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Rainer A Leitgeb, Laurin Ginner, Abhishek Kumar; Sensorless coherent aberrometry by PSF de-scanning with swept source OCT. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5068.
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© ARVO (1962-2015); The Authors (2016-present)
We introduce a wavefront sensorless technique to measure the wavefront error of the human eye using pencil beam swept source OCT at 1060nm wavelength in combination with digital adaptive optics.
A static pencil beam illumination swept source OCT device at 1060nm operatig at 100kHz sweep rate is used with de-scanning of the backscattered point spread function in detection. The detection channel employes a large aperture to acquire all aberrations from the ocular media. The sensorless wavefront reconstruction is performed digitally in post processing using a subaperture based algorithm. The partially coherent detection of the point-spread function (PSF) allows localizing wavefront error calculation in depth (e.g. nerve fibers or the photoreceptor layer). A volume rate of >10Hz enables stable wavefront reconstruction.
The proof of principle is first demonstrated by measuring a flat microbeads sample, and analyzing the wavefront error for various defocus positions. Since the detection is coherent, the point spread function can be corrected for aberrations by conjugating the phase using the reconstructed wavefront error. This yields the actual diffraction limited PSF of our system of 6.1µm. We performed further in-vivo measurements on healthy volunteers. A selected single measurement was measured with a Topcon aberrometer to be -0.5±0.25 dpt. Based on the introduced digital wavefront sensing concept -0.41 diopter were calculated, which reproduces well the hardware based reference measurement. Figure 1 shows the acquired PSF at the human retina in-vivo with the corresponding improvement of the PSF by phase conjugtion together with the measured wavefront error. Further in-vivo measurements are presented that reproduce well the hardware based system, but with the advantage of coherent depth control and the high sensitivity of swept source OCT.
We demonstrate a novel wavefront sensorless aberrometer approach based on Swept source OCT by de-scanning of the backscattered point spread function. The wavefront is digitally reconstructed consequently in a post processing step. The measured wavefront error reproduces well the results from a commercial Topcon wavefront aberrometer.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
(a) en-face point spread function of the depth marked with the white arrow. (b) corrected point spread function with the corresponding wavefront error (c). (d) lateral PSF after wavefront reconstruction
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