New findings from a meta-analysis published in the Cochrane Database of Systematic Reviews suggest that the use of blue-light glasses may not be as visually beneficial as originally thought.
Give me some background first.
Blue-light filtering or blocking spectacle lenses are designed to filter ultraviolet radiation and short-wavelength visible light from the eye’s reach.
In fact, prior research concluded that such blue light glasses improved sleeping patterns, helped with computer vision syndrome (including dry eye), blurred vision, headaches and eye strain (due to extended digital device usage) as well as reduced eye fatigue.
And this new study contradicts that?
According to researchers, yes.
Investigators at the University of Melbourne, City University of London, and Monash University, sought to evaluate the effects of blue-light filtering lenses vs non-blue-light filtering lenses when used for visual performance improvement, improving sleep quality, and providing macular protection in adult patients.
How’d they do it?
The researchers searched seven electronic databases of clinical trials—including the Cochrane Central Register of Controlled Trials (CENTRAL) and ClincialTrials.gov—that included randomized controlled trials (CRTs) of participants where both blue-light and non-blue light filtering lenses were used.
How many trials did they identify?
A total of seven RCTs from six countries were selected, with sample sizes ranging from five to 156 participants and interventional follow-up periods from less than one day to 5 weeks.
An estimated 50% of the RCTs were designed as a parallel-arm while the other half featured cross-over designs.
What data was collected?
The primary outcome included changes in visual fatigue score and critical flicker-fusion frequency (CFF) between baseline and follow-up (one month).
Secondary outcomes were:
- Best-corrected visual acuity (BCVA)
- Contrast sensitivity
- Discomfort glare
- Proportion of eyes with pathological macular finding
- Color discrimination
- Patients with reduced daytime alertness
- Serum melatonin levels
- Subjective sleep quality
- Satisfaction with visual performance
All findings were assessed in relation to both ocular and systemic adverse effects, according to the researchers.
And the findings?
Per the review, no difference or little to no difference between lenses was noted for subjective visual fatigue scores (at less than one week of follow-up with low-certainty evidence).
Number-wise, one RCT with 120 participants noted that there was no difference between intervention arms reported a mean difference (MD) of 9.76 units (indicating worsening of symptoms) with a 95% confidence interval (CI) -33.95 to 53.47.
What about CFF?
Researchers reported little to no difference in CFF between lenses for the same time-frame period, with one study showing no significant difference between intervention arms (MD ‐ 1.13 Hz lower (indicating poorer performance), 95% CI ‐ 3.00 to 0.74; 120 participants)
And visual performance?
A probable little or no effect on BCVA was found between both lenses (MD 0.00 logMAR units, 95% CI ‐0.02 to 0.02; 1 study, 156 participants; moderate‐certainty evidence), according to one study.
However, researchers also noted a lack of available data and the small number of studies when reporting these results.
What about sleep?
According to the study authors, inconsistent findings were discovered across a number of RCTs for sleep quality, with some showing sleep score improvements for blue-light filtering lenses and others finding no significant difference.
They attributed this determination to a lack of quantitative data and differences in the study population sizes.
Any common adverse effects?
Yes, but not consistently, the investigators found.
Varying and infrequent adverse effects (AEs) relating to blue-light filtering lenses across the 17 RCTs included:
- Depressive symptoms
- Headache
- Discomfort wearing glasses
- Lower mood
AEs associated with non-blue-light filtering lenses were hyperthymia (occasional) and discomfort while wearing the spectacles.
And the other measured outcomes?
The study authors were unable to report findings,“as none of the studies evaluated these outcomes”—a significant limitation to the review.
“The short follow-up period also affected our ability to consider potential longer-term outcomes,” stated senior author Laura Downie, head of the Downie Laboratory: Anterior Eye, Clinical Trials and Research Translation Unit, at the University of Melbourne, Victoria, Australia.
What did the authors have to say about this?
Per Downie, no short-term advantages for visual fatigue were associated with blue-light filtering lenses vs non-blue light. “It is also currently unclear whether these lenses affect vision quality or sleep-related outcomes, and no conclusions could be drawn about any potential effects on retinal health in the longer term,” she stated.
Take home?
While Downie concluded that the review evidence is inconclusive and uncertain in determining support for wearing blue light lenses, she concluded that “Our findings do not support the prescription of blue-light filtering lenses to the general population.”
What’s next?
Downie recommended high-quality, larger clinical research studies with a longer follow-up time among more diverse populations are needed to determine a more clear picture of the potential benefits blue-light filtering lenses may offer.