Cataract
88931
225768575
2008-07-15T09:03:56Z
Graham87
194203
/* Associations with systemic conditions */ typo
{{citation style|date=August 2007}}
{{DiseaseDisorder infobox |
Name = Cataract |
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|
Image = Cataract in human eye.png|
Caption = Magnified view of cataract in human eye, seen on [[eye examination | examination]] with a [[slit lamp]] using diffuse illumination|
}}
[[Image:Human eye cross-sectional view grayscale.png|thumb|220px|right|Human eye cross-sectional view, showing position of human lens. Courtesy [[National Institutes of Health|NIH]] [[National Eye Institute]]]]
[[Image:Eyesection.gif|thumb|right|216px|Human [[eye]] cross-sectional view, showing position of human lens. Courtesy [[National Institutes of Health|NIH]] [[National Eye Institute]]]]
{{otheruses}}
A '''cataract''' is a clouding that develops in the [[lens (anatomy)|crystalline lens]] of the [[eye]] or in its envelope, varying in degree from slight to complete [[Opacity (optics)|opacity]] and obstructing the passage of light. Early in the development of age-related cataract the power of the lens may be increased, causing near-sightedness ([[myopia]]), and the gradual yellowing and opacification of the lens may reduce the perception of blue colours. Cataracts typically progress slowly to cause [[vision loss]] and are potentially [[blindness|blinding]] if untreated.<ref>[http://www.aafp.org/afp/990700ap/99.html Common Causes of Vision Loss in Elderly Patients - July 1999 - American Academy of Family Physicians<!-- Bot generated title -->]</ref>
A '''senile cataract''', occurring in the aged, is characterized by an initial opacity in the lens, subsequent swelling of the lens and final shrinkage with complete loss of transparency.<ref>[http://www.emedicine.com/OPH/topic49.htm eMedicine - Cataract, Senile : Article by Vicente Victor D Ocampo.] From eMedicine The Continually Updated Clinical Reference</ref> Moreover, with time the cataract cortex liquefies to form a milky white fluid in a '''Morgagnian cataract''', which can cause severe inflammation if the lens capsule ruptures and leaks. Untreated, the cataract can cause [[glaucoma|phacomorphic glaucoma]]. Very advanced cataracts with weak [[zonules]] are liable to dislocation anteriorly or posteriorly. Such spontaneous posterior dislocations (akin to the historical surgical procedure of [[Cataract_surgery#History|couching]]) in ancient times were regarded as a blessing from the heavens, because some perception of light was restored in the cataractous patients.
''Cataract'' derives from the [[Latin]] ''cataracta'' meaning "waterfall" and the [[Greek language|Greek]] ''kataraktes'' and ''katarrhaktes'', from ''katarassein'' meaning "to dash down" (''kata''-, "down"; ''arassein'', "to strike, dash"<ref>[http://dictionary.reference.com/wordoftheday/archive/2003/10/29.html Dictionary.com/Word of the Day Archive/cataract<!-- Bot generated title -->]</ref>). As rapidly running water turns white, the term may later have been used metaphorically to describe the similar appearance of mature ocular opacities. In Latin, ''cataracta'' had the alternate meaning "[[portcullis]]",<ref>[http://www.etymonline.com/index.php?term=cataract Online Etymology Dictionary<!-- Bot generated title -->]</ref> so it is also possible that the name came about through the sense of "obstruction". 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 humour into the eye.<ref>[http://wordcraft.infopop.cc/eve/forums/a/tpc/f/756604565/m/2881057435 Mistaken Science - Topic Powered by eve community.] Wordcraft Forums</ref> In dialect English a cataract is called a ''pearl'', as in "pearl eye" and "pearl-eyed".<ref>[http://machaut.uchicago.edu/CGI-BIN/WEBSTER.page.sh?page=1055 Webster's Revised Unabridged Dictionary (1913 edition).] Public Reference Tools - The ARTFL Project (American and French Research on the Treasury of the French Laanguage), University of Chicago</ref>
== Causes ==
Cataracts develop from a variety of reasons, including long-term ultraviolet exposure, exposure to radiation, secondary effects of diseases such as [[diabetes]], hypertension and advanced age; they are usually a result of [[Denaturation (biochemistry)|denaturation]] of lens [[protein]]s. [[genetics|Genetic]] factors are often a cause of [[congenital]] cataracts and positive family history may also play a role in predisposing someone to cataracts at an earlier age, a phenomenon of "anticipation" in pre-senile cataracts. Cataracts may also be produced by [[eye injury]] or [[physical trauma]]. A study among [[Icelandair]] pilots showed commercial airline pilots as three times more likely to develop cataracts than people with non-flying jobs. This is thought to be caused by excessive exposure to radiation coming from [[outer space]].<ref>{{cite journal | last = Rafnsson | first = V | coauthors = Olafsdottir E, Hrafnkelsson J, Sasaki H, Arnarsson A, Jonasson F | title = Cosmic radiation increases the risk of nuclear cataract in airline pilots: a population-based case-control study | journal = Arch Ophthalmol | volume = 123 | pages = 1102–1105 | doi = 10.1001/archopht.123.8.1102 | year = 2005 | pmid = 16087845}}</ref> Cataracts are also unusually common in persons exposed to infrared radiation, such as [[Glassblowing|glassblowers]] who suffer from "exfoliation syndrome". Exposure to microwave radiation can cause cataracts.
