Cellular Resolution in vivo Retinal Imaging with Motion Artifact-Free Adaptive Optics - Optical Coherence Tomography

Abstract

Purpose: : To test the feasibility of new instrumentation that reduces retinal motion artifacts present in volumetric data sets acquired with cellular resolution adaptive optics - Fourier-domain optical coherence tomography (AO-OCT) for improved visualization of microscopic retinal structures.

Methods: : An ultra-high-resolution AO-OCT system was combined with an adaptive optics scanning laser ophthalmoscope (AO-SLO) to track retinal motion during in-vivo AO-OCT data acquisition. Both systems share a common AO sub-system and vertical scanner to permit simultaneous acquisition (at 27 frames/s) of retinal images from the two channels. Transverse eye motion was reconstructed from AO-SLO videos, and a motion adjustment vector was assigned to each AO-OCT A-scan to create motion artifact-free retinal volumes. Next, multiple volumes were averaged to reduce speckle contrast present on single B-scans to improve the visibility of microscopic structures in the inner retina.

Results: : Averaged motion-corrected AO-OCT volumes were created for healthy volunteers. For comparison, AO-OCT volumes acquired with a CMOS-based high speed (125 frames/s) stand alone AO-OCT instrument were also acquired at the same eccentricities for the same subjects.

Conclusions: : Eye motion artifacts limit resolution of AO-OCT retinal imaging due to high magnification. Distortion of volumetric structures also restricts the value of image averaging to reduce speckle contrast in OCT data sets. Correction of retinal motion artifacts allows successful application of this image-processing step in AO-OCT. Additionally, motion artifact-free retinal volumes permit monitoring and quantification of retinal structures at the cellular scale. Finally, motion-corrected AO-OCT volumes acquired at standard speed offer an interesting alternative to ultra-high-speed AO-OCT volume acquisition, as the latter method may suffer from insufficient instrument sensitivity to visualize all the retinal structures, especially cells in the inner retina.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • retina • optic nerve