Editing Retinopathy (section)

==Pathophysiology==
The development of retinopathy can be broken down into proliferative and non-proliferative types. Both types cause disease by altering the normal blood flow to the retina through different mechanisms. The retina is supplied by small vessel branches from the [[central retinal artery]].<ref name=":1">{{Cite book|title=Pathophysiology : concepts of altered health states| veditors = Porth C, Matfin G |date=2009-01-01|publisher=Wolters Kluwer Health/Lippincott Williams & Wilkins|isbn=9780781766166|pages=756|oclc=181600926}}</ref> Proliferative retinopathy refers to damage caused by abnormal blood vessel growth.<ref>{{Cite web|url=http://accessmedicine.mhmedical.com/content.aspx?sectionid=40229327&bookid=387&Resultclick=2|title=Chapter 10. Retina {{!}} Vaughan & Asbury's General Ophthalmology, 18e {{!}} AccessMedicine {{!}} McGraw-Hill Medical|website=accessmedicine.mhmedical.com|language=en|access-date=2017-03-03}}</ref> Normally, [[angiogenesis]] is a natural part of tissue growth and formation. When there is an unusually high or fast rate of angiogenesis, there is an overgrowth of blood vessels called [[neovascularization]]. In the non-proliferative type, abnormal blood flow to the retina occurs due to direct damage or compromise of the blood vessels themselves. Many causes of retinopathy may cause both proliferative and non-proliferative types, though some causes are more associated one type.

=== Non-proliferative retinopathy ===
Non-proliferative retinopathy is often caused by direct damage or remodeling of the small blood vessels supplying the retina.<ref name=":1" /> Many common causes of non-proliferative damage include [[hypertensive retinopathy]], [[retinopathy of prematurity]], [[radiation retinopathy]], [[solar retinopathy]], [[sickle cell retinopathy]], and anemic retinopathy<ref>{{cite journal | vauthors = Carraro MC, Rossetti L, Gerli GC | title = Prevalence of retinopathy in patients with anemia or thrombocytopenia | journal = European Journal of Haematology | volume = 67 | issue = 4 | pages = 238–244 | date = October 2001 | pmid = 11860445 | doi = 10.1034/j.1600-0609.2001.00539.x | s2cid = 20875243 }}</ref> (including secondary to [[pernicious anemia|vitamin B12 deficiency]]<ref>{{cite journal | vauthors = Jojo V, Singh P | title = The eye: A lifesaver! An unusual case of Anemic Retinopathy secondary to Malnutrition and its recovery | journal = Journal of Family Medicine and Primary Care | volume = 9 | issue = 8 | pages = 4421–4424 | date = August 2020 | pmid = 33110874 | pmc = 7586514 | doi = 10.4103/jfmpc.jfmpc_577_20 | doi-access = free }}</ref>).

There are three main mechanisms of damage in non-proliferative retinopathy: blood vessel damage or remodeling, direct retinal damage, or occlusion of the blood vessels. The first mechanism is indirect damage by altering the blood vessels that supply the retina. In the case of [[hypertension]], high pressures in the system cause the walls of the artery to thicken, which effectively reduces the amount of blood flow to the retina.<ref name=":1" /> This reduction in flow causes tissue [[ischemia]] leading to damage. [[Atherosclerosis]], or hardening and narrowing of blood vessels, also reduces flow to the retina. The second mechanism is direct damage to the retina usually caused by [[free radicals]] that causes [[Oxidative stress|oxidative damage]] to the retina itself.<ref>Youseff PN, Sheibani N, Albert DM. Retinal light toxicity. Eye (Lond). 2011; 25(1):1–14.</ref> Radiation, solar retinopathy, and retinopathy of prematurity fall under this category. The third common mechanism is occlusion of blood flow. This can be caused by either physically blocking the vessels of the retinal artery branches or causing the arteries to narrow.<ref name=":2" /> Again, the result is reduced blood flow to the retina causing tissue damage. Sickle cell disease compromises blood flow by causing blood to sludge, or thicken and flow slowly, through the retinal arteries. Other disorders that cause [[hyperviscosity syndrome]] may also cause blood sludging. Lastly, clots or [[Retinal artery occlusion|central artery thrombosis]] directly blocks flow to the retina causing the cells to die.

