A new report published in the journal Optometry and Vision Science may have some advocates of blue-blocking lenses seeing red. That’s because, in a study of 33 patients with digital eyestrain, blue-blocking lenses were deemed approximately as effective at reducing symptoms as only using a equiluminant neutral-density filter.

Blue light—found in the wavelengths between 400nm and 500nm—can have several deleterious effects, including eye fatigue, dry eye symptoms, alteration of circadian rhythms and damage to the photoreceptors of the retina. These and other related issues may be on the rise as people spend more and more time in front of blue-light emitting devices such as computers and smartphones. These conditions are collectively referred to as “digital eyestrain.”

The New York based researchers asked study participants to undertake a 30-minute reading exercise on a tablet computer with either a blue-blocking lens (which block 99% of blue light) or a neutral-density filter that produces equal screen luminance and blocks more than 50% of blue light. Preceding these sessions, subjects viewed a distant visual acuity chart at five meters for five minutes straight. While viewing the far target, five readings of the refractive state of the left eye were recorded using an open-field, infrared, Grand Seiko WAM-5500 optometer. These values served as the baseline reading for the within-task measurements of the accommodative response, the report explains. At the end of each session, subjects were asked to fill out a questionnaire regarding any relevant symptoms.

The answers show that, whether the patients blocked approximately 50% or 99% of blue light, the effect on digital eyestrain was about the same. These results contribute to the prevailing thinking that little evidence supports the use of blue-blocking lenses to improve visual performance or alleviate eye fatigue. The researchers suggest that, “further research into the efficacy of blue-blocking filters is required before they can be advocated as a treatment for digital eyestrain.”