Capturing fine retinal structure using adaptive optics optical coherence tomography (AOOCT) with real-time retinal tracking

Abstract

Purpose : Our goal is to develop an AOOCT that is compact, easy to use, and has a resolution comparable to existing research-grade AOOCTs. In clinical fields, AOOCT has strong potentials for capturing fine retinal structures and revealing microscopic blood flows by applying angiography methods. However, commercialization of AOOCT is hindered by its high cost and large size. Furthermore, stabilization during the cell-level imaging is crucial for registration of images to construct a 3D image. Here we present an AOOCT prototype that can lead to a solution to these difficulties by using a compact optical system and real-time retinal tracking.

Methods : We designed and built a compact optical system (30*40cm) with a reference unit (20*30cm), which can take AOOCT and AOSLO images simultaneously. The horizontal resolution is 3um and the focusing range is -12D to +7D. The field of view is up to 1.5*1.5mm, and it can steer within 3mm square. A spectrometer unit from commercially available OCT allows us to achieve an axial resolution of 3.4μm with reduced cost. AOSLO images are used for real-time tracking to stabilize the imaging location with cell-level precision. The system has a multi focusing system to increase tracking stability. AOSLO and AOOCT data are used for constructing final images in post processing. We imaged healthy subjects to evaluate its performance.

Results : We achieved a resolution sufficiently high to resolve cones at 0.3-deg from the center of the fovea. The ocular aberrations were reduced well below 100nm RMS. The AOSLO tracking decreased the effect of eye motion to 1~3μm RMS and the tracking remained stable while the AOOCT focus was changed between the retinal layers. A custom-made software constructed precise registered 3D AOOCT images and it could visualize cones and even rods and RPEs in some cases. Some narrow capillaries could be seen in AOOCT images, which could not be resolved in normal OCTA.

Conclusions : This work demonstrates the performance of the AOOCT prototype. Our AOOCT is approaching the performance of research-grade AOOCTs with a compact optical system, which can be installed small laboratories and clinics. AOSLO real-time tracking allows post-processing software to construct fine 3D AOOCT images to visualize retinal structures such as cones, RPEs and blood flows, which are important for earlier detection of diseases and evaluating treatments.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.