Effect of Smart Phone Reflective Light Film on Dry Eyes and Asthenopia

Overview

This study aimed to evaluate the effect of anti-reflection (AR) and circularly polarized (CP) film on video display terminal (VDT) induced dry eye and asthenopia after limited time and close distance of visual tasks under light and dark environment, searching for new strategy for eye-protective electronic screen. The study was randomized, double-blind and controlled. Subjects were enrolled following the criteria: diopter of both eyes not exceeding -6.0D and anisometropia not exceeding 2.0D. and randomly divided into control, AR, AR+CP group in light or dark environment. Character searching, gaming and video tasks utilizing specific smartphones for totally 45 minutes were performed. Researchers measured the indexes of dry eye and asthenopia before and after tasks to evaluate impacts induced by VDT.

The inclusion criteria required volunteers to have myopia diopter not exceeding -6.00D, hyperopia not exceeding +2.0D, astigmatism not exceeding -2.00D, anisometropia between both eyes not exceeding 2.00D. The key exclusion criteria were as follows: (1)strabismus and amblyopia; (2)used eye drops within 1 week; (3)had undergone eye surgery within 6 months; (4)worn contact lenses within the last 2 weeks; (5)had serious eye discomfort in the last 7 days; (6)Breastfeeding or pregnant women and patients with severe systemic diseases, psychosis or dementia. Subjects who met the criteria were divided into five groups. 3 groups using non-processing smartphone screen, anti-reflection screen and anti-reflection plus circular polarization screen read in light environment and 2 groups using non-processing screen and anti-reflection plus circular polarization screen read in dark environment. Subjects did not know the characteristics of the smartphones they use. Subjects met the requirements were randomly grouped. The subjects did not use video terminals such as mobile phones within 30 minutes before the study began. During the whole experiment, light-group subjects were in a room with normal indoor ceiling light, correlated colour temperature 3904K, desktop illuminance 388.7lux, screen brightness about 150nit, while dark-group in environment illuminance 0.02lux, screen brightness about 6nit. Light source stability (working surface illuminance fluctuation) greater than 99% during the whole experiment, desktop range uniformity greater than 80%. Desktop matte treatment without special reflection, indoor air conditioning control temperature: 22-25 degrees Celsius, humidity: 50-70%RH. Users placed it on a fixed mobile phone stand (the angle and height of the mobile phone stand can be adjusted to make sure all subjects could see reflection of the lamp on ceiling behind them from the smartphone black screen state). All subjects' eyes are 40cm away from the mobile phone screen, and they sit on a chair of appropriate height and fixed position. Two groups of subjects would complete the following three tasks in definite order: 1) Character searching task (5 minutes) : Subject read a meaningless text on the screen, found all the target characters in it, and told researchers about the statistics; 2) Game task: Subject played one of several pre-installed games requiring high concentration and eye tracking for 20 minutes; 3) Video task: Subject watched the video Animal World with the mobile phone for 20 minutes. During the study period, subjects should not do any behavior unrelated to watching the screen for a long time (more than 1 minute). We evaluated the subjects' basic ocular data: best corrected visual acuity(BCVA), spherical equivalent(SE), subjective questionnaires including Ocular Surface Disease Index(OSDI), Computer Vision Syndrome Scale 17 (CVSS17); dry eye comprehensive analysis before and after the experiment respectively: tear meniscus height(TMH), noninvasive tear break-up time(NIBUT), fluorescein tear break-up time(FBUT), corneal fluorescein staining(CFS), Schirmer I tear secretion test; asthenopia related examination: High-frequency component(HFC) and blink frequency.