Cataracts may be partial or complete, stationary or progressive, hard or soft.
Some drugs can induce cataract development, such as [[Corticosteroid]]s<ref name=spencer>{{cite journal |author=SPENCER R, ANDELMAN S |title=Steroidsarebad Cataracts. Posterior Subcapsular Cataract Formation In Rheumatoid Arthritis Patients On Long Term Steroid Therapy |journal=Arch Ophthalmol |volume=74 |issue= |pages=38–41 |year= |pmid=14303339}}</ref>
and [[Ezetimibe]]{{Fact|date=July 2007}} and [[Seroquel]].
There are various types of cataract, e.g. nuclear, cortical, mature, hypermature. Cataracts are also classified by their location, e.g. posterior (classically due to steroid use<ref name=spencer/><ref>{{cite journal |author=Greiner J, Chylack L |title=Posterior subcapsular cataracts: histopathologic study of steroid-associated cataracts |journal=Arch Ophthalmol |volume=97 |issue=1 |pages=135–44 |year=1979 |pmid=758890}}</ref>) and anterior (common (senile) cataract related to aging).
==Epidemiology==
Age-related cataract is responsible for 48% of world blindness, which represents about 18 million people, according to the World Health Organization (WHO).<ref>[http://www.who.int/blindness/causes/priority/en/index1.html WHO | Priority eye diseases.]</ref> In many countries surgical services are inadequate, and cataracts remain the leading cause of blindness. As populations age, the number of people with cataracts is growing. Cataracts are also an important cause of low vision in both developed and developing countries. Even where surgical services are available, low vision associated with cataracts may still be prevalent, as a result of long waits for operations and barriers to surgical uptake, such as cost, lack of information and transportation problems.
In the United States, age-related lenticular changes have been reported in 42% of those between the ages of 52 to 64,<ref name="Sperduto">Sperduto RD, Seigel D. Sperduto RD, Seigel D. "Senile lens and senile macular changes in a population-based sample." ''Am J Ophthalmol.'' 1980 Jul;90(1):86-91. PMID 7395962.</ref> 60% of those between the ages 65 and 74,<ref>Kahn HA, Leibowitz HM, Ganley JP, Kini MM, Colton T, Nickerson RS, Dawber TR. "The Framingham Eye Study. I. Outline and major prevalence findings." ''Am J Epidemiol.'' 1977 Jul;106(1):17-32. PMID 879158.</ref> and 91% of those between the ages of 75 and 85.<ref name="Sperduto"/>
==Cataract surgery==
{{main|Cataract surgery}}
[[Image:Cataract surgery.jpg|thumb|216px|right|Cataract surgery, using a temporal approach phacoemulsification probe (in right hand) and "chopper" (in left hand) being done under operating microscope at a Navy medical center]]
When a cataract is "ripe" (sufficiently developed to be removed by surgery), the most effective and common treatment is to make an incision (''capsulotomy'') into the capsule of the cloudy lens in order to surgically remove the lens. There are two types of [[eye surgery]] that can be used to remove cataracts: extra-capsular (extracapsular cataract extraction, or ECCE) and intra-capsular (intracapsular cataract extraction, or ICCE).
Extra-capsular (ECCE) surgery consists of removing the lens but leaving the majority of the [[lens capsule]] intact. [[High frequency]] [[sound wave]]s ([[phacoemulsification]]) are sometimes used to break up the lens before extraction.
Intra-capsular (ICCE) surgery involves removing the entire lens of the eye, including the lens capsule, but it is rarely performed in modern practice.
In either extra-capsular surgery or intra-capsular surgery, the cataractous lens is removed and replaced with a [[plastic]] lens (an [[intraocular lens]] implant) which stays in the eye permanently.
