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B. Sahin, F. Harms, B. Lamory, X. Levecq, R. Gillet, L. Vabre, C. Dainty; Improved Adaptive Optics Control System Using Pupil Tracking for High-Resolution Retinal Imaging. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2313.
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© ARVO (1962-2015); The Authors (2016-present)
Adaptive Optics (AO) which is used to correct the aberrations of the eye for high resolution retinal imaging needs to be fast enough to accommodate rapid eye movements. Here we evaluate a method that integrates pupil tracking into the AO system of the AO-Flood Illumination Fundus Camera (AO-FIFC) to enhance the temporal and spatial resolution of the AO system and improve the retinal image quality.
The AO loop of AO-FIFC includes HASO 32-eye wavefront (WF) sensor (10Hz), mirao 52-e deformable mirror (DM)(85 Hz), (both from Imagine Eyes, France) and a pupil tracking system (85 Hz). Between two WF gradient measurements;, the aberration to be corrected is calculated by adding the latest measured WF aberration and an estimated change in aberration due to pupil movement. The change of aberration is estimated as the product between the pupil displacement and the second derivative of the WF. New algorithm updates the DM according to each new pupil position. The method is tested by simulations and experimentally with an artificial eye of 7 mm pupil mounted on a translation stage and the AO-FIFC. Simulations are done with ten in vivo aberration measurements; they are shifted on y axis by a few units and the same shift is produced using the method.
The diffrence of the wavefornts represent the error of the method, which was 40±20 nm RMS in average for a 400 µm shift. Experiments done (Imagine Eyes, France) resulted in 8±3 nm RMS and 90±20 nm RMS error for 50 µm and 300 µm shift respectively.
The method provides a satisfying correction of the aberration produced by shift for 50µm which is the most probable eye shift statisticaly-according to the survey done using the pupil tracking system. The experimental result for the 300 µm shift being less likely to occur, is slightly higher than simulations, pointing an experimental error due to the set-up which shall be corrected.
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