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M. Nowakowski, A. V. Goncharov, C. Dainty; Study of Ocular Aberrations as a Function of the Field Angle Within Young Population. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3323.
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© ARVO (1962-2015); The Authors (2016-present)
Adaptive Optics (AO) techniques have recently been used to improve retinal imaging over a small field (about 1 degree) that is closely related to the probing direction of a wavefront sensor. The purpose of this study was to measure ocular aberrations within central 10 deg visual field in order to establish how one could correct ocular aberrations over larger field than that achievable with current AO systems.
Fifteen young and healthy subjects were studied with an ocular aberrometer that incorporates the Shack Hartmann wavefront sensor, pupil-tracking system, Badal adjustment stage, fixation target and laser-diode probing beam. The aberrometer was used to measure ocular aberrations in the pupil plane at 0, 3 and 5 deg from the field center in the horizontal and vertical meridians on both sides. Two measurements were taken for each direction to minimize the optical effect of the tear film. The aberrometer demonstrated high repeatability of measurements for an artificial eye used for calibration.
Measurements of ocular aberrations as a function of the field angle for 6-mm pupil revealed several groups of eyes with different aberration functions. Furthermore, measurements clearly showed that the dominant aberration within the central field is astigmatism. Numerical analysis was performed as an attempt to identify those aberrations, which do not display large variation across the visual field. These are spherical aberration and coma, and therefore they can be easily corrected by a standard AO system.
The results show that for the young healthy population, the main contributor to the total amount of ocular aberrations is astigmatism, which varies across the central visual field. In light of this, improving AO-assisted retinal imaging systems requires additional optics to compensate for the residual astigmatism, especially in a wide-field operation mode.
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