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Renjing Tan, Jinhua Bao, Bjorn Drobe, Hao Chen; Effects of illuminance and contrast on reading distance in young Chinese myopic adults. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2945.
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© ARVO (1962-2015); The Authors (2016-present)
To compare reading distance for different illuminances and different contrasts of printed materials in Chinese myopic young adults.
We recruited 24 Chinese myopic young adults (aged 20 - 30 years) with a spherical equivalent between -1.50 D to -8.00 D in both eyes with best visual acuity no less than 1.0 wearing spectacles. Task consisted in reading one A4 page while the subjects’ reading distance was recorded at 15 Hz using an electromagnetic motion tracking system (Fastrack, Polhemus, USA). Each subject performed 8 consecutive reading tasks for 4 different illuminance (3 lx / 30 lx / 300 lx / 600 lx) and 2 contrast (Grey: 44.6%, Black: 90.3%) conditions in random order. For analysis, reading distance was defined as the distance from the base of the nose of the subject to the centre of each line, averaged over the whole page.
Reading distance significantly increased with illuminance (F = 28.20, P < 0.001), as well as with contrast (F = 26.04, P < 0.001) with a significant interaction between illuminance and contrast (P = 0.002). Average reading distances were 24.7 ± 4.1 cm (Grey, 3 lx; G3), 29.7 ± 5.3 cm (Grey, 30 lx; G30), 31.9 ± 6.8 cm (Grey, 300 lx; G300), 33.2 ± 5.6 cm (Grey, 600 lx; G600), 28.5 ± 4.2 cm (Black, 3 lx; B3), 31.3 ± 4.3 cm (Black, 30 lx; B30), 33.1 ± 6.1 cm (Black, 300 lx; B300), and 32.4 ± 5.8 cm (Black, 600 lx; B600). Significant differences were found between G3 and G30 (P < 0.001), G30 and G300 (P = 0.004), G300 and G600 (P = 0.049), B3 and B30 (P < 0.001), G3 and B3 (P < 0.001), G30 and B30 (P = 0.019). The order in which each subject performed the tasks had no effect on results (P > 0.05).
Illuminance and contrast appear to be key factors for adjusting working distance at near in myopic adults. 300 lx illuminance with high contrast on printed materials is an optimum suggestion to obtain ideal near reading distance.
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