Abstract
Purpose :
Ocular wavefront aberrometry and anatomical imaging are both essential for vision research and clinical applications. With MHz VCSEL swept-source, we demonstrate anatomical imaging of the anterior segment of the eye and the Digital Wavefront Aberrometry (DWA) with a high dynamic range of up to 20 D using a customized design dual-mode system.
Methods :
The dual-mode system is designed to switch between swept-source OCT (SS-OCT) and DWA via a polarization optics-based switching mechanism. For the fiber-based SS-OCT, VCSEL swept-source (OCTLight) with center wavelength 1069 nm, bandwidth 33 nm, and sweep rate 1.6 MHz is used, giving an axial resolution of 15 um and lateral resolution of 35 um in air. Tomographic scans are acquired at a B-scan rate of 780 Hz. Both forward and backward sweeps are utilized to profit from the maximum available sweep rate. DWA is built in a de-scanning configuration with a static illumination spot and lateral shearing of wavefronts based on a non-iterative guide star technique used to reconstruct the wavefront as published previously in our group. In brief, a narrow beam illumination of 0.6 mm forms a diffraction-limited spot on the retina acting as a pseudo point source, and the back-reflected light from the full pupil of the eye is imaged at the detection fiber plane of the sample arm and descanned as galvo moves, enabling a single-pass point spread function (PSF) measurement. A tunable lens with focus tuning ranging > ±10 D is placed to compensate the defocus term before the detection fiber, to further expand the measurement range. An artificial eye with a selected pupil size of 6 mm and defocus ranging ±10 D is imaged for proof of concept. The anterior segment of a volunteer eye is imaged as well as its aberration.
Results :
DWA is limited by the SNR drop caused by the highly defocused PSF. With the aid of a tunable lens to pre-compensate the defocus, we can expand the defocus dynamic range to up to 20 D, compared to the previous 4 D measurement range. Fast anterior segment OCT imaging with a B-scan rate of 780 Hz is done utilizing the MHz swept source.
Conclusions :
We demonstrate the wide dynamic range DWA and fast anterior segment OCT imaging, this research, and clinically insightful approach may potentially apply to the individual treatment plan for better refractive surgery and cataract outcomes.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.