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Sang Hyuck Lee, Yifan Jian, Robert Zawadzki, John Werner; Improved cellular resolution retinal imaging with aberration free and pupil wander free reflective Adaptive Optics - Optical Coherence Tomography Imaging System. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1511.
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© ARVO (1962-2015); The Authors (2016-present)
Implementation of aberration free and pupil wander free optical design is critical for achieving optimum performance of Adaptive Optics (AO) system and for measuring and correcting aberration of the sample, in our case subject’s ocular aberrations. Wavefront error is directly related to the final performance of image, so we should minimize it. Pupil wonder has negative effect on performance of AO system. Because the different parts of eye pupil blurs measured wavefronts. Our purpose is to test our new reflective aberration free and pupil wander free AO - Optical Coherence Tomography (OCT) system for retinal imaging.
In our 1st generation AO-OCT system, the mirrors were placed sequentially in one plane. As a result, the off-axis aberrations were increasing when we added each mirrors and the final wavefront error became much larger than the diffraction limit. In our 2nd generation AO-OCT system, design with minimum residual aberrations and pupil wander, mirrors were placed non-sequentially and were placed out of the single plane, so that the aberrations can be counterbalanced from the corresponding aberration canceling mirrors. Our new system performance was tested on imaging of volumetric morphology of photoreceptors (both cones and rods) on healthy subjects. We used SFU BORG GPU-based OCT data acquisition software.
The initial wavefront aberration of our new system for 3° x 3° FOV is suppressed under 10nm which is much lower than that of the 1st Gen. AO-OCT system, 230nm. We used optical design software (Zemax) for the simulation. And the maximum pupil wander of 2nd generation system for 3° x 3° FOV is under 0.1mm which is also lower than the value of the previous system, 0.43mm. Images of photoreceptor layers extracted from volumetric scans show improved resolution and contrast if compared to the ones acquired with 1st Gen. AO-OCT system.
Off-axis AO-OCT system was designed and successfully implemented allowing minimization of the wavefront error and the pupil wander allowing better resolution and image quality of retina layers. Increased lateral resolution allows studying of 3D morphology of Cone and Rod photoreceptors mosaics.
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