Abstract
Purpose :
Ocular aberrations result in decreased detection sensitivity in FFOCT, posing challenges for inner retinal imaging. To explore the highest sensitivity possible in FFOCT, we have developed a FFOCT system combined with adaptive optics (AO), allowing for high-resolution (2 μm×2 μm×8 μm) retinal images over a wide field-of-view (FOV) of 5°.
Methods :
The FFOCT comprises a LED (850 nm, M850L3, Thorlabs) and a 2D camera (Adimec). A spectral domain OCT (Thorlabs) was coupled to the FFOCT for three reasons: 1) track retinal axial motion; 2) position the FFOCT coherent gate at the retinal layer of interest; 3) serve as wavefront sensor beacon for AO.
A pupil-conjugated DM was implmented in the sample arm.
Image sequences composed of 300 frames were acquired at 500 Hz in FFOCT.
Results :
Figure 1 demonstrates a dual-channel wavefront optimization at the photoreceptor layer (PRL) at the foveal center.
In SDOCT, a better visualization of cells was attained after AO correction. In FFOCT, without aberration correction, cones could be resolved up to 1.3°, highlighting the robustness of FFOCT lateral resolution for low-order aberrations. After the wavefront optimization, it allowed for the visualization of cones up to 0.3° close to the fovea, as well as a twofold increase in SNR.
The performance of depth-resolved wavefront optimization from inner retina to outer retina is shown in Fig.2. Thanks to high axial resolution of 8 μm and aberration correction, Figure 2a showed enhanced SNR from 16 dB to 29 dB, enabling the visualization of fine inner retina features: micron-sized hyper-reflective spots along the axon bundles, small vessels and vessel wall. The optimized PRL showed well-resolved photoreceptors (Fig. 2b).
The combination of FFOCT with sensor-based AO, enabled us to acquire high-resolution FFOCT images over the entire 5° FOV without apparent anisoplanatism.
Conclusions :
In this work, we implemented a lens-based AO-FFOCT system, giving the first successful application of sensor-based AO for wavefront correction in time-domain FFOCT. The results demonstrated enhanced resolution and SNR after AO correction, enabling high performance in foveal imaging and also inner retina layers in a wide FOV.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.