Title: Collie eye anomaly

{{Short description|Congenital eye disease of dogs}}
'''Collie eye anomaly''' ('''CEA''') is a [[congenital]], [[heredity|inherited]], bilateral [[eye]] [[List of dog diseases|disease]] of [[dog]]s, which affects the [[retina]], [[choroid]], and [[sclera]].  It can be a mild disease or cause blindness.  CEA is caused by a simple [[autosome|autosomal]] [[recessive gene]] defect.  There is no treatment.

==Affected breeds==
It is known to occur in [[Collie]]s ([[Smooth Collie|smooth]] and [[Rough Collie|rough collies]]), [[Shetland Sheepdog]]s, [[Australian Shepherd]]s, [[Border Collie]]s,&lt;ref&gt;{{cite journal |url=https://www.cell.com/cell-reports/pdf/S2211-1247(17)30456-4.pdf |title=Genomic Analyses Reveal the Influence of Geographic Origin, Migration, and Hybridization on Modern Dog Breed Development |last1=Parker |first1=Heidi G. |display-authors=etal |date=25 April 2017 |journal=[[Cell Reports]] |language=en-US |volume=19 |issue=4 |publisher=[[Cell Press]] |pages=697–708 |doi=10.1016/j.celrep.2017.03.079 |doi-access=free |access-date=14 February 2025}}&lt;/ref&gt; [[Lancashire Heeler]]s,&lt;ref&gt;{{cite web | title = Inherited Retinopathies | work = The Merck Veterinary Manual | year = 2006 | url = http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/30114.htm | accessdate = 2007-03-19 }}&lt;/ref&gt; [[Nova Scotia Duck Tolling Retriever]]s,&lt;ref name=NSDTR_USA&gt;{{cite web|title=Nova Scotia Duck Tolling Retriever Club (USA) |work=Collie Eye Anomaly Discovered In The Nova Scotia Duck Tolling Retriever |url=http://www.nsdtrc-usa.org/CEAIntro.htm |accessdate=2006-05-26 |url-status=dead |archiveurl=https://web.archive.org/web/20070927064241/http://www.nsdtrc-usa.org/CEAIntro.htm |archivedate=September 27, 2007 }}&lt;/ref&gt; and the [[Hokkaido (dog breed)|Hokkaido]].&lt;ref&gt;{{cite journal | doi = 10.1136/vr.102015 | pmid=24939474 | title=Investigation of parallel and simultaneous selection for collie eye anomaly and ivermectin toxicosis | journal=Veterinary Record | date=2014 | volume=175 | issue=7 | pages=174 | first=K. | last=Mizukami| s2cid=37801535 }}&lt;/ref&gt;&lt;ref&gt;{{cite journal | doi = 10.1111/j.1463-5224.2011.00950.x | pmid=22051190 | title=Collie eye anomaly in Hokkaido dogs: case study | journal=Veterinary Ophthalmology | date=2011 | volume=15 | issue=2 | pages=128–132 | first=Keijiro | last=Mizukami}}&lt;/ref&gt; Frequency is high in Collies and Shetland Sheepdogs, and low in Border Collies&lt;ref name=Gelatt_1999&gt;{{cite book|editor=Gelatt, Kirk N.|title=Veterinary Ophthalmology|edition=3rd|publisher=Lippincott, Williams &amp; Wilkins|year=1999|isbn=0-683-30076-8}}&lt;/ref&gt; and NSDTRs.&lt;ref name=NSDTR_USA/&gt;  In the [[United States]], [[incidence (epidemiology)|incidence]] in the [[genotype]] of collies has been estimated to be as high as 95 percent, with a [[phenotype|phenotypic]] incidence of 80 to 85 percent.&lt;ref&gt;{{cite web|last=Gilger |first=Brian C. |title=Diagnosis and treatment of ocular fundus disorders of geriatric dogs |work=Proceedings of the North American Veterinary Conference |year=2006 |url=http://www.ivis.org/proceedings/navc/2006/SAE/305.pdf?LA=1 |format=PDF |accessdate=2007-03-19 |url-status=dead |archiveurl=https://web.archive.org/web/20070929110028/http://www.ivis.org/proceedings/navc/2006/SAE/305.pdf?LA=1 |archivedate=2007-09-29 }}&lt;/ref&gt;

