The<unk>  is a depression in the inner retinal surface, about 1.5 mm wide, the photoreceptor layer of which is entirely cones and which is specialized for maximum visual acuity. Within the<unk>  is a region of 0.5mm diameter called the<unk> l avascular zone (an area without any blood vessels). This allows the light to be sensed without any dispersion or loss. This anatomy is responsible for the depression in the center of the<unk> . The<unk> l pit is surrounded by the<unk> l rim that contains the neurons displaced from the pit. This is the thickest part of the retina. The<unk>  is located in a small avascular zone and receives most of its oxygen from the vessels in the choroid, which is across the retinal pigment epithelium and Bruch's membrane. The high spatial density of cones along with the absence of blood vessels at the<unk>  accounts for the high visual acuity capability at the<unk> . The center of the<unk>  is the<unk> la – about 0.35 mm in diameter – or central pit where only cone photoreceptors are present and there are virtually no rods. The central<unk>  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<unk> , however, rods gradually appear, and the absolute density of cone receptors progressively decreases. In 2018 the anatomy of the<unk> la was reinvestigated, and it was discovered that outer segments from the central<unk> lar cones of monkeys are not straight and twice as long as those from the parafovea. Size The size of the<unk>  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 Time-domain OCT of the macular area of a retina at 800 nm, axial resolution 3 µm Spectral-domain OCT macula cross-section scan Macula histology (OCT) Diagram showing the relative acuity of the left human eye (horizontal section) in degrees from the<unk>  Photograph of the retina of the human eye, with overlay diagrams showing the positions and sizes of the macula,<unk> , and optic disc * Anatomical macula / macula lutea / area<unk>  (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<unk>  /<unk>  (clinical: macula) * Area of depression in the centre of the macula lutea. * Diameter = 1.5mm (~1 disc-diameter) (about 5 deg of VF) *<unk> l avascular zone (FAZ) * Diameter = 0.5mm (about 1.5 deg of VF) * Approximately equal to the<unk> la * Anatomical<unk> la (clinical:<unk>  * Diameter = 0.35mm (about 1 deg of VF) * the central floor of depression of<unk>  * 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
Fovea centralis
Caput Medusae
Corpora quadrigemina
Caput medusae
Vesical tenesmus
Cutis verticis gyrata
Pterygium inversum unguis
Glia limitans