Cataract operations are usually performed using a [[local anaesthetic]] and the patient is allowed to go home the same day. Recent improvements in intraocular technology now allow cataract patients to choose a multifocal lens to create a visual environment in which they are less dependent on glasses. Under some medical systems multifocal lenses cost extra. Traditional intraocular lenses are monofocal.
Complications are possible after cataract surgery, including [[endophthalmitis]], [[posterior capsular opacification]] and [[retinal detachment]].
In ICCE there is the issue of the Jack in the box phenomenon where the patient has to wear [[aphakic]] glasses - alternatives include contact lenses but these can prove to be high maintenance, particularly in dusty areas.
==Prevention==
Although cataracts have no scientifically proven prevention, it is sometimes said that wearing [[ultraviolet]]-protecting [[sunglasses]] may slow the development of cataracts.<ref>Epidemiology. 2003 Nov;14(6):707-12. Sun exposure as a risk factor for nuclear cataract</ref><ref>[http://www.nei.nih.gov/nehep/pdf/NEHEP_5_year_agenda_2006.pdf J.C. Javitt, F. Wang and S. K. West, “Blindness Due to Cataract: Epidemiology and Prevention.”] Annual Review of Public Health 17 (1996): 159-77. 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> Regular intake of [[antioxidants]] (such as vitamin A, C and E) is theoretically helpful, but taking them as a supplement has been shown to have no benefit.<ref>A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E and beta carotene for age-related cataract and vision loss: AREDS report no. 9. Arch Ophthalmol. 2001 Oct;119(10):1439-52</ref>
== Recent research ==
Although [[statins]] are known for their ability to lower lipids, they are also believed to have antioxidant qualities. It is believed that oxidative stress plays a role in the development of nuclear cataracts, which are the most common type of age-related cataract. To explore the relationship between nuclear cataracts and statin use, a group of researchers took a group of 1299 patients who were at risk of developing nuclear cataracts and gave some of them statins. Their results suggest that statin use in a general population may be associated with a lower risk of developing nuclear cataract disease.<ref>{{ cite journal | first = Barbara | last = Klein | coauthors = Ronald Klein, Kristine Lee, and Lisa Grady | title = Statin Use and Incident Nuclear Cataract | journal = Journal of the American Medical Association | volume = 295 | issue = 23 | pages = 2752–2758 | doi = 10.1001/jama.295.23.2752 | year = 2006 | pmid = 16788130}}</ref>
Research is scant and mixed but weakly positive for the nutrients lutein and zeaxanthin.<ref>Nutrition. 2003 Jan;19(1):21 Lutein, but not alpha-tocopherol, supplementation improves visual function] in patients with age-related cataracts: a 2-y double-blind, placebo-controlled pilot study</ref><ref>Invest Ophthalmol Vis Sci. 2006 Sep;47(9):3783-6. Lutein and zeaxanthin and the risk of cataract: the Melbourne visual impairment project</ref><ref>Invest Ophthalmol Vis Sci. 2006 Jun;47(6):2329-35. Plasma lutein and zeaxanthin and other carotenoids as modifiable risk factors for age-related maculopathy and cataract: the POLA Study</ref><ref>J Am Coll Nutr. 2004 Dec;23(6 Suppl):567S-587S Lutein and zeaxanthin and their potential roles in disease prevention</ref> Bilberry extract shows promise in rat models <ref>Dietary supplementation with bilberry extract prevents macular degeneration and cataracts in senesce-accelerated OXYS rats Adv Gerontol. 2005;16:76-9</ref><ref>Yamakoshi J, et al. J Agric Food Chem. 2002 Aug 14;50(17):4983-8. </ref> and in clinical studies.<ref>Ann Ottalmol Clin Ocul, 1989</ref>
==Types of cataracts==
[[Image:Cataracts due to Congenital Rubella Syndrome (CRS) PHIL 4284 lores.jpg|thumb|250px|Bilateral cataracts in an infant due to [[Congenital rubella syndrome]], courtesy CDC]]
The following is a classification of the various types of cataracts. This is not comprehensive and other unusual types may be noted.
