View source for Cataract

{{Short description|Clouding of the lens inside the eye, causing poor vision}}
{{Other uses}}
{{cs1 config|name-list-style=vanc|display-authors=6}}
{{Infobox medical condition
| name            = Cataract
| image           = Cataract in human eye.png
| caption         = Magnified view of a cataract seen on [[eye examination|examination]] with a [[slit lamp]]
| field           = [[Ophthalmology]], [[Optometry]]
| symptoms        = Faded colors, blurry vision, halos around light, trouble with bright lights, trouble seeing at night<ref name=NIH2009/>
| complications   = [[Falling (accident)|Falling]], [[Depression (mood)|depression]], [[blindness]]<ref name=Gim2011/><ref name=WHO2014/>
| onset           = Gradual<ref name=NIH2009/>
| duration        =
| causes          = [[senescence|Aging]], [[Trauma (medicine)|trauma]], [[radiation exposure]], following eye surgery, genetic<ref name=NIH2009/><ref name=WHOPri/><ref>{{cite journal | vauthors = Chan WH, Biswas S, Ashworth JL, Lloyd IC | title = Congenital and infantile cataract: aetiology and management | journal = European Journal of Pediatrics | volume = 171 | issue = 4 | pages = 625–630 | date = April 2012 | pmid = 22383071 | doi = 10.1007/s00431-012-1700-1 | s2cid = 195680440 }}</ref>
| risks           = [[diabetes mellitus|Diabetes]], [[smoking tobacco]], prolonged exposure to [[sunlight]], alcohol<ref name=NIH2009/>
| diagnosis       = [[Eye examination]]<ref name=NIH2009/>
| differential    =
| prevention      = [[Sunglasses]], proper diet, not smoking<ref name=NIH2009/>
| treatment       = [[Glasses]], [[cataract surgery]]<ref name=NIH2009/>
| medication      =
| prognosis       =
| frequency       = 60 million (2015)<ref name=GBD2015Pre>{{cite journal | title = Global, regional, and national incidence, prevalence, and years lived with disability for 310 diseases and injuries, 1990-2015: a systematic analysis for the Global Burden of Disease Study 2015 | journal = Lancet | volume = 388 | issue = 10053 | pages = 1545–1602 | date = October 2016 | pmid = 27733282 | pmc = 5055577 | doi = 10.1016/S0140-6736(16)31678-6 | last1 = Vos | first1 = Theo | last2 = Allen | first2 = Christine | last3 = Arora | first3 = Megha | last4 = Barber | first4 = Ryan M. | last5 = Bhutta | first5 = Zulfiqar A. | last6 = Brown | first6 = Alexandria | last7 = Carter | first7 = Austin | last8 = Casey | first8 = Daniel C. | last9 = Charlson | first9 = Fiona J. | last10 = Chen | first10 = Alan Z. | last11 = Coggeshall | first11 = Megan | last12 = Cornaby | first12 = Leslie | last13 = Dandona | first13 = Lalit | last14 = Dicker | first14 = Daniel J. | last15 = Dilegge | first15 = Tina | last16 = Erskine | first16 = Holly E. | last17 = Ferrari | first17 = Alize J. | last18 = Fitzmaurice | first18 = Christina | last19 = Fleming | first19 = Tom | last20 = Forouzanfar | first20 = Mohammad H. | last21 = Fullman | first21 = Nancy | last22 = Gething | first22 = Peter W. | last23 = Goldberg | first23 = Ellen M. | last24 = Graetz | first24 = Nicholas | last25 = Haagsma | first25 = Juanita A. | last26 = Hay | first26 = Simon I. | last27 = Johnson | first27 = Catherine O. | last28 = Kassebaum | first28 = Nicholas J. | last29 = Kawashima | first29 = Toana | last30 = Kemmer | first30 = Laura }}</ref>
| deaths          =
}}

<!-- Definition and symptoms -->
A '''cataract''' is a cloudy area in the [[lens (anatomy)|lens]] of the [[eye]] that leads to a [[visual impairment|decrease in vision]] of the eye.<ref name="NIH2009" /><ref name=":0" /> Cataracts often develop slowly and can affect one or both eyes.<ref name="NIH2009" /> Symptoms may include faded colours, blurry or [[double vision]], halos around light, trouble with bright lights, and [[Nyctalopia|difficulty seeing at night]].<ref name="NIH2009">{{cite web |date=September 2009 |title=Facts About Cataract |url=https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/cataracts |url-status=live |archive-url=https://web.archive.org/web/20150524095805/https://www.nei.nih.gov/health/cataract/cataract_facts |archive-date=24 May 2015 |access-date=24 May 2015}}</ref> This may result in trouble driving, reading and recognizing faces.<ref name="Allen-2006">{{cite journal | vauthors = Allen D, Vasavada A | title = Cataract and surgery for cataract | journal = BMJ | volume = 333 | issue = 7559 | pages = 128–132 | date = July 2006 | pmid = 16840470 | pmc = 1502210 | doi = 10.1136/bmj.333.7559.128 }}</ref> Poor vision caused by cataracts may also result in an increased risk of [[Falling (accident)|falling]] and [[Depression (mood)|depression]].<ref name="Gim2011">{{cite journal | vauthors = Gimbel HV, Dardzhikova AA | title = Consequences of waiting for cataract surgery | journal = Current Opinion in Ophthalmology | volume = 22 | issue = 1 | pages = 28–30 | date = January 2011 | pmid = 21076306 | doi = 10.1097/icu.0b013e328341425d | s2cid = 205670956 }}</ref> In 2020 Cataracts caused 39.6% of all cases of [[blindness]] and 28.3% of [[visual impairment]] worldwide. Cataracts remain the single most common cause of global blindness.<ref name="WHO2014">{{Cite journal |last=Pesudovs |first=Konrad |last2=Lansingh |first2=Van Charles |last3=Kempen |first3=John H. |last4=Tapply |first4=Ian |last5=Fernandes |first5=Arthur G. |last6=Cicinelli |first6=Maria Vittoria |last7=Arrigo |first7=Alessandro |last8=Leveziel |first8=Nicolas |last9=Resnikoff |first9=Serge |last10=Taylor |first10=Hugh R. |last11=Sedighi |first11=Tabassom |last12=Flaxman |first12=Seth |last13=Bikbov |first13=Mukkharram M. |last14=Braithwaite |first14=Tasanee |last15=Bron |first15=Alain |date=August 2024 |title=Global estimates on the number of people blind or visually impaired by cataract: a meta-analysis from 2000 to 2020 |url=https://www.nature.com/articles/s41433-024-02961-1 |journal=Eye |language=en |volume=38 |issue=11 |pages=2156–2172 |doi=10.1038/s41433-024-02961-1 |issn=1476-5454 |pmc=11269584 |pmid=38461217}}</ref>

<!-- Cause, mechanisms and diagnosis -->
Cataracts are most commonly due to [[senescence|aging]] but may also be due to [[Trauma (medicine)|trauma]] or radiation exposure, be [[congenital cataract|present from birth]] or occur following eye surgery for other problems.<ref name=NIH2009/><ref name=WHOPri>{{cite web|title=Priority eye diseases|url=https://www.who.int/blindness/causes/priority/en/index1.html|access-date=24 May 2015|archive-url=https://web.archive.org/web/20150524095804/http://www.who.int/blindness/causes/priority/en/index1.html|archive-date=24 May 2015}}</ref> Risk factors include [[diabetes mellitus|diabetes]], longstanding use of [[corticosteroid]] medication, [[smoking tobacco]], prolonged exposure to [[sunlight]] and [[Alcohol (drug)|alcohol]].<ref name=NIH2009/> In addition, poor nutrition, obesity, chronic kidney disease and autoimmune diseases have been recognized in various studies as contributing to the development of cataracts.<ref>{{Cite journal |last1=Ang |first1=Michael J. |last2=Afshari |first2=Natalie A. |date=2021 |title=Cataract and systemic disease: A review |url=https://onlinelibrary.wiley.com/doi/10.1111/ceo.13892 |journal=Clinical & Experimental Ophthalmology |language=en |volume=49 |issue=2 |pages=118–127 |doi=10.1111/ceo.13892 |pmid=33426783 |issn=1442-9071|url-access=subscription }}</ref> Cataract formation is primarily driven by oxidative stress, which damages lens proteins, leading to their aggregation and the accumulation of clumps of protein or yellow-brown pigment in the lens. This reduces the transmission of light to the retina at the back of the eye, impairing vision. Additionally, alterations in the lens's metabolic processes, including imbalances in calcium and other ions, contribute to cataract development.<ref>{{Cite journal |last=Spector |first=Abraham |date=1995 |title=Oxidative stress-induced cataract: mechanism of action |journal=The FASEB Journal |language=en |volume=9 |issue=12 |pages=1173–1182 |doi=10.1096/fasebj.9.12.7672510 |doi-access=free |pmid=7672510 |issn=1530-6860}}</ref><ref name=NIH2009/> Diagnosis is typically through an [[eye examination]],<ref name=NIH2009/> with ophthalmoscopy and slit-lamp examination being the most effective methods. During ophthalmoscopy the pupil is dilated and the red reflex is examined for any opacities in the lens. Slit-lamp examination provides further details on the characteristics, location and extent of the cataract.<ref>{{Cite web |title=Cataract - Eye Disorders |url=https://www.msdmanuals.com/professional/eye-disorders/cataract/cataract |access-date=2025-02-19 |website=MSD Manual Professional Edition |language=en}}</ref>

