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Elena Grossmann, Philipp Hessler, Stephan Degle; Night Myopia and Dark Focus of Accommodation. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2153.
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© ARVO (1962-2015); The Authors (2016-present)
Shifts in accommodation at decreasing luminance levels are considered as main cause for night myopia. Previous studies with laser optometers quantified the dark focus of accommodation up to 3 D. In addition to the measurement of dark focus, the aim of this study was to investigate the influence of an imaginary target at finite distances on the state of accommodation at scotopic luminance.
Accommodation was measured by using an open-field autorefractor (WAM 5500, GRAND SEIKO). Full corrected right eyes of 39 subjects aged from 18 to 40 years were investigated in this randomized, cross-sectional study. Accommodation measurements in photopic luminance were taken for 6 m of empty field and for optotype fixation at 2 m, 1 m and 0.5 m. At scotopic luminance, dark focus of accommodation was examined directly after darkening and after 10 min of dark adaptation. After adaptation, subjects had to visualize imaginary targets in the four distances while accommodation was measured.
Compared to the photopic luminance level, accommodative shift in scotopic conditions (dark focus) was -0.22 ± 0.35 D (p < 0.001). There was no significant change in dark focus after dark adaptation (-0.26 ± 0.52 D). Accommodation on the targets was quantified at 2 m with 0.13 ± 0.27 D (photopic real target) and 0.05 ± 0.42 D (scotopic imaginary target), at 1 m with 0.40 ± 0.40 D (photopic real target) and 0.13 ± 0.51 D (scotopic imaginary target) and at 0.5 m with 1.01 ± 0.32 D (photopic real target) and 0.39 ± 0.56 D (scotopic imaginary target).
Changes in accommodation at decreasing luminance levels are minor measured by using an open-field autorefractor compared to other publications. However, dark adaptation has no impact on the state of accommodation. Even if the fixation was focused on a near imaginary target, accommodation was less than 0.5 D. In contrast to prior studies, dark focus of accommodation has less importance for night myopia than expected.
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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