Abstract
Purpose :
A high-speed full-field (FF) swept-source (SS) optical coherence tomography (OCT) was implemented incorporating an adaptive optics (AO) subsystem to image the human retina in vivo. It has been previously reported that digital aberration correction (DAC) permits visualization of cones with FF-SS-OCT, but only in the perifovea and periphery. By combining hardware AO with FF-SS-OCT this system is able to resolve foveal cones and measure their functional responses. With the reference arm blocked, the system is a high speed (kHz) AO flood illumination (FI) fundus camera.
Methods :
The FF-SS-OCT imaging system is arranged as a Mach-Zehnder interferometer with tunable source (Superlum BS-840-2-HP). In the sample arm the light that is backscattered from the retina is imaged at a CMOS sensor (Photron NOVA S12 Fastcam). The reference arm hits the camera with an angle of ≈ 1○ with respect to the sample arm to suppress common path artifacts. In parallel, a deformable mirror (ALPAO DM-97-15) is operated by custom software in closed-loop with a Hartmann-Shack wavefront sensor for real-time aberration correction. The system also incorporates a stimulus channel based on a green (555 nm) LED, used to elicit optoretinographic (ORG) responses. Two subjects were imaged at eccentricities between 1○ and 2○TR.
Results :
With closed-loop AO correction, diffraction-limited FI and OCT images of the retina were successfully collected at rates of 1 kHz and 200-1000 Hz, respectively. Cones were laterally resolved in the FI images and resolved in 3D in the OCT images. ORGs were collected at 2○TR and 200-400 vol/s, showing a characteristic, stimulus-evoked pattern of initial rapid contraction followed by slower elongation of the outer segment, similar to what was previously reported by others using FF-OCT in the periphery or confocal scanning AO-OCT in the fovea.
Conclusions :
The system was demonstrated to be capable of producing multimodal images and measuring ORG responses in the foveal cone mosaic. Future plans include incorporation of a DMD-based visible stimulus channel and modification of the AO system to permit higher correction speed and dynamic range. Comparison of images acquired with AO with images acquired with DAC is also of interest.
This is a 2021 ARVO Annual Meeting abstract.