<!-- Prevention and treatment -->
Wearing [[sunglasses]] with UV protection and a wide brimmed hat, eating leafy vegetables and fruits and avoiding smoking may reduce the risk of developing cataracts or slow the process.<ref name=NIH2009/><ref name="NIH News in Health 2017 on cataract">{{cite web | title=Recognizing Cataracts | website=NIH News in Health | date=2017-05-30 | url=https://newsinhealth.nih.gov/2013/08/recognizing-cataracts | access-date=2020-02-02 | quote=Try wearing sunglasses or a hat with a brim. Researchers also believe that good nutrition can help reduce the risk of age-related cataract. They recommend eating plenty of green leafy vegetables, fruits, nuts and other healthy foods.}}</ref> Early on, the symptoms may be improved with [[glasses]].<ref name=NIH2009/> If this does not help, [[cataract surgery|surgery to remove the cloudy lens and replace it with an artificial lens]] is the only effective treatment.<ref name=NIH2009/> Cataract surgery is not readily available in many countries, and surgery is needed only if the cataracts are causing problems and generally results in an improved [[quality of life]].<ref name=NIH2009/><ref>{{cite journal | vauthors = Lamoureux EL, Fenwick E, Pesudovs K, Tan D | title = The impact of cataract surgery on quality of life | journal = Current Opinion in Ophthalmology | volume = 22 | issue = 1 | pages = 19–27 | date = January 2011 | pmid = 21088580 | doi = 10.1097/icu.0b013e3283414284 | s2cid = 22760161 }}</ref><ref name=WHOPri/><ref name=Rao2011/>

<!-- Epidemiology -->
About 20 million people worldwide are blind owing to cataracts.<ref name=WHOPri/> They are the cause of approximately 5% of blindness in the United States and nearly 60% of blindness in parts of Africa and South America.<ref name=Rao2011>{{cite journal | vauthors = Rao GN, Khanna R, Payal A | title = The global burden of cataract | journal = Current Opinion in Ophthalmology | volume = 22 | issue = 1 | pages = 4–9 | date = January 2011 | pmid = 21107260 | doi = 10.1097/icu.0b013e3283414fc8 | s2cid = 205670997 }}</ref> Blindness from cataracts occurs in 10 to 40 per 100,000 children in the [[Developing country|developing world]] and 1 to 4 per 100,000 children in the [[developed world]].<ref name=":0">{{cite book |last1=Wilson Jr. |first1=M. Edward |url=https://books.google.com/books?id=gLJZDD2igCMC&pg=PA20 |title=Pediatric cataract surgery techniques, complications, and management |last2=Trivedi |first2=Rupal H. |last3=Pandey |first3=Suresh K. |date=2005 |publisher=Lippincott Williams & Wilkins |isbn=978-0-7817-4307-5 |location=Philadelphia, Pennsylvania |page=20 |language=en |archive-url=https://web.archive.org/web/20150524134557/https://books.google.ca/books?id=gLJZDD2igCMC&pg=PA20 |archive-date=2015-05-24 |url-status=live}}</ref> Cataracts become more common [[Ageing|with age]].<ref name=NIH2009/> In the United States, cataracts occur in 68% of those over the age of 80 years.<ref name = NEI2019>{{Cite web|url=https://www.nei.nih.gov./learn-about-eye-health/eye-health-data-and-statistics|title=Cataract Data and Statistics |publisher=National Eye Institute|access-date=2019-11-18}}</ref> They are more common in women and less common in Hispanic and Black people.<ref name = NEI2019/>

== Signs and symptoms ==
{{multiple image
| caption_align     = center
| header_align      = center
| width             = 220
| image1            = Grauerstar-1.jpg
| alt1              = normal vision
| image2            = Grauerstar-2.jpg
| alt2              = vision with cataract
| footer            = An example of normal vision versus vision with cataracts
}}
[[File:Cataracts due to Congenital Rubella Syndrome (CRS) PHIL 4284 lores.jpg|thumb|Bilateral cataracts in an infant due to [[congenital rubella syndrome]] ]]
Signs and symptoms vary depending on the type of cataract, though considerable overlap occurs. People with [[#Classification|nuclear sclerotic]] or [[#Classification|brunescent]] cataracts often notice a [[Vision loss|reduction of vision]]. Nuclear cataracts typically cause greater impairment of distance vision than of near vision. Those with posterior subcapsular cataracts usually complain of [[Glare (vision)|glare]] as their major symptom.<ref>{{cite web|title=Posterior Supcapsular Cataract|work=Digital Reference of Ophthalmology|url=http://dro.hs.columbia.edu/lc1.htm|publisher=Edward S. Harkness Eye Institute, Department of Ophthalmology of Columbia University|year=2003|access-date=2 April 2013|url-status=live|archive-url=https://web.archive.org/web/20130327142432/http://dro.hs.columbia.edu/lc1.htm|archive-date=27 March 2013}}</ref>

The severity of cataract formation, assuming no other ocular disease is present, is primarily assessed using a visual acuity test. Additional symptoms may include frequent changes in glasses prescription and the appearance of colored halos around lights, which can be attributed to the hydration of the lens.<ref name="nei">{{cite web |title=Cataracts |url=https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/cataracts |publisher=National Eye Institute, US National Institutes of Health |access-date=5 March 2025 |date=10 December 2024}}</ref>

[[Congenital cataract]]s can result in [[amblyopia]] if not treated in a timely manner.<ref name="ambly">{{cite web |title=Amblyopia (Lazy eye) |url=https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/amblyopia-lazy-eye |publisher=National Eye Institute, US National Institutes of Health |access-date=5 March 2025 |date=26 November 2024}}</ref><ref name=Moh2019>{{cite journal | vauthors = Mohammadpour M, Shaabani A, Sahraian A, Momenaei B, Tayebi F, Bayat R, Mirshahi R | title = Updates on managements of pediatric cataract | journal = Journal of Current Ophthalmology | volume = 31 | issue = 2 | pages = 118–126 | date = June 2019 | pmid = 31317088 | pmc = 6611931 | doi = 10.1016/j.joco.2018.11.005 | doi-access = free }}</ref>

== Causes ==

===Age===
Age is the most common cause of cataracts.<ref name=NIH2009/><ref name=WHOPri/> Lens proteins [[Denaturation (biochemistry)|denature]] and degrade over time, and this process is accelerated by diseases such as [[diabetes mellitus]] and [[hypertension]]. Environmental factors, including toxins, radiation, and [[ultraviolet light]] have cumulative effects which are worsened by the loss of protective and restorative mechanisms due to alterations in gene expression and chemical processes within the eye.<ref name="yanoff">{{cite book |title=Ophthalmology |vauthors=Duker JS, Yanoff M |publisher=Mosby/Elsevier |year=2009 |isbn=978-0-323-04332-8 |location=St. Louis, Missouri |language=en-us}}{{page needed|date=May 2016}}</ref>

[[Oxidative stress]] associated with [[lipid peroxidation]] is an important pathogenic mechanism in cataract formation.<ref name="Hsueh2022">{{cite journal | doi=10.3390/ijms23031255 | doi-access=free | title=The Pathomechanism, Antioxidant Biomarkers, and Treatment of Oxidative Stress-Related Eye Diseases | date=2022 | last1=Hsueh | first1=Yi-Jen | last2=Chen | first2=Yen-Ning | last3=Tsao | first3=Yu-Ting | last4=Cheng | first4=Chao-Min | last5=Wu | first5=Wei-Chi | last6=Chen | first6=Hung-Chi | journal=International Journal of Molecular Sciences | volume=23 | issue=3 | page=1255 | pmid=35163178 | pmc=8835903 }}</ref><ref>{{Cite journal|title=Lipid peroxidation: pathophysiological and pharmacological implications in the eye|first1=Ya Fatou|last1=Njie-Mbye|first2=Madhura|last2=Chitnis|first3=Catherine|last3=Opere|first4=Sunny|last4=Ohia|date=January 18, 2013|journal=Frontiers in Physiology|volume=4|page=366 |doi=10.3389/fphys.2013.00366|doi-access=free |pmid=24379787 |pmc=3863722}}</ref> Senile cataracts are associated with a decrease in [[antioxidant]] capacity in the lens.<ref name = Hsueh2022/> An increase in oxidative stress in the lens or a decrease in the ability to remove [[reactive oxygen species]] can lead to the lens becoming more opaque.<ref name = Hsueh2022/>

