[Influence of blue light from visual display terminals on human ocular surface]

Objective: To investigate the influence of blue light from visual display terminals (VDTs) on human ocular surface. Methods: Prospective intervention test Thirty volunteers were recruited to watch videos on the same VDT in a dark environment, about 40 cm from the screen. Volunteers were supposed to watch videos in the night shift mode that reduces the amount of blue light for 1 hour. At the same time of the second day, they watched the same videos on the VDT in the normal mode for 1 hour. Tear film break-up time (BUT), corneal fluorescein staining scores, lipid layer thickness (LLT), times of blinking in 19.1 seconds and the ratio of partial blinking in 19.1 seconds were measured before and after each watching. Meanwhile, volunteers were asked to complete a questionnaire about their subjective experience after watching. Results: BUT, corneal fluorescein staining scores and LLT showed no significant decreases in the volunteers after they watched videos on the VDT in the night shift mode [BUT before watching: (8.08±3.15)s, BUT after watching in the night shift mode: (5.31±2.49)s, t=-0.52, P>0.05], but there were significant decreases after they watched videos in the normal mode [BUT after watching in the normal mode: (3.35±1.95) s, t=2.40, P<0.05]. At the same time, there was a significant difference between night shift mode and normal mode[BUT after watching in the night shift mode (5.31±2.49)s, BUT after watching in the normal mode: (3.35±1.95)s, t=3.67, P<0.05). Times of blinking and the ratio of partial blinking in 19.1 seconds were increased modestly after watching in 2 different modes, but there was no significant difference(times of blinking after watching in the night shift mode were 5.55±3.27, times of blinking after watching in the normal mode were 5.93±3.59, t=-0.92, P>0.05). The questionnaire results showed that 70.0%(21) of the volunteers reported mild discomfort including eye dryness, itching, pain, foreign body sensation, redness and asthenopia, 46.7%(14) reported no difference between the 2 modes, 36.7%(11) preferred the night shift mode, 16.6%(5) felt better with the normal mode, and 80.0%(24) would like to try the night shift mode in their daily life. Conclusions: Use of VDTs for a short period of time can lower the stability of tear film. The night shift mode may cause less damage to the ocular surface than the normal mode. High-energy blue light from VDTs can be a risk factor in the ocular surface damage, but the damage is reversible. (Chin J Ophthalmol, 2018, 54: 426-431).