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R. Sabesan, G. Yoon; Correcting Highly Aberrated Eyes Using Large-Stroke Adaptive Optics. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2777.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the optical performance of a large-stroke deformable mirror in correcting large amounts of aberrations in highly aberrated eyes
A large-stroke deformable mirror (Imagine Eyes: MIRAO-52D) and a Shack-Hartmann wavefront sensor were used in an adaptive optics system. Individual Zernike modes up to the 5th order with varying amplitudes were produced using the mirror. Closed-loop correction of the static aberrations of a phase plate, designed for an advanced keratoconic eye, was performed for a 6mm pupil. The same adaptive optics was also used to correct the aberrations in 3 keratoconic (1 advanced and 2 moderate) and 3 normal eyes for a 6mm pupil. Defocus and astigmatism were partially compensated using a Badal system and a phoropter in the highly aberrated eyes, prior to closed-loop correction, to conserve the dynamic range of the mirror. The residual aberrations were averaged over 5 seconds after correction to determine the overall corrective performance.
The influence functions of the actuators as a function of the applied voltage showed 99.99% linearity. The maximum strokes measured for central and peripheral actuators were 38.43 µm and 27.36 µm in wavefront, respectively. This large dynamic range of the mirror allowed individual 2nd order Zernike modes up to 7 µm RMS, 3rd order modes up to 5 µm RMS, 4th order modes up to 2 µm RMS and 5th order modes up to 0.5µm RMS to be accurately produced with negligibly small error. In closed-loop correction, the total RMS of the phase plate over a 6mm pupil was reduced from 3.54 µm to 0.038 µm in 10-15 iterations, corresponding to 1-1.5 seconds. The 3 normal eyes had an average total RMS (higher order RMS) of 1.78 ± 0.86 µm (0.32 ± 0.14 µm) and 0.089 ± 0.01 µm (0.05 ± 0.01 µm), before and after closed-loop correction respectively. For the 3 keratoconic eyes, that have higher amplitudes of higher order aberrations, adaptive optics reduced an average total RMS (higher order RMS) of 3.54 ± 1.79 µm (2.71 ± 1.42 µm) to 0.23 ± 0.11 µm (0.17 ± 0.13 µm) in closed loop correction.
Aberrations in both normal and highly aberrated eyes were successfully corrected using the large-stroke deformable mirror. This mirror can be a powerful tool to assess the limit of visual performance achievable after correcting the aberrations, especially in eyes with abnormal corneal profiles.
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