Changes in Tear Lipid Layer Thickness After Short Exposure to Light Emitting Diode Displays

Video display terminals (VDTs) are ubiquitous, and engagement in digital screens has grown substantially across all age groups worldwide. During the coronavirus disease 2019 (COVID-19) pandemic, lockdowns and increasing demand for digital learning and working have led to more frequent and sustained VDT use. Prolonged exposure to VDTs is associated with the development of various health problems, including psychosocial issues, venous thromboembolism, fatigue, and visual complaints.

Computer vision syndrome (CVS) is one of the most frequently encountered problems among VDT users. CVS comprises several visual and musculoskeletal symptoms resulting from VDT use, such as eye strain, dryness and burning sensation of the eye, blurred vision, and neck and shoulder pain. A major alteration is the development of dry eye disease (DED), occurring in 60 % of those with CVS. Dry eye symptoms, corneal erosions, short tear-film breakup time (BUT), low tear meniscus height, and meibomian gland dysfunction (MGD) are all DED presentations encountered by VDT users. The continuous use of VDTs is an established risk factor for CVS and DED. However, it is unclear whether transient exposure to VDTs leads to ocular surface changes, especially regarding lipid layer thickness (LLT).

This study investigated if the short-term use of light-emitting diode (LED) displays (one type of VDT) changed the ocular parameters, including best-corrected visual acuity (BCVA), intraocular ocular pressure (IOP), the CVS-Questionnaire (CVS-Q) score, the blink rate, the partial blink ratio, and LLT. To our knowledge, this is the first study to focus on the immediate effects of LEDs on the eye.

This prospective clinical study was conducted in the Ophthalmology Department of the National Cheng Kung University Hospital (NCKUH), Tainan, Taiwan. The study was approved by the Institutional Review Board of NCKUH and followed the tenets of the Declaration of Helsinki. Written informed consent was obtained from all the participants.

The inclusion criteria were generally healthy individuals aged between 20 and 65 years who were willing to participate in the study. The exclusion criteria were ages below 20 or over 65 years, a BCVA score of <0.1 on the Landolt C chart in either eye, a BCVA difference of >0.2 between the eyes, and a history of ocular diseases or previous ocular surgery.

Participants were instructed to fill out a basic information form, including their name, sex, age, and contact information. They were also informed to avoid wearing contact lenses for two days before the test. The experiment was conducted on August 22, 2020. For the baseline test, the participants were asked to complete the CVS-Q to assess their CVS. Next was a series of ocular examinations, including BCVA, IOP, LLT, an optical coherence tomography (OCT) scan of the macula, and fundus autofluorescence (FAF) imaging. The LLT and blink rates were measured using the LipiView II Ocular Surface Interferometer following the standard protocol (TearScience, Morrisville, NC, USA). After the examination, the participants watched a short movie on an LED screen (InnoLux, Taiwan) for 15 minutes in a bright room. The viewing distance was approximately 1.5 meters. After the movie ended, the participants were instructed to complete the CVS-Q and undergo the BCVA, IOP, and LLT tests again. The baseline BCVA, IOP, OCT, and FAF images of each participant were reviewed by three NCKUH ophthalmologists to screen for clinically significant ocular pathology.

Statistical analyses were performed using R software version 4.1.0 (R Core Team, Vienna, Austria) and SAS Enterprise Guide (version 9.4; SAS Institute Inc., Cary, NC, USA). Paired t-tests were used to compare the BCVA, IOP, CVS-Q score, LLT, blink rate, and the partial blink ratio before and after watching the LED display. Statistical significance was set at P <0.05.

Inclusion criteria

• generally healthy individuals aged between 20 and 65 years who were willing to participate in the study

Exclusion criteria

• ages below 20 or over 65 years
• a BCVA score of <0.1 on the Landolt C chart in either eye
• a BCVA difference of >0.2 between the eyes
• a history of ocular diseases or previous ocular surgery