==Pathogenesis==
CEA is caused by improper development of the eye.  Failure of the cells of the posterior portion of the [[optic vesicles]] to express [[growth hormone]] affects the [[Cellular differentiation|differentiation]] of other cells of the eye.  The choroid, especially lateral to the [[optic disc]], is [[hypoplasia|hypoplastic]] (underdeveloped).  A [[coloboma]], or hole, may form in or near the optic disc due to a failed closure of [[embryo]]nic tissue.  The degree of these abnormalities varies between individual dogs, and even between the same dog's eyes.&lt;ref&gt;{{cite web | last = Bedford | first = Peter | title = Hereditary Retinal Diseases | work = Proceedings of the 31st World Congress of the World Small Animal Veterinary Association | year = 2006 | url = http://www.ivis.org/proceedings/wsava/2006/lecture21/Bedford2.pdf?LA=1| format = PDF | accessdate = 2007-03-19 }}&lt;/ref&gt;  CEA is inherited as an autosomal recessive trait that has a [[penetrance]] reaching 100 percent.&lt;ref&gt;{{cite journal |vauthors=Lowe J, Kukekova A, Kirkness E, Langlois M, Aguirre G, Acland G, Ostrander E |title=Linkage mapping of the primary disease locus for collie eye anomaly |journal=Genomics |volume=82 |issue=1 |pages=86–95 |year=2003 |pmid=12809679 |doi=10.1016/S0888-7543(03)00078-8}}&lt;/ref&gt; A mutation in the [[NHEJ1]] gene is responsible.&lt;ref&gt;{{cite book |author1-first=James A.C. |author1-last=Oliver |author2-first=Cathryn S. |author2-last=Mellersh | editor1-first=Barbara | editor1-last=Cooper | editor2-first=Elizabeth |editor2-last=Mullineaux |editor3-first=Lynn | editor3-last=Turner |title=BSAVA Textbook of Veterinary Nursing |date=2020 |publisher=British Small Animal Veterinary Association |isbn=978-1-910-44339-2 |edition=Sixth|chapter=Genetics| page=131}}&lt;/ref&gt;

==Signs==
The most common sign of CEA is the presence of an area of undeveloped choroid (appearing as a pale spot) lateral to the optic disc.  The choroid is a collection of blood vessels supplying the retina.  CEA can also cause retinal or scleral coloboma, coloboma of the optic disc, [[retinal detachment]], or intraocular hemorrhage.  It can be diagnosed by [[ophthalmoscope|fundoscopy]] by the age of six or seven weeks.&lt;ref name=Gelatt_1999/&gt;  Severe cases may be blind.

==Breeding and testing==
Controversies exist around eliminating this disorder from breeding Collies.  Some [[veterinarian]]s advocate only breeding dogs with no evidence of disease, but this would eliminate a large portion of potential breeding stock.  Because of this, others recommend only breeding mildly affected dogs, but this would never completely eradicate the condition.  Also, mild cases of choroidal hypoplasia may become pigmented and therefore undiagnosable by the age of three to seven months.  If puppies are not checked for CEA before this happens, they may be mistaken for normal and bred as such.  Checking for CEA by seven weeks of age can eliminate this possibility.  Diagnosis is also difficult in dogs with [[coat (dog)|coat]]s of dilute color because lack of pigment in the choroid of these animals can be confused with choroidal hypoplasia.  Also, because of the lack of choroidal pigment, mild choroidal hypoplasia is difficult to see, and therefore cases of CEA may be missed.&lt;ref name=Gelatt_1999/&gt;

Until recently, the only way to know if a dog was a [[Asymptomatic carrier|carrier]] was for it to produce an affected puppy. However, a genetic test for CEA became available at the beginning of 2005, developed by the Baker Institute for Animal Health, [[Cornell University]], and administered through [http://www.optigen.com/ OptiGen].&lt;ref name=ABCA&gt;{{cite web | title=American Border Collie Association | work=Health and Genetics of Border Collies - A Breeder and Buyer's Guide | url=http://www.americanbordercollie.org/Health%20and%20Genetics%20of%20Border%20Collies.htm | accessdate=2006-07-28 | url-status=dead | archiveurl=https://web.archive.org/web/20060715013046/http://www.americanbordercollie.org/Health%20and%20Genetics%20of%20Border%20Collies.htm | archivedate=2006-07-15 }}&lt;/ref&gt; The test can determine whether a dog is affected, a carrier, or clear, and is therefore a useful tool in determining a particular dog's suitability for breeding.

==References==
{{Reflist}}

==External links==
*[http://www.collieeye.org.uk/ Informational website for CEA]
*[https://web.archive.org/web/20070505235217/http://www.optigen.com/opt9_test_cea_ch.html Optigen: Collie Eye Anomaly / Choroidal Hypoplasia (CEA) Test]

[[Category:Dog diseases]]