Editing Macula (section)

==Structure==
[[File:Macula.svg|thumb|Photograph of the retina of the human eye, with overlay diagrams showing the positions and sizes of the macula, fovea, and optic disc]]
[[File:Macula lutea.svg|thumb|upright|Schematic diagram of the macula lutea of the retina, showing perifovea, parafovea, fovea, and clinical macula]]

The macula is an oval-shaped pigmented area in the center of the [[retina]] of the [[human eye]] and other animal [[eye]]s. Its center is shifted slightly away from the [[optical axis]] (laterally, by 5°=1.5&nbsp;mm).<ref name="leGrand">{{cite book |last= le Grand |first= Yves |date= 1957 |title= Light, colour and vision |location= London |publisher= Chapman & Hall |page= 52 }}</ref>
The macula in humans has a diameter of around {{convert|5.5|mm|abbr=on}} and is subdivided into the [[umbo (eye)|umbo]], [[foveola]], [[foveal avascular zone]], [[Fovea centralis|fovea]], [[parafovea]], and [[perifovea]] areas.<ref name="Project Orbis International"/>
An even smaller central region of highest receptor density (40–80 μm) is sometimes referred to as the ''foveal bouquet''.<ref name="oesterberg">{{cite journal | last1 = Oesterberg | first1 = G. | title = Topography of the layer of rods and cones in the human retina | journal = Acta Ophthalmologica Supplement | volume = 6–10 | year = 1935 | pages = 11–96}}</ref><ref name="Polyak">{{cite book |last= Polyak |first= S. L.|date= 1941|title= The Retina |location= Chicago|publisher= University of Chicago Press}}</ref><ref name="tyler_hamer">{{cite journal | last1 = Tyler | first1 = C.W. | last2 = Hamer | first2 = R.D. | title = Analysis of visual modulation sensitivity. IV. Validity of the Ferry-Porter law.| journal = Journal of the Optical Society of America A | volume = 7 |issue=4 |  year = 1990 | pages=743–758| doi = 10.1364/JOSAA.7.000743 | pmid = 2338596 | bibcode = 1990JOSAA...7..743T }}</ref><ref name="myths">{{cite journal | last1 = Strasburger | first1 = Hans | title = Seven myths on crowding and peripheral vision | journal = i-Perception| volume = 11 |issue=2 |  year = 2020 | pages=1–45| doi = 10.1177/2041669520913052 | pmid = 32489576 | pmc = 7238452 |url = https://doi.org/10.1177/2041669520913052}}</ref>
The anatomical macula at {{convert|5.5|mm|abbr=on}} is much larger than the clinical macula which, at {{convert|1.5|mm|abbr=on}}, corresponds to the anatomical fovea.<ref name="Yanoff2009"/><ref name="Small1994"/><ref name="PeymanMeffert2000"/>

The clinical macula is seen when viewed from the pupil, as in [[ophthalmoscopy]] or [[retinal photography]]. The anatomical macula is defined [[Histology|histologically]] in terms of having two or more layers of [[retinal ganglion cell|ganglion cell]]s.<ref name="Remington2011">{{cite book|last=Remington|first=Lee Ann|title=Clinical Anatomy of the Visual System|url=https://books.google.com/books?id=Bhf0Fpvq9GMC&pg=PT314|access-date=7 November 2014|year= 2011|publisher=Elsevier Health Sciences|isbn=978-1-4557-2777-3|pages=314–315}}</ref>  The umbo is the center of the foveola which in turn is located at the center of the fovea.

The fovea is located near the center of the macula.  It is a small pit that contains the largest concentration of [[cone cell]]s.  The retina's receptor layer contains two types of photosensitive cells, the [[rod cell]]s and the cone cells.

===Color===
Because the macula is yellow in color, it absorbs excess blue and ultraviolet light that enter the eye and acts as a natural sunblock (analogous to sunglasses) for this area of the retina. The yellow color comes from its content of [[lutein]] and [[zeaxanthin]], which are yellow [[xanthophyll]] [[carotenoid]]s, derived from the diet. Zeaxanthin predominates at the macula, while lutein predominates elsewhere in the retina. There is some evidence that these carotenoids protect the pigmented region from some types of [[macular degeneration]]. A formulation of 10&nbsp;[[Milligrams|mg]] lutein and 2&nbsp;mg zeaxanthin has been shown to reduce the risk of age-related macular degeneration progressing to advanced stages, although these carotenoids have not been shown to prevent the disease.<ref name="pmid25709776">{{cite journal | author=Hobbs RP, Bernstein PS | title=Nutrient Supplementation for Age-related Macular Degeneration, Cataract, and Dry Eye | journal=Journal of Ophthalmic and Vision Research | volume=9 | issue=4 | year=2014 | pages=487–493 | doi=10.4103/2008-322X.150829 | pmid=25709776 | pmc=4329711 | doi-access=free }}</ref>

After death or [[Enucleation of the eye|enucleation]] (removal of the eye), the macula appears yellow, a color that is not visible in the living eye except when viewed with light from which red has been filtered.<ref name="BrittonLiaaen-Jensen2009">{{cite book|last1=Britton|first1=George|last2=Liaaen-Jensen|first2=Synnove|author-link2=Synnøve Liaaen Jensen|last3=Pfander|first3=Hanspeter|title=Carotenoids Volume 5: Nutrition and Health|url=https://books.google.com/books?id=c8USiLi73dUC&pg=PA301|access-date=7 November 2014|date= 2009|publisher=Springer Science & Business Media|isbn=978-3-7643-7501-0|page=301}}</ref>

===Regions===
* [[Fovea centralis|Fovea]] – {{convert|1.55|mm|abbr=on}}
* [[Foveal avascular zone]] (FAZ) – {{convert|0.5 to 0.6|mm|abbr=on}}
* [[Foveola]] – {{convert|0.35|mm|abbr=on}}
* [[Umbo (eye)|Umbo]] – {{convert|0.15|mm|abbr=on}}