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G. Yoon, R. Sabesan, M. Gilbert; Effects of Higher Order Aberrations on Night Myopia Using Adaptive Optics. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2837.
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© ARVO (1962-2015); The Authors (2016-present)
To assess whether or not higher order aberrations, especially spherical aberration are partially responsible for causing night myopia in normal young eyes.
Five normal young subjects (5 eyes) participated in the study. Subject’s refractive errors were measured for 3 mm and 6 mm pupils at photopic (100 cd/m2) and mesopic (0.1 cd/m2) luminance levels, respectively. Subject’s pupil was dilated with Phenylephrine Hydrochloride (2.5%) and the pupil sizes were controlled with an artificial aperture placed in pupil conjugate. Myopic shifts of the refractive error under the mesopic condition were measured with and without spherical aberration corrected. An adaptive optics system (AO) was used to measure and to correct spherical aberration. The polychromatic modulation transfer functions (MTF) based on photopic and mesopic spectral luminous efficiencies were also calculated for each of the experimental conditions.
RMS values of spherical aberration under photopic and mesopic conditions for a 6 mm pupil were 0.17±0.15 µm and 0.15±0.16 µm on average, respectively. Other higher order aberrations did not significantly differ between the two conditions. With AO correction, spherical aberration was reduced to 0.016±0.017 µm. Average magnitudes of night myopic shift with and without spherical aberration corrected were -0.95±0.57 D and -0.80±0.49 D, respectively. This difference was statistically insignificant (p = 0.11). The MTF calculations showed that chromatic aberration may contribute approximately -0.2D of night myopia.
In young normal eyes, monochromatic spherical aberration does not have a significant impact on night myopia. Night myopia does not cause changes in higher order aberrations. Contribution of the difference in spectral sensitivity of cones and rods to night myopia may be relatively small, but significant. The predominant cause of night myopia seems to be an involuntary accommodative state of the crystalline lens under dim light condition.
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