===Trauma===
[[File:Rosette cataract.jpg|thumb|Post traumatic rosette cataract of a 60-year-old male]]
Blunt trauma causes swelling, thickening, and whitening of the lens fibers. While the swelling normally resolves with time, the white color may remain. In severe blunt trauma, or in injuries that penetrate the eye, the capsule in which the lens sits can be damaged. This damage allows fluid from other parts of the eye to rapidly enter the lens leading to swelling and then whitening, obstructing light from reaching the retina at the back of the eye. Cataracts may develop in 0.7 to 8.0% of cases following [[electrical injury|electrical injuries]].<ref>{{cite journal | vauthors = Reddy SC | title = Electric cataract: a case report and review of the literature | journal = European Journal of Ophthalmology | volume = 9 | issue = 2 | pages = 134–138 | year = 1999 | pmid = 10435427 | doi = 10.1177/112067219900900211 | s2cid = 45814684 }}</ref> Blunt trauma can also result in star- (stellate) or petal-shaped cataracts.<ref>{{cite journal | vauthors = Ram J, Gupta R | title = Images in Clinical Medicine. Petaloid Cataract | journal = The New England Journal of Medicine | volume = 374 | issue = 18 | pages = e22 | date = May 2016 | pmid = 27144871 | doi = 10.1056/NEJMicm1507349 }}</ref>

===Radiation===
Cataracts can arise as an effect of exposure to various types of radiation. X-rays, one form of [[Radiobiology|ionizing radiation]], may damage the DNA of lens cells.<ref name = "Lipman1988">{{cite journal | vauthors = Lipman RM, Tripathi BJ, Tripathi RC | title = Cataracts induced by microwave and ionizing radiation | journal = Survey of Ophthalmology | volume = 33 | issue = 3 | pages = 200–210 | year = 1988 | pmid = 3068822 | doi = 10.1016/0039-6257(88)90088-4 }}</ref> Ultraviolet light, specifically [[UVB]], has also been shown to cause cataracts, and some evidence indicates sunglasses worn at an early age can slow its development in later life.<ref>{{cite journal | vauthors = Sliney DH | title = UV radiation ocular exposure dosimetry | journal = Documenta Ophthalmologica. Advances in Ophthalmology | volume = 88 | issue = 3–4 | pages = 243–254 | year = 1994 | pmid = 7634993 | doi = 10.1007/bf01203678 | s2cid = 8242055 }}</ref> [[microwave#Effects on health|Microwave]]s, a type of [[nonionizing radiation]], may cause harm by denaturing protective enzymes (e.g., [[glutathione peroxidase]]), by oxidizing [[Cysteine|protein thiol]] groups (causing [[protein aggregation]]), or by damaging lens cells via thermoelastic expansion.<ref name = "Lipman1988" /> The protein coagulation caused by electric and heat injuries whitens the lens.<ref name="yanoff" /> This same process is what makes the clear albumen of an egg become white and opaque during cooking.{{citation needed|date=June 2022}}

===Genetics===
[[File:Chrismas tree cataract.jpg|thumb|Christmas tree cataract (diffuse illumination)]]
The genetic component is strong in the development of cataracts,<ref>{{citation |page=77 |chapter=Molecular Genetics of Cataract |title=Genetics in Ophthalmology |publisher=Karger Medical and Scientific Publishers |year=2003 |isbn=978-3-8055-7578-2 | vauthors = Hejtmancik JF, Smaoui N }}</ref> most commonly through mechanisms that protect and maintain the lens. The presence of cataracts in childhood or early life can occasionally be due to a particular syndrome. Examples of [[Chromosomal disorder|chromosome abnormalities]] associated with cataracts include [[1q21.1 deletion syndrome]], [[cri-du-chat syndrome]], [[Down syndrome]], [[Patau's syndrome]], [[trisomy 18]] ([[Edward's syndrome]]), and [[Turner's syndrome]], and in the case of [[neurofibromatosis type 2]], [[juvenile cataract]] on one or both sides may be noted. Examples of [[single-gene disorder]] include [[Alport's syndrome]], [[Conradi's syndrome]], [[cerebrotendineous xanthomatosis]], [[myotonic dystrophy]], and [[oculocerebrorenal syndrome]] or [[Lowe syndrome]].<ref>{{Cite journal |last1=Li |first1=Jinyu |last2=Xia |first2=Chun-hong |last3=Wang |first3=Eddie |last4=Yao |first4=Ke |last5=Gong |first5=Xiaohua |date=2017 |title=Screening, genetics, risk factors, and treatment of neonatal cataracts |journal=Birth Defects Research |language=en |volume=109 |issue=10 |pages=734–743 |doi=10.1002/bdr2.1050 |issn=2472-1727 |pmc=9211061 |pmid=28544770}}</ref>

===Skin diseases===
The skin and the lens have the same embryological origin and so can be affected by similar diseases.<ref>{{citation |page=507 |title=Ophthalmology | vauthors = Yanoff M, Duker JS |publisher=Elsevier Health Sciences |year=2009 |isbn=978-0-323-04332-8}}</ref> Those with [[atopic dermatitis]] and [[eczema]] occasionally develop shield ulcer cataracts.{{Citation needed|date=November 2024}} [[Ichthyosis]] is an autosomal recessive disorder associated with cuneiform cataracts and nuclear sclerosis. [[Nevoid basal-cell carcinoma syndrome|Basal-cell nevus]] and [[pemphigus]] have similar associations.{{citation needed|date=September 2022}}

===Smoking and alcohol===

[[Tobacco smoking|Cigarette smoking]] has been shown to increase the risk of age-related cataract and nuclear cataract.<ref>{{cite journal|year=2012|author=Ye J, He J, Wang C, Wu H, Shi X, Zhang H, Xie J, Lee SY.|title=Smoking and risk of age-related cataract: a meta-analysis|journal=Invest Ophthalmol Vis Sci|volume=53|issue=7|pages=3885–3895|doi=10.1167/iovs.12-9820|pmid=22599585}}</ref><ref>{{cite journal|year=2019|author=Beltrán-Zambrano E, García-Lozada D, Ibáñez-Pinilla E.|title= Risk of cataract in smokers: A meta-analysis of observational studies|journal=Arch Soc Esp Oftalmol (Engl Ed)|volume=94|issue=2|pages=60–74|doi=10.1016/j.oftal.2018.10.020|pmid=30528895|s2cid=155984835 }}</ref> Evidence is conflicting over the effect of alcohol. Some surveys have shown a link, but others that followed people over longer terms have not.<ref>{{cite journal | vauthors = Wang S, Wang JJ, Wong TY | title = Alcohol and eye diseases | journal = Survey of Ophthalmology | volume = 53 | issue = 5 | pages = 512–525 | year = 2008 | pmid = 18929762 | doi = 10.1016/j.survophthal.2008.06.003 }}</ref>

===Inadequate vitamin C===
Low [[vitamin C]] intake and serum levels have been associated with greater cataract rates.<ref name = "WeiLiang2016">{{cite journal | vauthors = Wei L, Liang G, Cai C, Lv J | title = Association of vitamin C with the risk of age-related cataract: a meta-analysis | journal = Acta Ophthalmologica | volume = 94 | issue = 3 | pages = e170–e176 | date = May 2016 | pmid = 25735187 | doi = 10.1111/aos.12688 | s2cid = 42785248 | doi-access = free }}</ref> However use of supplements of vitamin C has not demonstrated benefit.<ref name=Matthew2012/>

===Medications===
Some medications, such as systemic, topical, or inhaled [[corticosteroid]]s, may increase the risk of cataract development.<ref>{{cite journal | vauthors = Weatherall M, Clay J, James K, Perrin K, Shirtcliffe P, Beasley R | title = Dose-response relationship of inhaled corticosteroids and cataracts: a systematic review and meta-analysis | journal = Respirology | volume = 14 | issue = 7 | pages = 983–990 | date = September 2009 | pmid = 19740259 | doi = 10.1111/j.1440-1843.2009.01589.x | s2cid = 43843511 }}</ref><ref name=Hod1995/> Corticosteroids most commonly cause posterior subcapsular cataracts.<ref name=Hod1995>{{cite journal | vauthors = Hodge WG, Whitcher JP, Satariano W | title = Risk factors for age-related cataracts | journal = Epidemiologic Reviews | volume = 17 | issue = 2 | pages = 336–346 | date = 1995 | pmid = 8654515 | doi = 10.1093/oxfordjournals.epirev.a036197 }}</ref> People with [[schizophrenia]] often have risk factors for lens opacities (such as diabetes, hypertension, and poor nutrition). Second-generation [[antipsychotic]] medications are unlikely to contribute to cataract formation.<ref>{{cite journal | vauthors = Uçok A, Gaebel W | title = Side effects of atypical antipsychotics: a brief overview | journal = World Psychiatry | volume = 7 | issue = 1 | pages = 58–62 | date = February 2008 | pmid = 18458771 | pmc = 2327229 | doi = 10.1002/j.2051-5545.2008.tb00154.x }}</ref> [[Miotics]]<ref>{{cite journal | vauthors = van den Brûle J, Degueldre F, Galand A | title = [Drug-induced cataracts] | language = fr | journal = Revue Médicale de Liège | volume = 53 | issue = 12 | pages = 766–769 | date = December 1998 | pmid = 9927876 | trans-title = Drug-induced cataracts }}</ref> and [[triparanol]] may increase the risk.<ref>{{cite web |url=https://www.nlm.nih.gov/cgi/mesh/2012/MB_cgi?mode=&term=Triparanol&field=entry |title=Triperanol |publisher=National Library of Medicine |work=MeSH |access-date=2013-02-06 |archive-url=https://web.archive.org/web/20151222085138/http://www.nlm.nih.gov/cgi/mesh/2012/MB_cgi?mode=&term=Triparanol&field=entry |archive-date=2015-12-22 }}</ref>

