Abstract
Purpose :
We demonstrate a new holographic line field en-face OCT system using digital adaptive optics (DAO). The system achieves en-face frame rates up to 100 Hz, enabling digital adaptive optics to compensate for defocus and aberrations. High-resolution en-face images were acquired in healthy volunteers showing cellular retinal details.
Methods :
High resolution en-face images were acquired with an off axis holographic line field en-face OCT system with a Field of View (FOV) of 4x2°. An off axis angle between sample and reference arm introduce a spatial modulation of the interference signal. This enables to filter the structure carrying interference terms and reconstruct the OCT en-face image. Standard B-scan imaging is achieved by scanning the reference arm. The confocal and coherence gate can then be set individually, due to the possibility of digitally refocusing structures outside the confocal range can be visualized. Further the fast recording of single lines of up to 100kHz allows to calculate en-face Doppler OCT velocity maps in small retinal vessels. Furthermore, speckle analysis between successive en-face planes allows for intensity based en-face OCT-Angiography.
Results :
High resolution en-face images were acquired from a healthy volunteer. Different layers were selected by tuning the reference arm. To validate the imaging performance images at the nerve fiber layer, the photoreceptor layer as well as the outer plexiform layer are recorded. Using DAO, defocus and higher order aberrations were compensated enabling a better definition of cellular structures, such as the photoreceptors. Recording en-face videos with high-speed frame rate reveals the direction of circulating read blood cells within small capillaries. With en-face Doppler flow calculation, flow velocities down to ±56 µm/s can be detected. This enables quantifying flow even within micro capillaries in-vivo.
Conclusions :
En-face line field OCT is a good tool for fast single layer assessments in high resolution. It enables to implement DAO for defocus and higher order aberrations correction to reveal cellular details without hardware adaptive optics. Further the en-face Doppler flow can be calculated yielding important information on retinal blood supply in addition to the vascular structure. The fast imaging rate has the potential to study fast physiologic processes in-vivo.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.