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Maciej M. Bartuzel, D. Robert Iskander; The impact of higher order wavefront aberrations dynamics on instantaneous retinal image quality. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5798. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate temporal characteristics of the retinal image quality using dynamic wavefront sensing and to test the hypothesis that instantaneous image quality can be either substantially higher or lower than that achieved from the temporal averaging of wavefront aberrations.
Retrospective data of ocular aberrations of 70 healthy subjects (aged from 18 to 35 y.o.) were analysed. The aberrations were measured in the far point using Complete Ophthalmic Analysis System (COASTM, Wavefront Sciences Inc.) with the sampling frequency of about 11.5 Hz in a series of 120 time samples. For each subject the measured wavefronts were rescaled to their minimum pupil diameter. Through focus curves of the visual Strehl ratio based on optical transfer function (VSOTF) were computed using the procedure of Yi et al. (J.Vis. 2010) and the VSOTF peak value, VSOTFmax(t), was identified for each time instant, t. The overall maximum and minimum values of VSOTFmax(t) were compared to the maximum VSOTF value, VSOTFmaxAv, obtained from the time-averaged wavefront.
The instantaneous maximum VSOTFmax was 35 ± 16 % (mean ± std) larger than VSOTFmaxAv. The instantaneous minimum VSOTFmax was 25 ± 11 % (mean ± std) smaller than VSOTFmaxAv. Temporal changes in VSOTFmax, corresponding to natural variations of higher order aberrations (HOA), did not contain outliers. The minimum and maximum instances are marked and plotted separately on the right side of the figure alongside with the through focus VSOTF calculated from averaged wavefront. Retinal image simulations of an E letter (logMAR = 0.1) corresponding to peak values in each curve are shown as an example of instantaneous image improvement and degradation.
The dynamics of wavefront aberrations provides us with a wealth of information that is often neglected through averaging, which in fact corresponds to treating the changes in HOA as noise. This study demonstrates that variations in HOA may not necessarily be noise but contain important information about the continuous visual process.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Figure. Left: An example of time dynamics of a VSOTF curve, instances where maximum and minimum VSOTF peak values occur are marked; Right: Through focus VSOTF curves for the average wavefront and time instances with maximum and minimum peak values. E letter retinal image simulations correspond to peak values of each curve. Pupil size for this subject was 3 mm.
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