We provide a proof of concept for the detailed characterization of retinal capillary features and surrounding photoreceptor mosaic using a customized nonadaptive optics angiography imaging system.
High-resolution fluorescein angiography (FFA) and/or indocyanine green angiography (ICGA) images were obtained using a modified Heidelberg retina angiograph (HRA2) device with a reduced scan angle enabling 3° field of view. Colocalized images of the photoreceptor mosaic also were captured in vivo using the same instrument. Visibility of vascular subbranches were compared between high-resolution images and conventional fundus angiography (FA) with a 30° field of view.
High-resolution angiographic and infrared images (3° × 3° field of view, a 10-fold magnification) were obtained in 10 participants. These included seven patients with various retinal diseases, including myopic degeneration, diabetic retinopathy, macular telangiectasia, and central serous chorioretinopathy, as well as three healthy controls. Images of the retinal vasculature down to the capillary level were obtained on angiography with the ability to visualize a mean 1.2 levels more subbranches compared to conventional FA. In addition, imaging of the photoreceptor cone mosaic, to a sufficient resolution to calculate cone density, was possible. Movement of blood cells within the vasculature also was discernible on infrared videography.
This exploratory study demonstrates that fast high-resolution angiography and cone visualization is feasible using a commercially available imaging system.
This offers potential to better understand the relationship between the retinal neurovascular system in health and disease and the timing of therapeutic interventions in disease states.