===Post-operative===
Nearly every person who undergoes a [[vitrectomy]]—without ever having had cataract surgery—will experience progression of [[nuclear sclerosis]] after the operation.<ref>{{cite journal | vauthors = Almony A, Holekamp NM, Bai F, Shui YB, Beebe D | title = Small-gauge vitrectomy does not protect against nuclear sclerotic cataract | journal = Retina | volume = 32 | issue = 3 | pages = 499–505 | date = March 2012 | pmid = 22392091 | doi = 10.1097/IAE.0b013e31822529cf | s2cid = 31308270 }}</ref> This may be because the native vitreous humor is different from the solutions used to replace the vitreous (vitreous substitutes), such as [[Balanced salt solution#Surgical irrigation solutions|BSS Plus]].<ref>{{cite journal | vauthors = Kokavec J, Min SH, Tan MH, Gilhotra JS, Newland HS, Durkin SR, Grigg J, Casson RJ | title = Biochemical analysis of the living human vitreous | journal = Clinical & Experimental Ophthalmology | volume = 44 | issue = 7 | pages = 597–609 | date = September 2016 | pmid = 26891415 | doi = 10.1111/ceo.12732 | doi-access = free }}</ref> This may also be because the native vitreous humour contains [[ascorbic acid]] which helps neutralize oxidative damage to the lens and because conventional vitreous substitutes do not contain ascorbic acid.<ref>{{cite journal | vauthors = Donati S, Caprani SM, Airaghi G, Vinciguerra R, Bartalena L, Testa F, Mariotti C, Porta G, Simonelli F, Azzolini C | title = Vitreous substitutes: the present and the future | journal = BioMed Research International | volume = 2014 | article-number = 351804 | year = 2014 | pmid = 24877085 | pmc = 4024399 | doi = 10.1155/2014/351804 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Shui YB, Holekamp NM, Kramer BC, Crowley JR, Wilkins MA, Chu F, Malone PE, Mangers SJ, Hou JH, Siegfried CJ, Beebe DC | title = The gel state of the vitreous and ascorbate-dependent oxygen consumption: relationship to the etiology of nuclear cataracts | journal = Archives of Ophthalmology | volume = 127 | issue = 4 | pages = 475–482 | date = April 2009 | pmid = 19365028 | pmc = 2683478 | doi = 10.1001/archophthalmol.2008.621 }}</ref> Accordingly, for phakic patients requiring a vitrectomy it is becoming increasingly common for ophthalmologists to offer the vitrectomy combined with prophylactic [[cataract surgery]] to prevent cataract formation.<ref>{{cite journal | vauthors = Jalil A, Steeples L, Subramani S, Bindra MS, Dhawahir-Scala F, Patton N | title = Microincision cataract surgery combined with vitrectomy: a case series | journal = Eye | volume = 28 | issue = 4 | pages = 386–389 | date = April 2014 | pmid = 24406418 | pmc = 3983625 | doi = 10.1038/eye.2013.300 }}</ref>

===Hyperbaric oxygen therapy===

[[Hyperbaric oxygen therapy]] (HBOT) is the administration of 100% oxygen at pressures greater than one-atmosphere absolute pressure (1 ATA) for a therapeutic purpose. HBOT can have several side effects, including the long-term development of cataracts. This is rare and generally associated with multiple HBOT exposures over a long period. As it does not usually become symptomatic during HBOT, it may often go unrecognised and is probably under-reported. Evidence is emerging that lifetime dosage of oxygen may be a precipitating factor in the development of age-related cataracts. Nuclear cataracts have been hypothesized to be the end stage of the far better known phenomenon of [[Hyperoxic myopia|hyperbaric myopic shift]].<ref name="Bennett and Cooper 2022" >{{cite journal |url=https://www.ncbi.nlm.nih.gov/books/NBK470454/ |website=www.ncbi.nlm.nih.gov |publisher=StatPearls Publishing LLC. |title=Hyperbaric Cataracts |first1=Michael H.|last1=Bennett |first2=Jeffrey S. |last2=Cooper |date=10 August 2022 |pmid=29261974 |access-date=27 February 2023 }}</ref>

===Other diseases===
{{Col-begin}}
{{Col-break}}
* [[Metabolic disease|Metabolic]] and nutritional diseases{{citation needed|date=September 2022}}
** [[Aminoaciduria]] or [[Oculocerebrorenal syndrome|Lowe's syndrome]]
** [[Cerebrotendineous xanthomatosis]]
** [[Diabetes mellitus]]
** [[Fabry's disease]]
** [[Galactosemia]] / [[galactosemic cataract]]
** [[Homocystinuria]]
** [[Hyperparathyroidism]]
** [[Hypoparathyroidism]]
** [[Hypervitaminosis D]]
** [[Hypothyroidism]]
** [[Hypocalcaemia]]
** [[Mucopolysaccharidoses]]
** [[Wilson's disease]]
* [[congenital cataract|Congenital]]
** [[Congenital syphilis]]
** [[Cytomegalic inclusion disease]]
** [[Rubella]]
** [[Cockayne syndrome]]
{{Col-break}}
* Genetic syndromes
** [[Down syndrome]]
** [[Patau syndrome]]
** [[Edwards syndrome]]
* Infections:
** [[Cysticercosis]]
** [[Leprosy]]
** [[Onchocerciasis]]
** [[Toxoplasmosis]]
** [[Varicella]]
* Secondary to other eye diseases:
** [[Retinopathy of prematurity]]
** [[Aniridia]]
** [[Uveitis]]
** [[Retinal detachment]]
** [[Retinitis pigmentosa]]
{{Col-break}}
[[File:Sunflower cataract.jpg|thumb|Sunflower cataract of a forty-year-old male with Wilson's disease and decompensated chronic liver disease]]
{{col-end}}

==Diagnosis==
===Classification===
[[File:Human eye cross-sectional view grayscale.png|thumb|Cross-sectional view, showing the position of the human lens]]
[[File:Fetal cataract.ogv|thumb|Ultrasound scan of a unilateral cataract seen in a fetus at twenty weeks of pregnancy]]

Cataracts may be partial or complete, stationary or progressive, hard or soft. Histologically, the main types of age-related cataracts are nuclear sclerosis, cortical, and posterior subcapsular.<ref>{{Citation |last1=Aliancy |first1=Joah F. |title=Crystalline Lens and Cataract |date=1995 |work=Webvision: The Organization of the Retina and Visual System |editor-last=Kolb |editor-first=Helga |url=https://www.ncbi.nlm.nih.gov/books/NBK476171/ |access-date=2023-04-24 |place=Salt Lake City, Utah |publisher=University of Utah Health Sciences Center |pmid=29356473 |last2=Mamalis |first2=Nick |editor2-last=Fernandez |editor2-first=Eduardo |editor3-last=Nelson |editor3-first=Ralph}}</ref>

{{visible anchor|Nuclear sclerosis}} is the most common type of cataract, and involves the central or 'nuclear' part of the lens. This eventually becomes hard, or 'sclerotic', due to condensation on the lens nucleus and the deposition of brown pigment within the lens. In its advanced stages, it is called a brunescent cataract. In early stages, an increase in sclerosis may cause an increase in refractive index of the lens.<ref name=Bollinger_2008/> This causes a myopic shift (lenticular shift) that decreases hyperopia and enables presbyopic patients to see at near without reading glasses. This is only temporary and is called second sight.<ref name="Academic Press">{{Citation |last1=Joo |first1=C. -K. |title=Posterior Subcapsular and Anterior Polar Cataract |date=2010-01-01 |encyclopedia=Encyclopedia of the Eye |pages=476–479 |editor-last=Dartt |editor-first=Darlene A. |url=https://www.sciencedirect.com/science/article/pii/B9780123742032000403 |access-date=2024-02-20 |place=Oxford |publisher=Academic Press |doi=10.1016/b978-0-12-374203-2.00040-3 |isbn=978-0-12-374203-2 |last2=Choi |first2=J. -C. |last3=Kwan |first3=H. -G. |last4=Kim |first4=H.|url-access=subscription }}</ref>

{{visible anchor|Cortical cataracts}} are due to the lens cortex (outer layer) becoming opaque. They occur when changes in the fluid contained in the periphery of the lens cause fissuring.{{how|date=May 2024}}  When these cataracts are viewed through an [[ophthalmoscope]], or other magnification system, the appearance is similar to white spokes of a wheel. Symptoms often include problems with glare and light scatter at night.<ref name=Bollinger_2008>{{cite journal | vauthors = Bollinger KE, Langston RH | title = What can patients expect from cataract surgery? | journal = Cleveland Clinic Journal of Medicine | volume = 75 | issue = 3 | pages = 193–96, 199–200 | date = March 2008 | pmid = 18383928 | doi = 10.3949/ccjm.75.3.193| doi-broken-date = 1 July 2025 | s2cid = 27022598 }}</ref>

