Objectives: Computer usage has rapidly grown. This is because it helps to resolve problems, i.e., encountered in daily life by individuals. Various monitor screens that have been developed affect the user’s eyes. Screen size is one of the relevant impacts. Thus, this study compared the immediate effects of two computer screen sizes on visual fatigue in Video Display Terminal (VDT) users.
Methods: Twenty female VDT users participated in this study. Using a randomized block design for the study, the study participants randomly drew a ballot to determine the order of using an 18.5-inch and 23-inch computer screen size. The research participants were assessed by a visual fatigue score, critical flicker frequency, and dry eye score before and after using both computer screen sizes. They were tested in an ergonomic computer workstation for 2 hours. Besides, where they rested between each workstation for ≥30 minutes or until presetting no eye fatigue symptoms. The relevant data were compared between before and after using the computers and between the two different screen sizes. 
Results: The collected results suggested no significant difference in the visual fatigue score, critical flicker frequency, and dry eye score between using either computer screen sizes (P>0.05). However, there were significant differences in the visual fatigue score, critical flicker frequency, and dry eye score between before and after computer screen usage (P<0.05).
Discussion: Using both computer screen sizes resulted in increased visual fatigue, reduced critical flicker frequency, and increased dry eyes. The present study results can provide information in determining how to reduce risk factors and prevent visual fatigue from continuous computer use for a long time.