Abstract:  Objective To compare the influence difference of digital eye strain between head mounted display (HMD) and desktop display (DP) when using for reading application. Design Two stage cross-over design study. Participants 42 college students aged 18-21 years old. Methods The subjects were randomly divided into two groups, 21 cases in each group. The first group used HMD first, and then used DP to read the same text for 40 minutes, with an interval of 30 minutes. The second group was in the reverse order. An open-field autorefractor was used to measure the refraction and accommodative lag before and after reading. Likert scale was used to record subjective visual fatigue scores before and after reading. Reading efficiency was defined as a product of reading accuracy and reading rate per minute. Main Outcome Measures Refraction, corrected visual acuity, accommodative lag, and visual fatigue scale score, reading efficiency. Results Using HMD, the diopter before and after reading was -0.045 (-0.56, 0.31) D and -0.025 (-0.45, 0.31) D, respectively (P=0.144), and the accommodative lag was (1.13±0.57) D and (1.16±0.62) D, respectively (P=0.612). The corrected visual acuity was 1.00 (0.8,1.2), 1.00 (0.8,1.2), respectively (P=0.978). There were no significant differences in refraction, accommodative lag and corrected visual acuity before and after reading with HMD. The subjective score of visual fatigue before and after reading was 0.50 (0, 3.25), 2.50 (1.00, 6.00), respectively (P=0.004). The mean value of visual fatigue score increased after reading, and the difference was statistically significant. Using DP, the diopter before and after reading was -0.070 (-0.50, 0.23) D and-0.020 (-0.50, 0.26) D, respectively (P=0.305), the accommodative lag was (1.09±0.58) D and (1.13±0.59) D, respectively (P=0.491), and the corrected visual acuity was 1.00 (0.8, 1.0), 1.00 (0.8, 1.0), respectively (P=1.000). There were no significant differences in refraction, accommodative lag and corrected visual acuity. The subjective score of visual fatigue before and after reading was 0 (0, 3.00), 3.00 (1.00, 6.25), respectively (P<0.001). The mean value of visual fatigue score increased after reading, and the difference was statistically significant. There were no significant differences in the variations of refraction variation (P=0.126), accommodative lag (P=0.962), corrected visual acuity (P=0.894) and visual fatigue score (P=0.160). There was a significant difference in reading efficiency between HMD and DP devices (P=0.009). The reading efficiency of HMD was lower than that of DP (20.11±6.09, 22.01±6.91, P=0.009). Conclusion Compared with DP, HMD did not cause more digital eye strain during 40 minutes text reading.  (Ophthalmol CHN, 2022, 31: 429-434)

Key words:  digital eye strain, head mounted display, accommodative lag