E-sports or electronic sports have been attracting a lot of attentions especially younger audience with the promise of wealth just through playing video games. Staring into monitor screen regardless of devices for an extended amount of time will lead to Digital Eye Strain (DES) in general, more particularly visual fatigue. The study is to explore the effect of extended exposure of blue light wave while playing video games to gamers, focusing on DOTA players. This study will investigate visual fatigue with and without blue light monitor filter. From a total of 20 participants who were recruited, 10 participants performed the experiment with blue light monitor filter and the remaining without blue light monitor filter. Visual fatigue was measured by the perceived frequency of light observed by each participant using critical flicker frequency (CFF) before and after the experiment. Participants were also required to perform subjective evaluation (SE) by answering questionnaire on visual fatigue symptoms that they experienced after the experiment. SE was used to establish correlation between the reading obtained from CFF to determine visual fatigue. The result shown that With_Filter and Without_Filter scored a positive and negative average difference in CFF score respectively. Teary eye was discovered to be the most common symptom in With_Filter and Without_Filter group although Without_Filter group experienced more symptoms than With_Filter group such as red eyes, twitching eyelids, blurred near and distant vision, and pain in and around eyes.