{{visible anchor|Posterior subcapsular cataracts}} are cloudy at the back of the lens adjacent to the capsule (or bag) in which the lens sits. Because light becomes more focused toward the back of the lens, they can cause disproportionate symptoms for their size.<ref name="Academic Press"/>

An immature cataract has some transparent protein, but with a mature cataract, all the lens protein is opaque. In a hypermature or Morgagnian cataract, the lens proteins have become liquid. Congenital cataract, which may be detected in adulthood, has a different classification and includes lamellar, polar, and sutural cataracts.<ref name=spencer>{{cite journal | vauthors = Spencer RW, Andelman SY | title = Steroid cataracts. Posterior subcapsular cataract formation in rheumatoid arthritis patients on long term steroid therapy | journal = Archives of Ophthalmology | volume = 74 | pages = 38–41 | date = July 1965 | pmid = 14303339 | doi = 10.1001/archopht.1965.00970040040009 }}</ref><ref>{{cite journal | vauthors = Greiner JV, Chylack LT | title = Posterior subcapsular cataracts: histopathologic study of steroid-associated cataracts | journal = Archives of Ophthalmology | volume = 97 | issue = 1 | pages = 135–144 | date = January 1979 | pmid = 758890 | doi = 10.1001/archopht.1979.01020010069017 }}</ref>

Cataracts can be classified by using the lens opacities classification system LOCS III. In this system, cataracts are classified based on type as nuclear, cortical, or posterior. The cataracts are further classified based on severity on a scale from 1 to 5. The LOCS III system is highly reproducible.<ref name="Yanoff_412">{{cite book |title=Ophthalmology |vauthors=Yanoff M, Duker JS |publisher=Mosby |year=2008 |isbn=978-0-323-05751-6 |edition=3rd |location=Edinburgh, Scotland |page=412 |language=en-uk}}</ref>

{{Gallery
|title=Different types of cataracts
|width=200
|height=200
|align=center
|File:Posterior polar cataract.jpg|alt1=ppc|Posterior polar cataract of an 8-year-old boy in left eye
|File:Nuclear sclerosis.jpg|alt2=ns |Nuclear sclerosis cataract of a 70-year-old male
|File:Cortical Cataract.jpg|alt3=cc|Cortical cataract of a 60-year-old male
|File:Cortical cataract.jpg|alt4=cc|Retroillumination of cortical cataract
|File:Posterior Subcapsular Cataract.jpg|alt5=psc|Posterior subcapsular cataract of a 16-year-old girl with type 1 diabetes
|File:Intumescent cataract.jpg|alt6=ic|Intumescent cataract of a 55-year-old male
|File:Anterior subcapsular cataract.jpg|alt7=asc|Anterior subcapsular cataract having back shadow
|File:Posterior subcapsular cataract.jpg|alt8=psc|Posterior subcapsular cataract by retroillumination
|File:Nuclear sclerosis and posterior polar cataract.jpg|alt9=ns & ppc|Nuclear sclerosis and posterior polar cataract of a 60-year-old female
|File:Dense white mature cataract.jpg|alt10=dc |Dense white mature cataract of a 60-year-old male
|File:Cataracte Corticale.png|alt11=dc |Cortical cataract of a melanoderm male
}}

==Prevention==
Risk factors such as UVB exposure and smoking can be addressed. Although no means of preventing cataracts has been scientifically proven, wearing [[sunglasses]] that block [[ultraviolet]] light may slow their development.<ref name=Neale2003>{{cite journal | vauthors = Neale RE, Purdie JL, Hirst LW, Green AC | title = Sun exposure as a risk factor for nuclear cataract | journal = Epidemiology | volume = 14 | issue = 6 | pages = 707–712 | date = November 2003 | pmid = 14569187 | doi = 10.1097/01.ede.0000086881.84657.98 | s2cid = 40041207 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Javitt JC, Wang F, West SK | title = Blindness due to cataract: epidemiology and prevention | journal = Annual Review of Public Health | volume = 17 | pages = 159–177 | year = 1996 | pmid = 8724222 | doi = 10.1146/annurev.pu.17.050196.001111 | doi-access = free }} Cited in ''Five-Year Agenda for the National Eye Health Education Program (NEHEP)'', p. B-2; National Eye Institute, U.S. National Institutes of Health</ref> While adequate intake of vitamins [[vitamin A|A]], [[vitamin C|C]], and [[vitamin E|E]] may protect against the risk of cataracts, [[clinical trial]]s have shown no benefit from supplements,<ref name="Matthew2012">{{cite journal | vauthors = Mathew MC, Ervin AM, Tao J, Davis RM | title = Antioxidant vitamin supplementation for preventing and slowing the progression of age-related cataract | journal = The Cochrane Database of Systematic Reviews | volume = 2012 | issue = 6 | article-number = CD004567 | date = June 2012 | pmid = 22696344 | pmc = 4410744 | doi = 10.1002/14651858.CD004567.pub2 }}</ref> although the evidence is mixed, but weakly positive, for a potential protective effect of the [[carotenoid]]s, [[lutein]] and [[zeaxanthin]].<ref>{{cite journal | vauthors = Barker FM | title = Dietary supplementation: effects on visual performance and occurrence of AMD and cataracts | journal = Current Medical Research and Opinion | volume = 26 | issue = 8 | pages = 2011–2023 | date = August 2010 | pmid = 20590393 | doi = 10.1185/03007995.2010.494549 | s2cid = 206965363 }}</ref><ref name="MaHao2013">{{cite journal | vauthors = Ma L, Hao ZX, Liu RR, Yu RB, Shi Q, Pan JP | title = A dose-response meta-analysis of dietary lutein and zeaxanthin intake in relation to risk of age-related cataract | journal = Graefe's Archive for Clinical and Experimental Ophthalmology = Albrecht von Graefes Archiv für Klinische und Experimentelle Ophthalmologie | volume = 252 | issue = 1 | pages = 63–70 | date = January 2014 | pmid = 24150707 | doi = 10.1007/s00417-013-2492-3 | s2cid = 13634941 }}</ref><ref name="Hayashi2015">{{cite book |title=Studies on the Cornea and Lens |vauthors=Hayashi R |date=2014-11-01 |isbn=978-1-4939-1934-5 |veditors=Babizhayev MA, Li DW, Kasus-Jacobi A, Žorić L, Alió JL |series=Oxidative Stress in Applied Basic Research and Clinical Practice |pages=317–326 |language=en |chapter=The Effects of Lutein in Preventing Cataract Progression |doi=10.1007/978-1-4939-1935-2_17}}</ref>

==Treatment==

===Surgical===

{{main|Cataract surgery}}
[[File:Cataract surgery.jpg|thumb|Cataract surgery, using a temporal-approach phacoemulsification probe (in right hand) and "chopper" (in left hand) being done under operating microscope at the U.S. Navy Medical Center in Portsmouth, Virginia]]
[[File:Posterior capsular opacification on retroillumination.jpg|thumb|[[Slit lamp]] photo of posterior capsular opacification visible a few months after implantation of intraocular lens, seen on retroillumination]]
The appropriateness of surgery depends on a person's particular functional and visual needs and other risk factors.<ref name=vaughan>{{cite book| vauthors = Cunningham ET, Riordan-Eva P |title=Vaughan & Asbury's general ophthalmology.|publisher=McGraw-Hill Medical|isbn=978-0-07-163420-5|edition=18th|year=2011}}{{page needed|date=May 2016}}</ref> Cataract removal can be performed at any stage and no longer requires ripening of the lens.{{clarify|what is ripening of the lens?|date=December 2023}} Surgery is usually [[Outpatient surgery|outpatient]] and usually performed using [[local anesthetic|local anesthesia]]. About 9 of 10 patients can achieve a corrected vision of 20/40 or better after surgery.<ref name=Bollinger_2008/>

Several recent evaluations found that cataract surgery can meet expectations only when significant functional impairment due to cataracts exists before surgery. Visual function estimates such as VF-14 have been found to give more realistic estimates than visual acuity testing alone.<ref name=Bollinger_2008/><ref name="Davis_2012">{{cite journal | vauthors = Davis JC, McNeill H, Wasdell M, Chunick S, Bryan S | title = Focussing both eyes on health outcomes: revisiting cataract surgery | journal = BMC Geriatrics | volume = 12 | article-number = 50 | date = September 2012 | pmid = 22943071 | pmc = 3497611 | doi = 10.1186/1471-2318-12-50 | doi-access = free }} {{open access}}</ref> In some developed countries, a trend to overuse cataract surgery has been noted, which may lead to disappointing results.<ref name=Black_2009>{{cite journal | vauthors = Black N, Browne J, van der Meulen J, Jamieson L, Copley L, Lewsey J | title = Is there overutilisation of cataract surgery in England? | journal = The British Journal of Ophthalmology | volume = 93 | issue = 1 | pages = 13–17 | date = January 2009 | pmid = 19098042 | doi = 10.1136/bjo.2007.136150 | s2cid = 37414146 | url = http://eprints.gla.ac.uk/5530/1/5530.pdf }}<!--http://eprints.gla.ac.uk/5530/1/5530.pdf--></ref>

