The Comparison of the Effects of Invisible Flicker to Visible Flicker Light-Emitting Diodes (LED) Desk Lamp on Asthenopia

Introduction and Objective: Asthenopia defined as a sensation of visual fatigue, eye weakness, or eyestrain. It is frequently associated with situations where the accommodation and vergence process are more intense such as reading and writing. Asthenopia can be caused by flickering stimuli. Light-Emitting Diodes (LED) can produce flicker. The objective of this study is to compare the effect of invisible flicker LED desk lamp to visible flicker on asthenopia in college student at the library room.
Methods: This randomized, double blind, cross over clinical trial compared the asthenopia symptoms and to compared changes in the near point convergence (NPC), accommodative facility (AF) in subjects after doing 90 minutes visual demanding task using invisible flicker LED desk lamp and visible flicker LED desk lamp, with a 1 day break between crossover. Asthenopia assessment is done subjectively by questionnaire, and measured accommodation using flipper lenses and Royal Air Force (RAF) Ruler to assess the near point convergence objectively.
Results: In 44 subjects, there were no difference in the proportion of asthenopia and changes in the value of AF between 2 groups. There was a significant difference in NPC changes before and after intervention (invisible flicker: 0.67 (-2.17 - 5.08) cm; compare to that of visible flicker: 1.41 (-1.67 - 12) cm, p = 0.006). Burning eyes sensation was more common in invisible flicker LED users.
Conclusion: This study shows that the use of invisible flicker LED desk lamp minimize NPC changes after intervention for 90 minutes.