Fig. 2

Scanning laser ophthalmoscopy (SLO) confocal apertures for reflectance (direct-mode) and retroillumination (indirect-mode) SLO imaging. A In standard reflectance imaging, a centered confocal aperture limits light collection only to photons reflected “directly” back to the photodetector from the illuminated retinal spot, [25] thereby increasing retinal image contrast by blocking photons from other fundus locations that could cause veiling glare at the photodetector. [25, 64] B and C. In retroillumination imaging, an aperture deviated laterally (B) or an annular aperture (C) blocks retroreflected light and collects only photons scattered “indirectly” back to the SLO’s photodetector. Laterally-deviated (B) or annular (C) apertures assure asymmetric or symmetric light collection in the retinal plane, respectively. In the Mirante system, asymmetric retroillumination imaging (B) transilluminates, highlights and shades borders of imaged chorioretinal structures whereas symmetric annular (ring) aperture light collection (C) provides low contrast transillumination images