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J. Hong, H. J. Hofer; Is Optimal Modal Control a Worthwhile Strategy for Adaptive Optics for the Human Eye?. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2776.
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© ARVO (1962-2015); The Authors (2016-present)
It has recently been suggested that an optimized modal control scheme can improve the quality of astronomical images acquired with adaptive optics1. We sought to determine if there are similar potential gains to be had with optimal modal control for adaptive correction of the aberrations of the human eye.
We calculated the optimal gains for traditional adaptive control and for an optimal modal scheme whereby a different gain may be employed for each spatial mode using previously published data on ocular aberration dynamics 2. We then estimated the impact of optimal modal control on retinal image quality by using previously measured time-resolved aberration sequences for several individual subjects3 as the input to a theoretical simulation of the action of a high-resolution adaptive optics system modeled with the pre-calculated modal or fixed gains and including noise. Resultant image quality was then estimated by computing the time-averaged Strehl ratio and MTF of the theoretical residual aberration. We then repeated this simulation after optimizing the fixed and modal gains individually for each subject in order to achieve maximum Strehl ratio.
1) In simulations the optimal modal control scheme improved Strehl ratio 5-50% depending on noise. 2) Large differences were predicted across subjects both in the benefit of optimal modal control and in the specific gain parameters required for maximum benefit. 3) Allowing optimal modal and fixed gains to vary for each individual significantly increased the Strehl ratio, compared with using the gains obtained from averaged power spectral data.
Optimal modal control for human eye adaptive optics offers modest potential benefit when working with large pupil sizes or when constrained to high noise or low light situations. As expected, the magnitude of the benefit is predicted to be highly variable across subjects due to individual variations in aberration structure. To achieve the maximum benefit it may be necessary to dynamically change system gains according to each individual’s aberration structure.1. L.A. Poyneer and J.P. Veran, "Optimal modal Fourier-transform wavefront control," J. Opt. Soc. Am. A. 22, 1515-1526 (2005).2. H. Hofer, P. Artal, B, Singer, J.L. Aragon, D.R. Williams, "Dynamics of the eye’s wave aberration," J. Opt. Soc. Am. A. 18, 497-506 (2001).3. G. Yoon, H. Hofer, L. Chen, B. Singer, J. Porter, Y. Yamauchi, N. Doble, D. R. Williams, "Dynamic correction of the eye's aberration with the Rochester 2nd generation adaptive optics system". Invest Ophthalmol Vis Sci. 42, Abstract nr 545 (2001).
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