduce the symptoms of digital eyestrain (DES). However, there is limited evidence to support the proposal that DES results from the blue light emitted by these devices. Purpose: The visual and ocular symptoms commonly experienced when viewing digital screens are collectively termed DES. The emission spectrum of modern digital displays frequently includes a high percentage of blue light. Being higher in energy, these short wavelengths may contribute to DES. This study examined the effect of a BB filter on symptoms of DES during a sustained near-vision task. Methods: Twenty-three young, visually normal subjects were required to perform a 30-minute reading task from a tablet computer. The digital screen was overlaid with either a BB or neutral-density (ND) filter producing equal screen luminance. During each session, the accommodative response, pupil diameter, and vertical palpebral aperture dimension were measured at 0, 9, 19, and 29 minutes after the start of the reading task. Immediately following each session, subjects completed a questionnaire to quantify symptoms of DES. Results: The BB filter blocked 99% of the wavelengths between 400 and 500 nm. The mean total symptom scores (±1 SEM) for the BB and ND filter conditions were 42.83 (3.58) and 42.61 (3.17), respectively (P = .62). No significant differences in accommodation or vertical palpebral aperture dimension were observed between the two filter conditions, although the magnitude of the mean accommodative response did increase significantly during the first 9 minutes of the task (P = .02). Conclusions: A filter that eliminated 99% of the emitted blue light was no more effective at reducing symptoms of DES than an equiluminant ND filter. There is little evidence at this time to support the use of BB filters to minimize near work-induced asthenopia.
Purpose: Exposure to increasing amounts of artificial light during the night may contribute to the high prevalence of reported sleep dysfunction. Release of the sleep hormone melatonin is mediated by the intrinsically photosensitive retinal ganglion cells (ipRGCs). This study sought to investigate whether melatonin level and sleep quality can be modulated by decreasing night-time input to the ipRGCs. Methods: Subjects (ages 17-42, n = 21) wore short wavelength-blocking glasses prior to bedtime for 2 weeks. The ipRGC-mediated post illumination pupil response was measured before and after the experimental period. Stimulation was presented with a ganzfeld stimulator, including one-second and five-seconds of long and short wavelength light, and the pupil was imaged with an infrared camera. Pupil diameter was measured before, during and for 60 s following stimulation, and the six-second and 30 s post illumination pupil response and area under the curve following light offset were determined. Subjects wore an actigraph device for objective measurements of activity, light exposure, and sleep. Saliva samples were collected to assess melatonin content. The Pittsburgh Sleep Quality Index (PSQI) was administered to assess subjective sleep quality. Results: Subjects wore the blue-blocking glasses 3:57 ± 1:03 h each night. After the experimental period, the pupil showed a slower redilation phase, resulting in a significantly increased 30 s post illumination pupil response to one-second short wavelength light, and decreased area under the curve for one and five-second short wavelength light, when measured at the same time of day as baseline. Night time melatonin increased from 16.1 ± 7.5 pg mL(-1) to 25.5 ± 10.7 pg mL(-1) (P < 0.01). Objectively measured sleep duration increased 24 min, from 408.7 ± 44.9 to 431.5 ± 42.9 min (P < 0.001). Mean PSQI score improved from 5.6 ± 2.9 to 3.0 ± 2.2. Conclusions: The use of short wavelength-blocking glasses at night increased subjectively measured sleep quality and objectively measured melatonin levels and sleep duration, presumably as a result of decreased night-time stimulation of ipRGCs. Alterations in the ipRGC-driven pupil response suggest a shift in circadian phase. Results suggest that minimising short wavelength light following sunset may help in regulating sleep patterns.