Galaxy tab s

Participants sat upright in a completely lightproof room, fixing on a red dot (diameter 1.67 mm) at eye level, which was presented on an active matrix LED screen (2,560 × 1,600 AMOLED, Samsung Galaxy Tab S) 55 cm away in front of them. We chose this type of tablet because its pixels are not backlit, eliminating any glow from the black screen background that might provide visual cues during SVV recording. In addition, subjects could only see the screen through a round opening, as the frame of the tablet mount was also covered by gaffer's tape to avoid reflections. Participants wore contact lenses or glasses as needed. SVV was measured in three head positions for each participant: upright (UP), 20° head tilt toward the right shoulder (right ear down or RED), and 20° head tilt toward the left shoulder (left ear down or LED). A molded bite-bar secured to a rotating tilt plate was used to passively position the head in the roll plane, and for measuring the angle of head tilt. Each participant was tested under all three head tilt positions in random succession, completing 100 SVV trials in each head position. We chose 20° head tilt because it is within the physiologic range of neck positions, and while comfortable to maintain during the recordings, it is large enough to induce SVV errors.

Data were collected using handheld Samsung (Seoul, South Korea) Galaxy Tabs with a 7-inch display running Android operating system; 50 tablets were used during the census, and 40 during the vaccination campaign. The software platform was built by a contracted partner (Majella Global Technologies, Portland, ME, USA) on Open Data Kit. External battery packs with dual USB charging ports provided a portable, backup power supply. Data records were first stored locally on devices in the field, and uploaded nightly via office Wi-Fi to a secure, web-hosted database. Online registries were subsequently downloaded nightly for analysis. All tablets and computers were password-protected and encrypted [24] , [25] .