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Rachel Williams, Suyash Bakshi, Edwin Ostrin, Lisa A Ostrin; Objective, continuous measurement of near work, light exposure and activity. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4143.
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© ARVO (1962-2015); The Authors (2016-present)
Low light exposure and high amounts of near work are known risk factors for myopia. Objective measurements of light exposure are possible; however, quantification of near work only assessed subjectively, which is subject to poor recall and biases. The goal of this study was to objectively quantify near work with a custom built device, the RangeLife, and correlate findings with light exposure and activity.
The RangeLife device consists of an infrared time of flight sensor programmed to log distance at 1 Hz, mounted on the right temple of a spectacle frame and directed 4° nasally. Adult subjects (n = 20) wore the device for waking hours on a weekday and weekend day, and maintained a log of activities. Additionally, subjects answered a visual activity questionnaire and wore an accelerometer and light sensor (Actiwatch Spectrum). RangeLife data were binned into 0.10 m intervals and compared to the log entries. Each interval from 0.1 to 1 m was assigned a category from very near to far intermediate working distance. Distances greater than 1 m were considered distance for the purposes of this study. Subjective (questionnaire) and objective (RangeLife) diopter hours were calculated.
An average (±SD) of 761 ± 115 minutes of data were collected each day. On weekdays, subjects spent 340 ± 154 minutes engaged in distance viewing and 426±108 minutes engaged in near to intermediate viewing, with the highest frequency working distances from 0.3 to 0.7 m. On weekends, subjects spent 366±205 minutes in distance viewing and 284±95 minutes in near viewing. Subjective diopter hours was 26.8±10.6 on weekdays and 19.7±18.6 on weekends. Objective diopter hours was 15.9±4.3 on weekdays and 10.9±4.7 on weekends. Actiwatch data showed that the majority of time spent doing near work was in illumination levels of 50-500 lux, and at activity levels of 0-250 counts per minute (ie “light” physical activity).
The RangeLife provided continuous and objective measurements of working distances. On weekdays, adult subjects tended to spend over half of the recorded time engaged in near viewing, with increased subjective and objective diopter hours compared to weekend days. In future studies, the RangeLife device will be utilized to assess near work behaviors between myopic and emmetropic individuals to help elucidate the role of near work in refractive error development.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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