Subjects. Thirty-four young adults 19 males & 15 felames, age 18-33, mean age = 24.8) participated in this study. They all have 20/20 or better vision for each eye, no eye strain history, and at least 6 months of handheld use experiences. A written consent for recording their postures was obtained prior to the test of the study. Apparatus. Three handheld devices were chosen to be tested: Apple iPod: 2.5” LED backlight color display, 320x240 pixels, 163 ppi, weight 4.8 oz, One thumb- scroll wheel for single-hand operation. Sony PSP: 4.3” TFT LCD widescreen, 480x272 pixels, 10 oz, Two thumb-operating button area. HP iPAQ HW6945 smartphone: 3” TFT LCD touch screen, with LED backlight & stylus, weight 6.33 oz. Tasks. The subjects was asked to perform 5 typical handheld-use tasks for 10 minutes each on 3 selective handheld devices: Watching an animated movie on a portable media player (Apple iPod) Playing jigsaws on a game station (Sony PSP 2) Keying text messages, searching a film database, and reading word documents on a smartphone (HP iPAQ hw6945). For comparison, subjects were aslo asked to read text on hardcopy at font size 6, 7, 8, 10, and 12 point to examine the effect of text resolution on viewing distance. Target measurements Viewing distance was recorded with a videocamera and measured offline by sampling one frame per min. Surface-electromyography (EMG) response of the right orbicularis ocular muscle (0.5~1.0 cm under the lower eyelid) was measured as an objective index of visual discomfort. Subject’s subjective rating of visual and body discomfort was obtained through an analog questionnaire (Analog Sensation Questionnaire) at the end of each task. The derived measures were compared to that in reading novels with text at regular (12- or 10-point) or smaller (8-, 7-, or 6-point) font sizes. Viewing Distance & Visual Discomfort Associated With the Use of Handheld Computer Devices Yu-Chi Tai, James Sheedy, John Hayes, James Kundart, Hannu Laukkanen College of Optometry Pacific University, Forest Grove, Oregon CONCLUSION Viewing distance at hardcopy reading was a compromised result of text resolution (the viewing angle of the text), individual’s visual acuity and the resulted accommodative stress. Reading 12-point font results in viewing distance of 49 cm, closed to the theoretical accommodative demand of 2 Diopter (50 cm). As font size decreased (10-, 8-, 7-, to 6- point), viewing distance became closer (47, 45, 44, 40 cm, respectively), which increased the accommodative demand. which eventually posted a limit to the visual angle for how much it could be increased. In contrast, viewing distance at handheld conditions was significantly closer (30.3 ~ 42.7 cm) than reading hardcopy at similar or smaller sizes (F(1, 75.2)= , p<.0001). Further analysis suggests that the nature of the task (Table 1) is responsible for the close distance. When the task was more cognitively (t(132) = , p<.0001) or visually (t(132) = 6.991, p<.0001) demanding and required more active motor responses (t(132) = 8.514, p<.0001), viewing distance was shorter. No difference was found for EMG power, though blink frequency was much lower for handheld use than hardcopy reading. Subjects reported higher level of backache/neck pain and eyestrain sensation, especially when playing games and searching database. Handheld computer devices (HCDs) have become widely used in recent years by the general public, from game consoles for preschoolers to handheldmed for medical profession. In this study we measured the viewing distance while using HCDs and evaluated its effects on ocular and musculoskeletal symptoms of discomfort. With brief use of handhelds, significant difference was observed at viewing distance, blink frequency, and subjective discomfort sensation, which seem to result from the nature of the task. Periodic resting is suggested to relieve discomfort symptoms. This study was supported by a grant from The Advanced Reading Group of Microsoft Corporation to James E. Sheedy. Principal Investigator: Yu-Chi Tai ( ; ABSTRACT METHOD RESULTS ACKNOWLEDGEMENTS CONTACT INFORMATION