Abstract
Purpose :
Adaptive optics line-scan OCT offers high speed, resolution and sensitivity for imaging retinal structure and function. Here we report its implementation with reflective mirror based telescopes, optimized for improved resolution of fast light-induced retinal activity and weak retinal reflections.
Methods :
Two wavelength bands from a supercontinuum light source were used for illumination - OCT (λ: 820 ± 40 nm) and line-scan ophthalmoscope (λ: 750±6 nm), while a superluminescent diode (λ: 980±10 nm) was used for wavefront sensing. A cylindrical lens created a linear illumination at the entrance pupil. In the sample arm, the entrance pupil was optically conjugated to a 1D galvo scanner, deformable mirror and the eye’s pupil via three spherical-mirror telescopes. In the reference arm, the OCT beam was propagated via three spherical-mirror telescope relays to minimize the diffraction resulting from the 8.5 meter long travel, intended to match the sample arm optical path length. Non-planar telescope folding was followed and Zemax optimization was performed for the entire optical design, including the sample, reference and detection arms. In detection, band-pass filters separated OCT, LSO and wavefront sensing channels. An anamorphic telescope composed of two positive cylindrical lenses enabled efficient optimization of spatial and spectral resolution simultaneously in detection. The system’s performance was assessed by imaging the structure of foveal cones, retinal ganglion cells and the functional response of parafoveal cones to a 660 nm flash stimulus.
Results :
Over a 2.2 deg field-of-view and 3.2 D vergence range, the system’s optical performance was optimized to remain under the diffraction-limit. The anamorphic configuration significantly improved signal collection efficiency and roll-off. Cones at ~0.2 deg from the foveal center, and retinal ganglion cells at 10 deg eccentricity were resolved in the OCT en face images. The temporal evolution of phase difference between individual cone inner/outer segment junction and outer segment tips provided a measure of light-induced activity in cones and was resolvable at ~0.2 deg. eccentricity from the foveal center.
Conclusions :
We implemented the first reflective mirror-based line-scan OCT and demonstrated its feasibility for foveal cone optoretinography and visualizing retinal ganglion cell structure.
This is a 2021 ARVO Annual Meeting abstract.