Title: S-OCT and OCT-A in dry AMD and GA
The high speed, deep penetration, and high sensitivity of swept source OCT allows excellent and consistent visualization of the outer retina and choroid, which are the structures most relevant to the development and progression of atrophic AMD. Several OCT risk factors for the development of atrophy and late AMD have been identified including intra-retinal hyper-reflective foci, drusen with hyporeflective cores, high drusen volume, subretinal drusenoid deposits, and a thin choroid. The high speed of swept source OCT facilitates the generation of high-resolution on en face images. This allows depiction of the topography of these important features associated with dry AMD, and facilitates their quantification as well as the quantification of geographic atrophy. In addition, swept source OCT Angiography provides superior visualization of the choriocapillaris (CC), particularly underlying drusen. In a study of GA eyes images with the Triton OCT-A, we observed partial preservation of the CC within the bed of atrophy. We also observed more signal voids adjacent to the atrophy compared to more distant areas (35.6% vs 33.9%). In addition, we observed a reduction if CC flow density and an increase in CC flow void area underlying drusen compared to surrounding areas. Taken together these findings highlight the importance of studying the choriocapillaris with swept source OCT-A, which may provide new insights into atrophic AMD pathophysiology.