Abstract
Purpose :
Combining AO with OCT enables ultra-high retinal image resolution and 3D visualization up to the PR level in vivo. For the first time our observational cross-sectional study tests the performance of a novel compact, multi-modal AO-imaging prototype combining AO-OCT and AO fundus camera (FC) in eyes with early and advanced dry AMD in a clinical setting.
Methods :
The AO-OCT mode generates volumetric data of the retina at 200kHz A-scan rate with a transverse resolution of 4µm and an axial resolution of 5µm. AO-OCT is acquired within a field of view of 2°x2° adjusted to focus on the PR layer at different retinal regions (drusen, geographic atrophy [GA] and intact retina) determined by AO-FC with a total recording time per volume of 0.8s. 44 eyes of 22 patients were imaged with AO-OCT/FC and spectral-domain (SD) OCT (Spectralis, Heidelberg).
Results :
En-face images from the AO-OCT volume scans were extracted by generating depth integration over PR bands to display the image on a linear amplitude scale. PR integrity was evaluated at two depths: inner/outer segment (IS/OS) junction; distal part of the OS. SD-OCT alone without AO compensation was unable to resolve individual PR. 8 eyes of 6 patients were excluded from PR analysis due to poor AO image quality, negatively affected by pupil diameter less than 7mm, cataract (LOCS III ≥ NO3/NC3, C3, P2), vitreous floaters, corneal scarring or eye movement. In 36 eyes of 20 patients AO imaging could be successfully performed. Depth integrated en-face projection over the IS/OS revealed regularly spaced reflective spots packed with a clear mosaic pattern representing cone PR in areas with intact retina in a total of 40 regions sampled over 30 eyes (40R/30E) and directly above drusen (42R/32E). In zones with GA the PR mosaic was absent at the level of the IS/OS (6R/6E). En-face projection views at the level of end tips of PR (ETPR) revealed a rich cone OS mosaic in areas of intact retina (40R/30E), however, a rarefied cone pattern over drusen (42R/32E) and missing ETPR in GA areas (6R/6E).
Conclusions :
We report the first successful application of a compact AO-OCT/FC in a routine clinical setting, which in contrast to conventional OCT offers insights into PR physiology, thereby enhancing our understanding of AMD pathogenesis as well as supporting multimodal image interpretation.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.