Reading on specific types of smartphone screens can cause discomfort on the ocular surface, according to a study published in Clinical and Translational Science.

Researchers investigating the effect smartphone reading has on the ocular surface in dark and well-lit environments compared Organic Light-Emitting Diode (OLED) smartphone screens with electronic ink (eINK) versions. They say the results of their investigation suggest that OLED screens irritate the eye and may lead to  discomfort. 

The results were drawn from119 volunteers — all college students — asked to read on a smartphone screen for 2 hours. None of them had an ocular disease diagnosis, used topical eye drops or wore contact lenses within a month of the study nor did they have any history of eye surgery within 6 months of the study.

Participants were randomly divided into 4 groups based on the type of screen and the brightness of the light in their environments: light and OLED; light and eINK; dark and OLED; and dark and eINK. 


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Various ocular surface examinations, including noninvasive breakup time (NIBUT), noninvasive keratograph tear meniscus height (NIKTMH), ocular redness, fluorescein break-up time (FBUT), corneal fluorescein staining (CFS), meibomian gland (MG) assessment, Schirmer I Test and blinking frequency, were carried out on the volunteers both before and after their reading task. And symptoms were evaluated using the Ocular Surface Disease Index (OSDI) and Computer Vision Syndrome Questionnaire (CVS-Q).

Researchers found that the eye’s surface can be disturbed by continuous reading on an OLED screen. The NIBUT-First decreased significantly after reading on an OLED screen for 2 hours compared with the baseline in light and dark environments (P <.001, P <.001, respectively). Similarly, the NIBUT-Average (P <.001, P <.001) and FBUT (P <.001, P <.001) decreased after reading on an OLED screen in light and dark environments.

Meanwhile, reading on a eINK screen had less effect on eye redness, tear volume and the stability of the eye’s tear film.

Prior research shows that video display terminal-induced dry eye is often linked with unstable tear film. Here, researchers discovered that break-up time was significantly shortened after the reading task, especially for OLED screens; however the eINK screen did not cause a reduction in break-up time. 

The reason for this difference is primarily the different display technologies of the two screens. Unlike OLED screens, eINK screens display images by reflecting light from the natural world rather than emitting light, so they don’t produce blue light and avoid the increased eye redness that goes along with it. 

Researchers suggest optimizing smartphone screens may help protect the eye’s surface. Although OLED screens have some advantages, eINK screens appear to be friendlier to dry eye patients, according to the investigators. 

Reference 

Yuan K, Zhu H, Mou Y et al. Effects on the ocular surface from reading on different smartphone screens: A prospective randomized controlled study. Published online November 17, 2020. Clinical and Translational Science. doi: 10.1111/cts.12933.