{{Short description|Dark ring around the iris of the eye}} {{Distinguish|Kayser–Fleischer ring|}} thumb|Prominent limbal ringA '''limbal ring''' is a dark ring around the iris of the eye, where the sclera meets the cornea.<ref name=":1">{{cite patent |country=United States |number=US7246903B2 |assign=Johnson and Johnson Vision Care Inc. |title=Tinted contact lenses with combined limbal ring and iris patterns |pubdate=24 July 2007 |url=http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&p=1&u=/netahtml/PTO/srchnum.html&r=1&f=G&l=50&d=PALL&s1=7246903.PN }}{{Dead link|date=November 2025 |bot=InternetArchiveBot }}</ref> It is a dark-colored manifestation of the corneal limbus resulting from optical properties of the region.<ref name=pmid196488422>{{cite journal |last1=Shyu |first1=Betsy P. |last2=Wyatt |first2=Harry J. |year=2009 |title=Appearance of the human eye: Optical contributions to the 'limbal ring' |journal=Optometry and Vision Science |volume=86 |issue=9 |pages=E1069–E1077 |doi=10.1097/OPX.0b013e3181b4f010 |pmid=19648842 |s2cid=39174174 }}</ref> The appearance and visibility of the limbal ring can be negatively affected by a variety of medical conditions concerning the peripheral cornea.<ref name=":0">{{cite journal |vauthors=Peshek D, Semmaknejad N, Hoffman D, Foley P |year=2011 |title=Preliminary evidence that the limbal ring influences facial attractiveness |journal=Evolutionary Psychology |volume=9 |issue=2 |pages=137–146 |doi=10.1177/147470491100900201 |doi-access=free |pmid=22947961 |url=https://escholarship.org/content/qt0964610k/qt0964610k.pdf?t=nfa9wu }}</ref> It has been suggested that limbal ring thickness may correlate with health or youthfulness and may contribute to facial attractiveness.<ref name=":0"/><ref name=pmid28978250/> The thickness of the limbal ring varies by pupil dilation: When the pupil is larger, the limbal ring narrows.<ref>{{cite journal |last=Shyu |first=Betsy P. |last2=Wyatt |first2=Harry J. |date=September 2009 |title=Appearance of the human eye: Optical contributions to the "limbal ring" |journal=Optometry and Vision Science |volume=86 |issue=9 |pages=E1069–E1077 |doi=10.1097/OPX.0b013e3181b4f010 |issn=1040-5488 |lang=en |url=https://journals.lww.com/00006324-200909000-00007 |url-access=subscription }}</ref> Some contact lenses are colored to simulate limbal rings.<ref name=":1"/>
==Youth, health, and attractiveness== thumb|Blue eye without a limbal ring
Both health and youth are positively correlated with a prominent limbal ring.<ref name=":02">{{cite journal |vauthors=Peshek D, Semmaknejad N, Hoffman D, Foley P |year=2011 |title=Preliminary evidence that the limbal ring influences facial attractiveness |journal=Evolutionary Psychology |volume=9 |issue=2 |pages=137–146 |doi=10.1177/147470491100900201 |doi-access=free |pmid=22947961 |url=https://escholarship.org/content/qt0964610k/qt0964610k.pdf?t=nfa9wu }}</ref> For instance, a darker limbal ring tends to be found more attractive than the absence of a limbal ring, suggesting that both sexes "use the limbal ring as a probabilistic indicator of reproductive fitness".<ref name=":02"/> Furthermore, limbal rings appear to be most noticeable "for individuals relatively free from chronic health issues".<ref name=pmid28978250>{{cite journal |vauthors=Brown M, Sacco DF | year=2018 |title=Put a (limbal) ring on it: Women perceive men's limbal rings as a health cue in short-term mating domains |journal=Personality and Social Psychology Bulletin |volume=44 |issue=1 |pages=80–91 |doi=10.1177/0146167217733072 |doi-access= |pmid=28978250 }}</ref>
The limbal ring is thought to contain corneal epithelium stem cells.<ref>{{cite journal |last1=Li |first1=De-Quan |last2=Chen |first2=Zhuo |last3=Song |first3=Xiu Jun |last4=de Paiva |first4=Cintia S. |last5=Kim |first5=Hyun-Seung |last6=Pflugfelder |first6=Stephen C. |date=April 2005 |title=Partial enrichment of a population of human limbal epithelial cells with putative stem cell properties based on collagen type IV adhesiveness |journal=Experimental Eye Research |volume=80 |issue=4 |pages=581–590 |doi=10.1016/j.exer.2004.11.011 |issn=0014-4835 |pmc=2906384 |pmid=15781286 }}</ref> Diseases involving a limbal stem cell deficiency are associated with blindness, as those with such deficiencies are "unable to maintain a stable corneal surface".<ref>{{Cite journal |last1=James |first1=S. Elizabeth |last2=Rowe |first2=Andrea |last3=Ilari |first3=Luca |last4=Daya |first4=Sheraz |last5=Martin |first5=Robin |date=July 2001 |title=The potential for eye bank limbal rings to generate cultured corneal epithelial allografts |journal=Cornea |volume=20 |issue=5 |pages=488–494 |issn=0277-3740 |doi=10.1097/00003226-200107000-00010 |pmid=11413404 |s2cid=21296292 |lang=en-US }}</ref> Transplantation of limbal stem cells is a promising therapy for limbal stem cell deficiency.<ref>{{cite journal |last1=Utheim |first1=O.A. |last2=Pasovic |first2=L. |last3=Raeder |first3=S. |last4=Eidet |first4=J.R. |last5=Fostad |first5=I.–G. |last6=Sehic |first6=A. |last7=Roald |first7=B. |last8=de la Paz |first8=M.F. |last9=Lyberg |first9=T. |last10=Dartt |first10=D. A. |last11=Utheim |first11=T.P. |date=2019-03-12 |title=Effects of explant size on epithelial outgrowth, thickness, stratification, ultrastructure, and phenotype of cultured limbal epithelial cells |journal=PLoS One |volume=14 |issue=3 |article-number=e0212524 |doi=10.1371/journal.pone.0212524 |doi-access=free |issn=1932-6203 |pmc=6413940 |pmid=30861002 |bibcode=2019PLoSO..1412524U |lang=en }}</ref>
==See also== * Circle contact lens * Corneal limbus * Limbus sign
==References== {{reflist|25em}}
==External links== * {{Commons category inline|Limbal rings}}
Category:Eye color
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