Optical Coherence Tomography (OCT) has revolutionized modern ophthalmology, providing depth resolved images of the retinal layers in a system that is suited to a clinical environment. A limitation of the performance and utilization of the OCT systems has been the lateral resolution. Through the combination of wavefront sensorless adaptive optics with dual variable optical elements, we present a compact lens based OCT system that is capable of imaging the photoreceptor mosaic. We utilized a commercially available variable focal length lens to correct for a wide range of defocus commonly found in patient eyes, and a multi-actuator adaptive lens after linearization of the hysteresis in the piezoelectric actuators for aberration correction to obtain near diffraction limited imaging at the retina. A parallel processing computational platform permitted real-time image acquisition and display. The Data-based Online Nonlinear Extremum seeker (DONE) algorithm was used for real time optimization of the wavefront sensorless adaptive optics OCT, and the performance was compared with a coordinate search algorithm. Cross sectional images of the retinal layers and en face images of the cone photoreceptor mosaic acquired in vivo from research volunteers before and after WSAO optimization are presented. Applying the DONE algorithm in vivo for wavefront sensorless AO-OCT demonstrates that the DONE algorithm succeeds in drastically improving the signal while achieving a computational time of 1 ms per iteration, making it applicable for high speed real time applications.
Hans R. G. W. Verstraete, Morgan Heisler, Myeong Jin Ju, Daniel J. Wahl, Laurens Bliek, Jeroen Kalkman, Stefano Bonora, Marinko V. Sarunic, Michel Verhaegen, and Yifan Jian, "Real time optimization algorithm for wavefront sensorless adaptive optics OCT (Conference Presentation)," Proc. SPIE 10073, Adaptive Optics and Wavefront Control for Biological Systems III, 100731B (Presented at SPIE BiOS: January 30, 2017; Published: 24 April 2017); https://doi.org/10.1117/12.2252732.5380600115001.
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