*Classified by etiology
:*Age-related cataract
::*Immature Senile Cataract (IMSC) - partially opaque lens, [[Optic disc|disc]] view hazy
::*Mature Senile Cataract (MSC) - Completely opaque lens, no disc view
::*Hypermature Senile Cataract (HMSC) - Liquefied cortical matter: '''Morgagnian Cataract'''
:*Congenital cataract
::*Sutural cataract
::*Lamellar cataract
::*[[Zonular cataract and nystagmus | Zonular cataract]]
::*Total cataract
:*Secondary cataract
[[Image:Anterior capsular opacification.jpg|thumb|250px|[[Slit lamp]] photo of Anterior capsular opacification visible a few months after implantation of Intraocular lens in eye, magnified view]]
::*Drug-induced cataract (e.g. Corticosteroids)
:*Traumatic cataract
::*Blunt trauma (capsule usually intact)
::*Penetrating trauma (capsular rupture & leakage of lens material - calls for an emergency surgery for extraction of lens and leaked material to minimize further damage)
*Classified by location of opacity within lens structure (However, mixed morphology is quite commonly seen, e.g. PSC with nuclear changes & cortical spokes of cataract)
:*Anterior cortical cataract
:*Anterior polar cataract
:*Anterior subcapsular cataract
[[Image:Posterior capsular opacification on retroillumination.jpg|thumb|250px|[[Slit lamp]] photo of Posterior capsular opacification visible a few months after implantation of Intraocular lens in eye, seen on retroillumination]]
:*Nuclear cataract - Grading correlates with hardness & difficulty of surgical removal
::*1 - Grey
::*2 - Yellow
::*3 - Amber
::*4 - Brown/Black (Note: "Black cataract" translated in some languages (like [[Hindi]]) refers to [[Glaucoma]], not the color of the lens nucleus)
:*Posterior cortical cataract
:*Posterior polar cataract (importance lies in higher risk of complication - posterior capsular tears during surgery)
:*Posterior subcapsular cataract (PSC) (clinically common)
::*After-cataract - posterior capsular opacification subsequent to a successful extracapsular cataract surgery (usually within 3 months - 2 years) with or without IOL implantation. Requires a quick & painless office procedure with [[Nd:YAG laser]] capsulotomy to restore optical clarity.
==Associations with systemic conditions==
*[[Genetic disorders|Chromosomal disorder]]s
:*[[Alport's syndrome]]
:*[[Cri-du-chat syndrome]]
:*[[Conradi's syndrome]]
:*[[Myotonic dystrophy]]
:*[[Patau's syndrome]]
:*[[Schmid-Fraccaro syndrome]]
:*[[Trisomy 18]] ([[Edward's syndrome]])
:*[[Turner's syndrome]]
*Disease of the [[skin]] and [[mucous membranes]]
:*[[Atopic dermatitis]]
:*[[Basal-cell nevus syndrome]]
:*[[Ichthyosis]]
:*[[Pemphigus]]
*[[Metabolic disease|Metabolic]] and [[nutrition disease]]s
:*[[Aminoaciduria]] ([[Lowe's syndrome]])
:*[[Diabetes mellitus]]
:*[[Fabry's disease]]
:*[[Galactosemia]] / [[Galactosemic Cataract]]
:*[[Homocystinuria]]
:*[[Hypervitaminosis D]]
:*[[Hyperparathyroidism]]
:*[[Hypothyroidism]]
:*[[Mucopolysaccharidoses]]
:*[[Wilson's disease]]
*[[Infectious disease]]s
:*Congenital
::*[[Congenital herpes simplex]]
::*[[Congenital syphilis]]
::*[[Cytomegalic inclusion disease]]
::*[[Rubella]]
:*Others
::*[[Cysticercosis]]
::*[[Leprosy]]
::*[[Onchocerciasis]]
::*[[Toxoplasmosis]]
*Toxic substances introduced systemically
:*[[Corticosteroids]]
:*[[Haloperidol]]
:*[[Miotics]]
:*[[Triparanol]]
==See also==
*[[List of eye diseases and disorders]]
*[[List of systemic diseases with ocular manifestations]]
==References and notes==
*Pavan-Langston, Deborah (1990). ''Manual of Ocular Diagnosis and Therapy.'' Little, Brown and Company.
{{Reflist|2}}
== External links ==
*[http://www.nei.nih.gov/health/cataract/cataract_facts.asp Cataract] Resource Guide from the National Eye Institute (NEI).
*[http://www.emedicinehealth.com/articles/14319-1.asp eMedicine Health]
*[http://www.surgery-sugery.com/cataract-surgery.php Video of Cataract Surgery]
*[http://www.childhoodcataracts.org.uk The Childhood Cataract Network]
*[http://www.wellsphere.com/wellmix360/Cataracts Cataract Overview Page]
{{Eye pathology}}
[[Category:Aging-associated diseases]]
[[Category:Blindness]]
[[Category:Ophthalmology]]
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