[[Phacoemulsification]] is the most widely used cataract surgery in the developed world.<ref>{{citation |title=Studies on the Cornea and Lens |publisher=Springer |year=2014 |isbn=978-1-4939-1935-2 |page=4 | vauthors = Kim E, Yoon SY, Shin YJ }}</ref><ref>{{citation |title=Essential Principles of Phacoemulsification |vauthors=Pascal H |year=2013 |publisher=JP Medical Limited |isbn=978-9962-678-61-8}}{{page needed|date=May 2016}}.</ref> This procedure uses ultrasonic energy to emulsify the cataract lens. Phacoemulsification typically comprises six steps:<ref>{{citation|title=Pardianto G, Tassignon MJ. (eds) Innovation in Cataract Surgery |publisher=Springer Singapore |year=2024 |isbn=978-981-97-5191-4}}</ref>
* Anaesthetic – The eye is numbed with either a subtenon injection around the eye (see: [[retrobulbar block]]) or topical anesthetic eye drops. The former also provides paralysis of the eye muscles.
* Corneal incision – Two cuts are made at the margin of the clear cornea to allow insertion of instruments into the eye.
* [[Capsulorhexis]] – A needle or small pair of forceps is used to create a circular hole in the capsule in which the lens sits.
* [[Phacoemulsification]] – A handheld ultrasonic probe is used to break up and emulsify the lens into liquid using the energy of ultrasound waves. The resulting 'emulsion' is sucked away.
* Irrigation and aspiration – The cortex, which is the soft outer layer of the cataract, is aspirated or sucked away. Fluid removed is continually replaced with a saline solution to prevent collapse of the structure of the anterior chamber (the front part of the eye).
* Lens insertion – A plastic, foldable lens is inserted into the capsular bag that formerly contained the natural lens. Some surgeons also inject an antibiotic into the eye to reduce the risk of infection. The final step is to inject salt water into the corneal wounds to cause the area to swell and seal the incision.

A [[Cochrane review]] found little to no difference in visual acuity as a function of the size of incisions made for phacoemulsification in the range from ≤ 1.5&nbsp;mm to 3.0&nbsp;mm.<ref name="Jin">{{cite journal | vauthors = Jin C, Chen X, Law A, Kang Y, Wang X, Xu W, Yao K | title = Different-sized incisions for phacoemulsification in age-related cataract | journal = The Cochrane Database of Systematic Reviews | volume = 2017 | issue = 9 | article-number = CD010510 | date = September 2017 | pmid = 28931202 | pmc = 5665700 | doi = 10.1002/14651858.CD010510.pub2 }}</ref> Extracapsular cataract extraction (ECCE) consists of removing the lens manually, but leaving the majority of the capsule intact.<ref>{{citation |page=187 |chapter=Extracapsular Cataract Extraction |title=Essentials of Cataract Surgery | vauthors = Henderson B  |publisher=Slack |year=2007 |isbn=978-1-55642-802-9}}</ref> The lens is expressed through a 10- to 12-mm incision which is closed with [[Surgical suture|sutures]] at the end of surgery. ECCE is less frequently performed than phacoemulsification, but can be useful when dealing with very hard cataracts or other situations where emulsification is problematic. Manual small incision cataract surgery (MSICS) has evolved from ECCE. In MSICS, the lens is removed through a self-sealing scleral tunnel wound in the [[sclera]] which, ideally, is watertight and does not require suturing. Although "small", the incision is still markedly larger than the portal in phacoemulsification. This surgery is increasingly popular in the developing world where access to phacoemulsification is still limited.{{citation needed|date=September 2022}}

Intracapsular cataract extraction (ICCE) is rarely performed.<ref>{{citation |page=367 |title=The Eye in History | vauthors = Goes F  |publisher=JP Medical |year=2013 |isbn=978-93-5090-274-5}}</ref> The lens and surrounding capsule are removed in one piece through a large incision while pressure is applied to the [[vitreous membrane]].{{clarify|How and why is pressure applied?|date=December 2023}} The surgery has a high rate of complications.{{clarify|date=December 2023}}{{citation needed|date=September 2022}}

==Prognosis==

=== Postoperative care ===
[[File:Anterior capsular opacification.jpg|thumb|[[Slit lamp]] photo of anterior capsular opacification visible a few months after implantation of intraocular lens, magnified view]]
[[File:Africa Partnerships Vision 2020 2 (10665602364).jpg|thumb|A South African woman experiences newfound eyesight after a patch was removed after surgery to remove an eye cataract.]]
The postoperative recovery period (after removing the cataract) is usually short. The patient is usually ambulatory on the day of surgery, but is advised to move cautiously and avoid straining or heavy lifting for about a month. The eye is usually patched on the day of surgery and use of an eye shield at night is often suggested for several days after surgery.<ref name=vaughan />

In all types of surgery, the cataractous lens is removed and replaced with an artificial lens, known as an [[intraocular lens]], which stays in the eye permanently. Intraocular lenses are usually monofocal, correcting for either distance or near vision. Multifocal lenses may be implanted to improve near and distance vision simultaneously, but these lenses may increase the chance of unsatisfactory vision.<ref name="yanoff" />

===Complications===
{{main|Cataract surgery#Complications}}
Serious complications of cataract surgery include [[retinal detachment]] and [[endophthalmitis]].<ref>{{citation |title=Applied Pathology for Ophthalmic Microsurgeons |page=247 |year=2008 |chapter=Complications After Cataract Surgery |veditors=Naumann GO, Holbach LM, Kruse FE |publisher=Springer Science & Business |isbn=978-3-540-68366-7}}.</ref> In both cases, patients notice a sudden decrease in vision. In endophthalmitis, patients often describe pain. Retinal detachment frequently presents with unilateral [[visual field]] defects, blurring of vision, flashes of light, or floating spots.{{citation needed|date=September 2022}}

The risk of retinal detachment was estimated as about 0.4% within 5.5 years, corresponding to a 2.3-fold risk increase compared to naturally expected incidence, with older studies reporting a substantially higher risk. The incidence is increasing over time in a somewhat linear manner, and the risk increase lasts for at least 20 years after the procedure. Particular risk factors are younger age, male sex, longer axial length, and complications during surgery. In the highest risk group of patients, the incidence of pseudophakic retinal detachment may be as high as 20%.<ref name=Herrmann_2011>{{cite journal | vauthors = Herrmann W, Helbig H, Heimann H | title = [Pseudophakic retinal detachment] | journal = Klinische Monatsblätter für Augenheilkunde | volume = 228 | issue = 3 | pages = 195–200 | date = March 2011 | pmid = 21374539 | doi = 10.1055/s-0029-1246116 | s2cid = 260192934 }}</ref>

The risk of endophthalmitis occurring after surgery is less than one in 1000.<ref>{{cite journal | vauthors = Behndig A, Montan P, Stenevi U, Kugelberg M, Lundström M | title = One million cataract surgeries: Swedish National Cataract Register 1992–2009 | journal = Journal of Cataract and Refractive Surgery | volume = 37 | issue = 8 | pages = 1539–1545 | date = August 2011 | pmid = 21782099 | doi = 10.1016/j.jcrs.2011.05.021 }}</ref>

Corneal [[edema]] and cystoid macular edema are less serious but more common, and occur because of persistent swelling at the front of the eye in corneal edema or back of the eye in cystoid macular edema.<ref>{{citation |title=Ophthalmology Secrets in Color |vauthors=Gault J, Vander J |page=221 |year=2015 |publisher=Elsevier Health Sciences |isbn=978-0-323-37802-4}}.</ref> They are normally the result of excessive inflammation following surgery, and in both cases, patients may notice blurred, foggy vision. They normally improve with time and with application of anti-inflammatory drops. The risk of either occurring is around one in 100. It is unclear whether [[nonsteroidal anti-inflammatory drug|NSAIDs]] or corticosteroids are superior at reducing postoperative inflammation.<ref name="Juthani">{{cite journal | vauthors = Juthani VV, Clearfield E, Chuck RS | title = Non-steroidal anti-inflammatory drugs versus corticosteroids for controlling inflammation after uncomplicated cataract surgery | journal = The Cochrane Database of Systematic Reviews | volume = 2017 | issue = 7 | article-number = CD010516 | date = July 2017 | pmid = 28670710 | pmc = 5580934 | doi = 10.1002/14651858.CD010516.pub2 }}</ref>

Posterior capsular opacification, also known as after-cataract, is a condition in which months or years after successful cataract surgery, vision deteriorates or problems with glare and light scattering recur, usually due to thickening of the back or posterior capsule surrounding the implanted lens, so-called 'posterior lens capsule opacification'. Growth of natural lens cells remaining after the natural lens was removed may be the cause, and the younger the patient, the greater the chance of this occurring. Management involves cutting a small, circular area in the posterior capsule with targeted beams of energy from a laser, called [[Nd:YAG laser]] capsulotomy, after the type of laser used. The laser can be aimed very accurately, and the small part of the capsule which is cut falls harmlessly to the bottom of the inside of the eye. This procedure leaves sufficient capsule to hold the lens in place, but removes enough to allow light to pass directly through to the retina. Serious side effects are rare.<ref>{{cite web|url=http://www.rnib.org.uk/eyehealth/eyeconditions/conditionsac/Pages/cataract_lasersurgery.aspx|title=Posterior capsule opacification – why laser treatment is sometimes needed following cataract surgery|work=rnib.org.uk|url-status=live|archive-url=https://web.archive.org/web/20090917081625/http://www.rnib.org.uk/eyehealth/eyeconditions/conditionsac/Pages/cataract_lasersurgery.aspx|archive-date=2009-09-17|date=2014-02-19}}</ref> Posterior capsular opacification is common and occurs following up to one in four operations, but these rates are decreasing following the introduction of modern intraocular lenses together with a better understanding of the causes.{{citation needed|date=September 2022}}

