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According to the results of a recent study published in the Journal of Optometry, binocular and accommodative anomalies do not appear to be major contributors to digital eyestrain, previously known as computer vision syndrome, and patients with a esophoric fixation disparity on the near Mallett unit may benefit from near low-powered addition lenses.
The visual and ocular symptoms experienced when using digital devices may be external, such as dry eye, or internal, relating to refractive, accommodative, or binocular vision anomalies.
The investigators aimed to determine if any internal, binocular or accommodative, factors could explain why participants with digital eyestrain perform better on the Wilkins Rate of Reading Test (WRRT) with +0.75DS near addition lenses and subjectively prefer them, as demonstrated in previous studies.
Potential participants were recruited from the London area with local advertisements and via word of mouth. Those with digital eyestrain were identified using the Computer Vision Syndrome Questionnaire [CVS-Q], a validated tool to quantify the prevalence and severity of visual and ocular discomfort associated with using a digital display. Those included in the study had a CVS-Q score (≥6) suggestive of digital eyestrain, spent at least 6 hours per week on a digital device, and exhibited no recent onset incomitancy or constant strabismus.
The 107 participants, who had a mean age of 31 years (range, 20-40 years), each underwent a comprehensive eye examination. The median CVS-Q score was 16 (range, 6-36). The investigators then assessed the effects of low-powered addition lenses (+0.50D, +0.75D, and +1.25D; and plano controls) by double-masked testing with the WRRT and subjective preference.
Most (80%) participants subjectively preferred 1 of the 3 convex lenses, with +0.75D chosen most frequently. Most (88%) participants also read faster in the WRRT with addition lenses, and reading rate was significantly improved with +0.50D (P <.001) and +0.75D (P <.0001), but not +1.25D, lenses relative to the control lenses.
Using a variety of diagnostic criteria, the investigators did not identify any strong associations between WRRT results or CVS-Q scores and any binocular or accommodation functions. However, they did find that a disproportionate number of participants with an esophoric fixation disparity on the near Mallett unit (5/7) benefited from addition lenses.
The primary limitation of the study was the lack of a control group without digital eyestrain. Another potential limitation was that the %WRRT was recorded as zero rather than as a negative value for participants who read fastest with the control lenses, which would mean any slowing effect of addition lenses for these participants was discarded.
“[A]lthough binocular and accommodative anomalies are prevalent in [digital eyestrain], they cannot explain the benefit of low plus addition lenses. It is possible that the accommodative relief offered by these lenses is a simple explanation of their benefit,” according to the researchers. “Finally, dry eye as well as binocular and accommodative anomalies, is common in people with the multifactorial condition of [digital eyestrain]. A comprehensive eye examination is warranted to detect these problems.”
Disclosure: This research was supported by Hoya Holdings NV, the Netherlands. Please see the original reference for a full list of disclosures.
Reference
Yammouni R, Evans BJW. Is reading rate in digital eyestrain influenced by binocular and accommodative anomalies? J Optom. 2021;14(3):229-239. doi:10.1016/j.optom.2020.08.006
