Blue-light filtering lenses, commonly known as blue-blocking lenses, have no significant effect in lessening eye strain caused by extended computer use, according to a study published in the American Journal of Ophthalmology.
Researchers at the Department of Optometry and Vision Sciences at The University of Melbourne conducted a double-masked, randomized controlled trial on 120 participants to learn if blue-blocking lenses might help reduce the eye strain people felt after extended periods of screen time.
Participants were screened over the phone with a questionnaire regarding computer vision syndrome (CVS). They were limited to individuals between the ages of 18 years and 40 years and who used computers regularly without corrective spectacles, and possessed unaided or contact lens-corrected binocular near vision of print size N8 or larger at 40 cm. Possible participants were excluded if they had a history of self-reported neurological disease or migraine, or nystagmus, or had a professional background in eye care.
The participants were randomly sorted using a 2-tier process. In the first tier, each participant was assigned to a group where one of the researchers advocated for or against wearing blue-blocking lenses. This allowed the researchers to better simulate clinical practice — where prescribed therapies are almost always presented favorably — as opposed to the equivocal tone often used in trials. Next, participants were randomly assigned either blue-blocking lenses or clear placebos. However, they were all led to believe that they had been given blue-light filtering lenses — again in keeping with clinical practice, where patients never expect to receive placebos.
After pre-task measurements, the participants were asked to complete standardized computer tasks involving spreadsheet data entry and data checking for 2 hours. The same measurements were taken immediately afterwards, for comparison.
Researchers found that for critical flicker-fusion frequency,no significant difference exists between blue-blocking and control spectacle lenses (between-group point estimate difference: -1.33, 95% CI, -3.22 to 0.55, P =.164) and no effect depending on advocacy type (between-group point estimate difference: -0.98, 95% CI, -2.86 to 0.90, P =.304). Similarly, for eye strain symptom score, there was no effect depending on the lens type (between-group point estimate difference: -18.3, 95% CI, -60.8 to 24.1, P =.394) or advocacy type (between-group point estimate difference: -17.6, 95% CI, -59.9 to 24.6, P =.410).
With CVS affecting an estimated 60 million people worldwide, the blue light emitted by computer screens has emerged as a hypothetical cause of eye strain and blue-blocking lenses as a possible solution.
However, the researchers disagree with this. “The results of our study, combined with the low blue light emission from electronic devices and the lack of a plausible causative mechanism, mean that it is extremely unlikely that blue light is a contributory factor to eye strain associated with computer use,” the report says.
The study was limited in that the protocol was not published or registered and the study itself involved participants recruited from an optometry college, who may have had professional knowledge about blue-blocking lenses and could potentially have recognized them by sight.
Singh S, Downie L, Anderson A, Do blue-blocking lenses reduce eye strain from extended screen time? a double-masked, randomized controlled trial. Am J Ophthalmol. Published online February 9, 2021.doi:10.1016/j.ajo.2021.02.010.