[[Vitreous touch syndrome]] is a possible complication of intracapsular cataract extraction.<ref>{{cite web| vauthors = Banerjee K |title=A review and clinical evaluation of per-operative and post-operative complications in case of manual small incision cataract surgery and extracapsular cataract extraction with posterior chamber intra-ocular lens implantation|url=http://14.139.159.4:8080/jspui/bitstream/123456789/1638/1/CDMOPTH00032.pdf|access-date=1 June 2014|date=2006|archive-url=https://web.archive.org/web/20140605064801/http://14.139.159.4:8080/jspui/bitstream/123456789/1638/1/CDMOPTH00032.pdf|archive-date=5 June 2014}}</ref>

==Epidemiology==
[[File:Cataracts world map - DALY - WHO2004.svg|thumb|[[Disability-adjusted life years]] for cataracts per 100,000&nbsp;inhabitants in 2004:<ref>{{cite web |url=https://www.who.int/entity/healthinfo/global_burden_disease/gbddeathdalycountryestimates2004.xls |title=Death and DALY estimates for 2004 by cause for WHO Member States|publisher=who.int|format=xls |work=[[World Health Organization]]|year=2004}}</ref>
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Age-related cataracts are responsible for 51% of world blindness, about 20 million people.<ref name=WHO>{{cite web |title=Priority eye diseases: Cataract |work=Prevention of Blindness and Visual Impairment |publisher=World Health Organization |url=https://www.who.int/blindness/causes/priority/en/index1.html |archive-url=https://web.archive.org/web/20150524095804/http://www.who.int/blindness/causes/priority/en/index1.html |archive-date=2015-05-24 }}</ref> Globally, cataracts cause moderate to severe disability in 53.8&nbsp;million (2004), 52.2&nbsp;million of whom are in low and middle income countries.<ref>{{cite book |title=The global burden of disease: 2004 update. |year=2008 |publisher=World Health Organization |location=Geneva, Switzerland |isbn=978-92-4-156371-0 |page=35}}</ref>

In many countries, surgical services are inadequate, and cataracts remain the leading cause of blindness.<ref name=WHO/> Even where surgical services are available, low vision associated with cataracts may still be prevalent as a result of long waits for, and barriers to, surgery, such as cost, lack of information and transportation problems.<ref>{{Cite journal |last1=Batlle |first1=Juan Francisco |last2=Lansingh |first2=Van Charles |last3=Silva |first3=Juan Carlos |last4=Eckert |first4=Kristen Allison |last5=Resnikoff |first5=Serge |date=2014-08-01 |title=The Cataract Situation in Latin America: Barriers to Cataract Surgery |url=https://www.sciencedirect.com/science/article/abs/pii/S0002939414002220 |journal=American Journal of Ophthalmology |volume=158 |issue=2 |pages=242–250.e1 |doi=10.1016/j.ajo.2014.04.019 |pmid=24792101 |issn=0002-9394|url-access=subscription }}</ref>

In the United States, age-related lens changes have been reported in 42% between the ages of 52 and 64,<ref name="Sperduto">{{cite journal | vauthors = Sperduto RD, Seigel D | title = Senile lens and senile macular changes in a population-based sample | journal = American Journal of Ophthalmology | volume = 90 | issue = 1 | pages = 86–91 | date = July 1980 | pmid = 7395962 | doi = 10.1016/s0002-9394(14)75081-0 }}</ref> 60% between the ages 65 and 74,<ref>{{cite journal | vauthors = Kahn HA, Leibowitz HM, Ganley JP, Kini MM, Colton T, Nickerson RS, Dawber TR | title = The Framingham Eye Study. I. Outline and major prevalence findings | journal = American Journal of Epidemiology | volume = 106 | issue = 1 | pages = 17–32 | date = July 1977 | pmid = 879158 | doi = 10.1093/oxfordjournals.aje.a112428 }}</ref> and 91% between the ages of 75 and 85.<ref name="Sperduto"/> Cataracts affect nearly 22 million Americans age 40 and older. By age 80, more than half of all Americans have cataracts. Direct medical costs for cataract treatment are estimated at $6.8 billion annually.<ref>{{cite web|title=Eye Health Statistics at a Glance |url=http://www.aao.org/newsroom/upload/Eye-Health-Statistics-April-2011.pdf |archive-url=https://web.archive.org/web/20150317004848/http://www.aao.org/newsroom/upload/Eye-Health-Statistics-April-2011.pdf |archive-date=March 17, 2015 }}</ref>

In the eastern Mediterranean region, cataracts are responsible for over 51% of blindness. Access to eye care in many countries in this region is limited.<ref>{{cite web|title=Health Topics: Cataract|publisher=World Health Organization – Eastern Mediterranean Regional Office|url=http://www.emro.who.int/health-topics/cataract/|url-status=live|archive-url=https://web.archive.org/web/20130927045752/http://www.emro.who.int/health-topics/cataract/|archive-date=2013-09-27}}</ref> Childhood-related cataracts are responsible for 5–20% of world childhood blindness.<ref name=LiuWilkins2017>{{cite journal | vauthors = Liu YC, Wilkins M, Kim T, Malyugin B, Mehta JS | title = Cataracts | journal = Lancet | volume = 390 | issue = 10094 | pages = 600–612 | date = August 2017 | pmid = 28242111 | doi = 10.1016/S0140-6736(17)30544-5 | s2cid = 208790600 }}</ref>

Vision loss due to cataracts increases the risk of dementia in the elderly population, increases the likelihood of falls and road traffic accidents, and by detrimental effects on the quality of life increases mortality.<ref name="Fang et al 2022" >{{cite journal |last1=Fang |first1=Rui |last2=Yu |first2=Yang-Fan |last3=Li |first3=En-Jie |first4=Ning-Xin |last4=Lv |first5=Zhao-Chuan |last5=Liu |first6=Hong-Gang |last6=Zhou |first7=Xu-Dong |last7=Song |title=Global, regional, national burden and gender disparity of cataract: findings from the global burden of disease study 2019 |journal=BMC Public Health |volume=22 |number=2068 |date=2022 |page=2068 |doi=10.1186/s12889-022-14491-0 |pmid=36369026 |pmc=9652134 |doi-access=free }}</ref>

== History ==
{{See also|Cataract surgery#History}}

Cataract surgery was first described by the [[Ayurveda|Ayurvedic physician]], [[Suśruta]] (about 5th century BCE) in ''[[Sushruta Samhita]]'' in [[ancient India]]. Most of the methods focused on hygiene. Follow-up treatments include bandaging of the eye and covering the eye with warm [[butter]].<ref>{{cite book |url=https://books.google.com/books?id=v0oL8xDJ0VEC&pg=PA371 |title=The Eye in History |vauthors=Goes FJ |date=2013 |publisher=JP Medical Limited |isbn=978-93-5090-274-5 |page=371 |language=en}}</ref> Cataracts and their treatment in [[Ancient Rome]] are discussed in ''[[De Medicinae]]'' (29 CE) by the Latin encyclopedist [[Aulus Cornelius Celsus]].<ref>{{cite book |ol=5225311W |title=De Medicinae | vauthors = Celsus AC, Collier GF  |year=1831}}</ref> Archaeological evidence of eye surgery in the Roman era also exists.<ref>{{cite news |url=https://news.bbc.co.uk/1/hi/health/7194352.stm |title=The Romans carried out cataract ops |date=February 9, 2008 |work=BBC News | vauthors = Elliott J |url-status=live |archive-url= https://web.archive.org/web/20080218050244/http://news.bbc.co.uk/2/hi/health/7194352.stm |archive-date=February 18, 2008 }}</ref>

[[Galen|Galen of Pergamon]] (2nd century CE), the Greek physician, described an operation similar to modern cataract surgery. Using a needle-shaped instrument, Galen attempted to remove the cataract-affected lens of the eye.<ref>{{cite journal | pmc = 1034789 | pages=85–87 | volume=7 | issue=1 | journal=Med Hist | title=Galen: On Anatomical Procedures: the Later Books | doi=10.1017/s002572730002799x| year=1963 | vauthors = Keele KD }}</ref>

The [[Ophthalmology in medieval Islam|Arab ophthalmologist]] [[Ammar Al-Mawsili]], in his ''The Book of Choice in Ophthalmology'', written ''circa'' 1000 CE, wrote of his invention of a [[syringe]] and the technique of cataract extraction while [[experiment]]ing with it on a patient.<ref>{{Cite book|title=Origins of Neuroscience: A History of Explorations Into Brain Function| vauthors = Stanley F |year=1994|publisher=[[Oxford University Press]]|isbn=978-0-19-514694-3|page=70}}</ref>

In 1468 [[Abiathar Crescas]], a Jewish physician and astrologer of the [[Crown of Aragon]], famously removed the cataracts of King [[John II of Aragon]], restoring his eyesight.