=== Proliferative retinopathy ===
[[File:Fundus Proliferative retinopathy EDA01.JPG|thumb|Proliferative retinopathy during exam]]

Proliferative retinopathy is the result of aberrant blood flow to the retina due to blood vessel overgrowth, or neovascularization. These pathologically overgrown blood vessels are often fragile, weak, and ineffective at perfusing the retinal tissues.<ref>{{Cite web|url=http://accessmedicine.mhmedical.com/content.aspx?sectionid=79725409&bookid=1130&jumpsectionID=98704926&Resultclick=2|title=Use of the Hand-Held Ophthalmoscope {{!}} Harrison's Principles of Internal Medicine, 19e {{!}} AccessMedicine {{!}} McGraw-Hill Medical|website=accessmedicine.mhmedical.com|language=en|access-date=2017-03-06}}</ref> These weak, fragile vessels are also often leaky, allowing fluids, protein, and other debris to leach out into the retina. They are also prone to [[Bleeding|hemorrhage]] due to their poor strength. This makes proliferative types of retinopathy more risky since vessel hemorrhaging often leads to vision loss and blindness.<ref>{{Cite web|url=http://accessmedicine.mhmedical.com/content.aspx?sectionid=40279783&bookid=376&jumpsectionID=40289043&Resultclick=2|title=Chapter 52. Atherothrombosis: Disease Burden, Activity, and Vulnerability {{!}} Hurst's The Heart, 13e {{!}} AccessMedicine {{!}} McGraw-Hill Medical|website=accessmedicine.mhmedical.com|language=en|access-date=2017-03-06}}</ref> Many of the causes mentioned in non-proliferative retinopathy may also cause proliferative retinopathy at later stages. Angiogenesis and neovascularization tend to be a later manifestation of non-proliferative retinopathy. Many types of non-proliferative retinopathies result in tissue ischemia or direct retinal damage. The body responds by trying to increase blood flow to damaged retinal tissues.<ref>{{Cite web|url=http://accessmedicine.mhmedical.com/content.aspx?sectionid=40229327&bookid=387&jumpsectionID=40231861&Resultclick=2|title=Chapter 10. Retina {{!}} Vaughan & Asbury's General Ophthalmology, 18e {{!}} AccessMedicine {{!}} McGraw-Hill Medical|website=accessmedicine.mhmedical.com|language=en|access-date=2017-03-07}}</ref> [[Diabetes mellitus]], which causes [[diabetic retinopathy]], is the most common cause of proliferative retinopathy in the world.<ref>{{Cite web|url=https://nei.nih.gov/eyedata/diabetic|title=Diabetic Retinopathy {{!}} National Eye Institute|website=nei.nih.gov|language=en|access-date=2017-03-07}}</ref>

=== Other causes ===
Genetic mutations are rare causes of certain retinopathies and are usually [[X-linked]] including ''NDP'' family of genes causing [[Norrie disease]], [[Familial exudative vitreoretinopathy|FEVR]], and [[Coats' disease|Coats disease]] among others. There is emerging evidence that there may be a genetic predisposition in patients who develop retinopathy of prematurity and diabetic retinopathy.<ref>{{cite journal | vauthors = Hartnett ME, Cotten CM | title = Genomics in the neonatal nursery: Focus on ROP | journal = Seminars in Perinatology | volume = 39 | issue = 8 | pages = 604–610 | date = December 2015 | pmid = 26477493 | pmc = 4644692 | doi = 10.1053/j.semperi.2015.09.007 }}</ref><ref>{{cite journal | vauthors = Zhang Y, Xia W, Lu P, Yuan H | title = The Association between VDR Gene Polymorphisms and Diabetic Retinopathy Susceptibility: A Systematic Review and Meta-Analysis | journal = BioMed Research International | volume = 2016 | pages = 5305282 | date = 2016-11-06 | pmid = 27891515 | pmc = 5116338 | doi = 10.1155/2016/5305282 | doi-access = free }}</ref> Trauma, especially to the head, and several diseases may cause [[Purtscher's retinopathy]]. Physical exertion like weight lifting and aerobic exercise, coughing, sneezing, straining at stool, vomiting, sexual intercourse, blowing up balloons, blowing musical instruments, cardiopulmonary resuscitation or compression injuries may cause [[valsalva retinopathy]].<ref name="AAO">{{Cite web |title=Valsalva Retinopathy - EyeWiki |url=https://eyewiki.aao.org/Valsalva_Retinopathy#:~:text=Valsalva%20retinopathy%20is%20a%20preretinal,healthy%20eye%20and%20spontaneously%20resolves. |access-date=2022-04-24 |website=eyewiki.aao.org |language=en}}</ref>