December 15, 2020
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Smartphone screens are ‘least disturbing’ to ocular surface vs other devices

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Smartphone screens produced the fewest visual disturbances to the ocular surface, while researchers observed highest disturbances after computer use, according to findings published in Optometry and Vision Science.

“[I]t is expected that the differences in the nature of the displays and the ways in which they are set and used may contribute to differences in the eye-related problems they cause,” Cristian Talens-Estarelles, MSc, and colleagues wrote. “The purpose of the current study was to analyze the differences in dry eye signs and symptoms and visual fatigue of young subjects after carrying out a reading task on four different digital displays and after a baseline measurement, under two different measurement conditions: with and without initial instillation of artificial tears.”

Talens-Estarelles and colleagues enrolled 31 healthy volunteers (mean age, 21.26 years) in a prospective clinical study. They assessed participant ocular surface, tear film and visual fatigue parameters at baseline and after 15 minutes of laptop, tablet, e-reader and smartphone use for each participant with and without artificial tears.

Participants reported owning two or more digital devices, with 60% owning three or more, and using digital displays for an average of 9.3 hours per day. Outcome measures included Ocular Surface Disease Index (OSDI) score, Computer Vision Syndrome Questionnaire (CVS-Q), tear meniscus height, Schirmer I test, noninvasive keratograph break-up time, osmolarity and bulbar redness.

Researchers wrote that the “[b]est results were obtained with the smartphone and the e-reader,” while “the computer produced the highest disturbance on the ocular surface and tear film.” OSDI and CVS-Q scores were lower after e-reader (OSDI: 4.5; 95% CI, 1.3-7.6; CVS-Q: 1.7; 95% CI, 0.9-2.4) and smartphone use (OSDI: 5.2; 95% CI, 1.8-8.5; CVS-Q: 2.7; 95% CI, 1.9-3.6) compared with computer use (OSDI: 11.3; 95% CI, 6.9-15.6; CVS-Q: 5; 95% CI, 3.8-6.2).

Tear meniscus height and Schirmer I tests were similar after e-reader (tear meniscus: 0.31 mm; 95% CI, 0.27-0.35; Schirmer I: 36.94 mm; 95% CI, 18.81-55.05) and smartphone use (tear meniscus: 0.3 mm; 95% CI, 0.27-0.34; Schirmer I: 39.6 mm; 95% CI, 20.6-58.59), compared with a 0.26 mm tear meniscus (95% CI, 0.22-0.3) and 27.92 mm (95% CI, 15.02-40.81) after computer use. Noninvasive keratograph break-up time was also similar after participants used e-readers (12.6 seconds; 95% CI, 10.12-15.08) and smartphones (12.62 seconds; 95% CI, 10.21-15.03), compared with 11.5 seconds (95% CI, 9.29-13.7) after using a laptop.

Osmolarity and bulbar redness were greatest after computer use (osmolarity: 293.74 mOsm/L; 95% CI, 291.37–296.12; bulbar redness: 0.75; 95% CI, 0.64–0.85), followed by e-reader use (osmolarity: 291.55 mOsm/L; 95% CI, 289.2–293.9; bulbar redness: 0.7; 95% CI, 0.61–0.78) and then smartphone use (osmolarity: 288.58 mOsm/L; 95% CI, 286.74–290.42; bulbar redness: 0.62; 95% CI, 0.53–0.71).

Researchers wrote that the artificial tears did not have a significant effect.

“Best results were obtained with the smartphone and the e-reader, probably attributed to a lower gaze angle accompanying smartphone visualization and to the enhanced optical properties of the e-reader,” researchers wrote, also noting that, “the e-reader reflects rather than emits light from behind the screen, similarly to how a printed paper behaves.

“Taking into account the clinical tests for dry eye diagnosis, the smartphone may be considered as the least disturbing display.”