===Etymology===
"Cataract" is derived from the [[Latin]] ''{{lang|la|cataracta}}'', itself from the [[Ancient Greek]] {{lang|grc|καταρράκτης}} (''{{lang|grc-Latn|katarrhaktēs}}'') 'waterfall'.<ref>{{cite book|chapter-url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dkatarra%2Fkths |chapter=καταρράκτης |archive-url=https://web.archive.org/web/20120405004553/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dkatarra%2Fkths |archive-date=2012-04-05 |first1=Henry George |last1=Liddell |first2=Robert |last2=Scott |title=A Greek-English Lexicon |title-link=A Greek–English Lexicon |via=Perseus}}</ref><ref>{{cite book|chapter-url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dkatara%2Fssw |chapter=καταράσσω |archive-url=https://web.archive.org/web/20120404220922/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dkatara%2Fssw |archive-date=2012-04-04 |first1=Henry George |last1=Liddell |first2=Robert |last2=Scott |title=A Greek-English Lexicon |title-link=A Greek–English Lexicon |via=Perseus}}</ref><ref name="DictionaryComCataract">{{cite web |url=https://www.dictionary.com/browse/cataract |title=cataract |work=Dictionary.com |publisher=Dictionary.com, LLC |access-date=1 April 2020}}</ref><ref name="OxfordCataractArch">{{cite web |url=http://oxforddictionaries.com/definition/english/cataract |archive-url=https://web.archive.org/web/20121008005743/http://oxforddictionaries.com/definition/english/cataract |title=cataract |work=Oxford Dictionaries |publisher=Oxford University Press |archive-date=8 October 2012 |access-date=1 April 2020}}</ref> As rapidly running water turns white, so the term may have been used metaphorically to describe the similar appearance of mature ocular opacities. In Latin, ''cataracta'' had the alternative meaning "[[portcullis]]"<ref>{{cite book|chapter-url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0059%3Aentry%3Dcataracta |chapter=cataracta |archive-url=https://web.archive.org/web/20120404221004/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0059%3Aentry%3Dcataracta |archive-date=2012-04-04 |first1=Charlton T. |last1=Lewis |first2=Charles |last2=Short |title=A Latin Dictionary |via=Perseus |title-link=A Latin Dictionary}}</ref> and the name possibly passed through French to form the English meaning "eye disease" (early 15th century), on the notion of "obstruction".<ref>{{cite web|url=http://www.etymonline.com/index.php?term=cataract |title=cataract |website=[[Online Etymology Dictionary]] |archive-url=https://web.archive.org/web/20071014103757/http://etymonline.com/index.php?term=cataract |archive-date=2007-10-14 }}</ref> Early Persian physicians called the term ''nazul-i-ah'', or "descent of the water"—vulgarised into waterfall disease or cataract—believing such blindness to be caused by an outpouring of corrupt [[humorism|humour]] into the eye.<ref>[http://wordcraft.infopop.cc/eve/forums/a/tpc/f/756604565/m/2881057435 Mistaken Science – Topic Powered by eve community] {{webarchive|url=https://web.archive.org/web/20080622143811/http://wordcraft.infopop.cc/eve/forums/a/tpc/f/756604565/m/2881057435 |date=2008-06-22 }}, Wordcraft Forums, wordcraft.infopop.cc</ref>

==Research==
[[acetylcarnosine|N-Acetylcarnosine]] drops have been investigated as a medical treatment for cataracts. The drops are believed to work by reducing [[oxidation]] and [[glycation]] damage in the lens, particularly reducing [[crystallin]] crosslinking.<ref>{{cite journal | vauthors = Williams DL, Munday P | title = The effect of a topical antioxidant formulation including N-acetyl carnosine on canine cataract: a preliminary study | journal = Veterinary Ophthalmology | volume = 9 | issue = 5 | pages = 311–316 | year = 2006 | pmid = 16939459 | doi = 10.1111/j.1463-5224.2006.00492.x }}</ref><ref>{{cite journal | vauthors = Guo Y, Yan H | title = [Preventive effect of carnosine on cataract development] | journal = Yan Ke Xue Bao = Eye Science | volume = 22 | issue = 2 | pages = 85–88 | date = June 2006 | pmid = 17162883 }}</ref> Some benefit has been shown in small manufacturer-sponsored randomized controlled trials but further independent corroboration is still required.<ref>{{cite journal | vauthors = Toh T, Morton J, Coxon J, Elder MJ | title = Medical treatment of cataract | journal = Clinical & Experimental Ophthalmology | volume = 35 | issue = 7 | pages = 664–671 | year = 2007 | pmid = 17894689 | doi = 10.1111/j.1442-9071.2007.01559.x | s2cid = 43125880 }}</ref>

[[Mode-locking|Femtosecond laser mode-locking]], used during cataract surgery, was originally used to cut accurate and predictable flaps in [[LASIK]] surgery, and has been introduced to cataract surgery. The incision at the junction of the sclera and cornea and the hole in capsule during capsulorhexis, traditionally made with a handheld blade, needle, and forceps, are dependent on skill and experience of the surgeon. Sophisticated three-dimensional images of the eyes can be used to guide lasers to make these incisions. A [[Nd:YAG laser]] can also then break up the cataract as in phacoemulsification.<ref>{{cite journal | vauthors = Friedman NJ, Palanker DV, Schuele G, Andersen D, Marcellino G, Seibel BS, Batlle J, Feliz R, Talamo JH, Blumenkranz MS, Culbertson WW | title = Femtosecond laser capsulotomy | journal = Journal of Cataract and Refractive Surgery | volume = 37 | issue = 7 | pages = 1189–1198 | date = July 2011 | pmid = 21700099 | doi = 10.1016/j.jcrs.2011.04.022 | s2cid = 3860204 }} [http://www.stanford.edu/~palanker/publications/fs%20capsulotomy%20JCRS%202011.pdf as PDF] {{webarchive|url=https://web.archive.org/web/20120914073521/http://www.stanford.edu/~palanker/publications/fs%20capsulotomy%20JCRS%202011.pdf |date=2012-09-14 }} The authors declare a financial interest in a company producing femtosecond laser equipment.</ref>

[[Stem cells]] have been used in a clinical trial, with results submitted in 2014 and published in March 2016, for [[lens regeneration]] in twelve children under the age of two with cataracts present at birth.<ref name=NHS2016>{{cite web|title=Stem cells used to repair children's eyes after cataracts|url=http://www.nhs.uk/news/2016/03March/Pages/Childrens-eyes-damaged-by-cataracts-repaired-by-stem-cells.aspx |publisher=NHS |access-date=11 March 2016|date=March 10, 2016|url-status=live |archive-url=https://web.archive.org/web/20160311073154/http://www.nhs.uk/news/2016/03March/Pages/Childrens-eyes-damaged-by-cataracts-repaired-by-stem-cells.aspx |archive-date=11 March 2016}}</ref> The children were followed for six months, so it is unknown what the long-term results have been, and it is unknown if this procedure would work in adults.<ref name=NHS2016/>

== See also ==
{{Portal|Medicine}}
* {{annotated link|Galactosemic cataract}}
* {{annotated link|Intraocular lens}}

== References ==
{{Reflist}}

==Further reading==
* {{cite journal | vauthors = Truscott RJ, Friedrich MG | title = Molecular Processes Implicated in Human Age-Related Nuclear Cataract | journal = Investigative Ophthalmology & Visual Science | volume = 60 | issue = 15 | pages = 5007–5021 | date = December 2019 | pmid = 31791064 | pmc = 7043214 | doi = 10.1167/iovs.19-27535 | oclc = 1141250841 }}

== External links ==
* [http://dro.hs.columbia.edu/lc1.htm Pictures of different types of cataracts] {{Webarchive|url=https://web.archive.org/web/20130327142432/http://dro.hs.columbia.edu/lc1.htm |date=2013-03-27 }}

{{Medical resources
| eMedicine_mult  = {{EMedicine2|article|1210914}}
| ICD10           = {{ICD10|H|25||h|25}}-{{ICD10|H|26||h|25}}, {{ICD10|H|28||h|25}}, {{ICD10|Q|12|0|q|12}}
| ICD9            = {{ICD9|366}}
| DiseasesDB      = 2179
| MedlinePlus     = 001001
| eMedicineSubj   =
| eMedicineTopic  =
| MeSH            = D002386
| SNOMED CT       = 128306009
}}
{{Eye pathology}}
{{Authority control}}

[[Category:Aging-associated diseases]]
[[Category:Blindness]]
[[Category:Eye diseases]]
[[Category:Disorders of lens]]
[[Category:Eye]]
[[Category:Ophthalmology]]
[[Category:Vision]]
[[Category:Wikipedia medicine articles ready to translate]]
[[Category:Wikipedia neurology articles ready to translate]]