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Bjorn Drobe, Eu Jin Seow, Jinhua Bao, Yuwen Wang, Fan Lu; Near Vision Posture in Myopic Chinese Children. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2701.
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© ARVO (1962-2015); The Authors (2016-present)
To obtain the average working distance, eye and head declination of Chinese children during common near visual activities in order to create a specially designed progressive lens for children.
104, 2nd to 6th grade Chinese children, aged 6 to 14, underwent 3 near visual activities: reading a one-page text, copying 11 lines of Chinese characters and playing a hand-held video game. During these activities, relative head to document / video game positions were recorded at 10 Hz using a Polhemus Fastrack system. Average values of all recordings for each task were used for analysis. The spherical equivalent of the subjects ranged from -0.50 D to -6.50D.
Working distance was expressed as the distance between the base of the nose and the centre of each line of the document or the centre of the screen of the video game. Average working distances were 269 ± 61, 235 ± 55 and 217 ± 56 mm respectively for reading, writing and playing video game. Working distance significantly correlated with age for writing and playing video game (p<0.01), but not for reading (p=0.10). Head declinations were much higher when playing video game (64.8 ± 16 degrees) as compared to reading and writing (37.6 ± 12.8 and 47.1 ± 13 degrees). Eye declination was deducted from head declination and the point of interest was on the document and video game. Eye declinations were 19.6 ± 8.3, 17.5 ± 8.6 and 13.1 ± 6.8 degrees for reading, writing and playing video game respectively. Neither head nor eye declination was influenced by age (p>0.2).
Young myopic Chinese children adopt a very close working posture with mainly head declination during near visual activities, especially when playing video game. Progressive lenses for myopia control in children should therefore have shorter corridors (due to lower eye declination) and larger insets (due to shorter working distances) as compared to adults.
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