of the fovea is the foveola – about 0.35 mm in diameter – or central pit where only cone photoreceptors are present and there are virtually no rods. The central fovea consists of very compact cones, thinner and more rod-like in appearance than cones elsewhere. These cones are very densely packed (in a hexagonal pattern). Starting at the outskirts of the fovea, however, rods gradually appear, and the absolute density of cone receptors progressively decreases. In 2018 the anatomy of the foveola was reinvestigated, and it was discovered that outer segments from the central foveolar cones of monkeys are not straight and twice as long as those from the parafovea. Size The size of the fovea is relatively small with regard to the rest of the retina. However, it is the only area in the retina where 20/20 vision is attainable, and is the area where fine detail and colour can be distinguished. Properties Anatomical macula / macula lutea / area centralis (clinical: posterior pole): Diameter = 5.5mm (~3.5 disc-diameters) (about 18 deg of VF) Demarcated by the superior and inferior temporal arterial arcades. Has an elliptical shape horizontally. Histologically the only region of the retina where GCL has >1 layer of ganglion cells Yellowish appearance = luteal pigments (xanthophyll and beta-carotenoid (beta-carotene) in the outer nuclear layers inward. Anatomical perifovea: Region between parafovea (2.5mm) and edge of macula GCL has 2–4 layers of cells. 12 cones / 100 um Anatomical parafovea: Diameter = 2.5mm. GCL has >5 layers of cells, and highest density of cones Anatomical fovea / fovea centralis (clinical: macula) Area of depression in the centre of the macula lutea. Diameter = 1.5mm (~1 disc-diameter) (about 5 deg of VF) Foveal avascular zone (FAZ) Diameter = 0.5mm (about 1.5 deg of VF) Approximately equal to the foveola Anatomical foveola (clinical: fovea) Diameter = 0.35mm (about 1 deg of VF) the central floor of depression of fovea centralis 50 cones / 100 um Highest visual acuity Anatomical umbo Represents the precise center of the macula Diameter = 0.15mm Corresponds to the clinical light reflex Function In the primate fovea (including humans) the ratios of ganglion cells to photoreceptors is about 2.5; almost every ganglion cell receives data from a single cone, and each cone feeds onto between one and 3 ganglion cells. Therefore, the acuity of foveal vision is limited only by the density of the cone mosaic,