Abstract
Purpose :
Adaptive Optics (AO) ophthalmoscopes have become the primary technique to image individual retinal neurons in the living human retina with clinical and basic science value. However, AO comes at the price of a limited field-of-view (FOV) and complex, expensive and cumbersome hardware, strongly limiting clinical deployment. Here, we introduce Adaptive-Glasses Full-Field OCT (FFOCT) retinal imaging system allying high-resolution, high frame rate (300Hz), 1mm FOV in a very compact system.
Methods :
We used our retinal imaging system combining time-domain FFOCT, with a spatially incoherent light source and axial motion correction, and SDOCT. We previously demonstrated the capacity of this system to achieve foveal cone mosaic imaging without the use of AO, owing to the low sensitivity to ocular aberrations of the FFOCT, mostly affecting the signal to noise ratio (SNR). To increase the SNR, we implemented a novel AO design named Adaptive Glasses approach, consisting of positioning an adaptive lens (AL) in front of the eye, like prescribed eyeglasses. The AL is driven by a wavefront sensorless algorithm based on the SD-OCT signal level. Enlarged FOV was made possible by optically shaping the FFOCT coherence gate geometry to match the retinal curvature.
Results :
The FFOCT SNR was enhanced up to a factor of 10 by using the AL for a dilated pupil. The coherence gate shaping allowed for retinal images with a 1-mm FOV, good consistency, and repeatability. The resolution within the wide-FOV was not affected by the eye's isoplanatic patch, a fundamental limitation of AO-systems, highlighting the FFOCT low-sensitivity to ocular aberrations. As SDOCT cross-section and FFOCT en-face images are simultaneously acquired and displayed in real-time, both had its image quality improved. We used the AL to adjust the focus axial position within the retina, to image structures in the inner retina as the nerve fiber layer with an 8 µm axial resolution.
Conclusions :
We presented an AO-OCT system allying a useful 1mm FOV, high cellular resolution in all three dimensions and high frame rate for a given retinal plane, all these features in a very compact system. The relative simplicity and low-cost of the FFOCT imaging technique compared to current AO-assisted ophthalmoscopes may pave the way towards the adoption of FFOCT as a routine clinical imaging system.
This is a 2020 Imaging in the Eye Conference abstract.