Establishing New Benchmarks for Measuring Progression of Macular Degeneration
The purpose of our Network grant is to use optical coherence tomography angiography (OCT-A) and adaptive optics scanning laser ophthalmoscopy (AOSLO) to better understand what causes visual loss in age-related macular degeneration (AMD). OCT-A images the outer retinal blood supply, the choriocapillaris, which atrophies in advanced AMD. AOSLO provides high-resolution visualization of photoreceptors that are damaged in advanced AMD. By imaging the choriocapillaris and overlying macular retina, we hypothesize we can determine whether visual loss in AMD is primarily due to vascular disease, or alternatively, is caused by a primary cellular degeneration. Our imaging efforts have revealed striking alterations of the choriocapillaris in patients with advanced AMD. In both dry AMD with macular atrophy and in wet AMD, OCT-Areveals dramatic reductions in choriocapillaris perfusion. In macular atrophy, OCT-A shows a surrounding region of reduced choriocapillaris blood flow. Outside of this surrounding region, choriocapillaris perfusion appears normal. Similarly, in wet AMD, OCT-A reveals that there is choriocapillaris hypoperfusion bordering choroidal neovascularization. For patients with dry AMD and macular atrophy, AOSLO has shown that photoreceptor density overlying regions of reduced choriocapillaris perfusion is reduced; however, when choriocapillaris perfusion is normal, so too, is the overlying photoreceptor density. While our initial application of AOSLO imaging has been limited to visualization of photoreceptors, we are now imaging retinal pigment epithelial (RPE) cells. Because these cells are particularly susceptible to insult in the early stages of AMD, it will be interesting to see whether RPE alterations precede or result from reductions in choriocapillaris perfusion.