Comparison of cell size in a histologic cross section of the human retina with the resolving capability of the major types of retinal imaging modalities with and without AO. The width and length of the blue cylinders and bicone denote the transverse and axial resolutions of the instruments. Examples shown include commercial SLO, AO-SLO, AO flood illumination, commercial OCT, UHR-OCT, and UHR-AO-OCT. GCL, ganglion cell layer; IPL, inner plexiform layer; INL, inner nuclear layer; OPL, outer plexiform layer; ONL, outer nuclear layer; PL, photoreceptor layer; RNFL, retinal nerve fiber layer. The histologic cross section is from Boycott BB, Dowling JE, Kolb H. Organization of the primate retina: light microscopy. Philos Trans R Soc Lond B. 1969;255:109–184, © 1969, by permission of the Royal Society.