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| '''Editor-in-Chief:''' Kenneth J. Hoffer, M.D. [mailto:KHofferMD@aol.com], Clinical Professor of Ophthalmology, UCLA, St. Mary's Eye Center | | '''Editor-in-Chief:''' Kenneth J. Hoffer, M.D. [mailto:KHofferMD@aol.com], Clinical Professor of Ophthalmology, UCLA, St. Mary's Eye Center |
| | ==[[Cataract overview|Overview]]== |
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| ==Overview== | | ==[[Cataract historical perspective|Historical Perspective]]== |
| [[Image:Human eye cross-sectional view grayscale.png|thumb|220px|left|Human eye cross-sectional view, showing position of human lens. Courtesy [[National Institutes of Health|NIH]] [[National Eye Institute]]]] | |
| [[Image:Eyesection.gif|thumb|left|216px|Human [[eye]] cross-sectional view, showing position of human lens. Courtesy [[National Institutes of Health|NIH]] [[National Eye Institute]]]]
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| A '''cataract''' a cloudy lens that does not transmit light signals to the retina. Early on in the development of age-related cataract the power of the crystalline 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</ref> Moreover, with time the cataract cortex liquefies to form a milky white fluid in a '''Morgagnian Cataract''', and 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 [[couching]]) in ancient times were regarded as a blessing from the heavens, because it restored some perception of light in the bilaterally affected patients.
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| ''Cataract'' derives from the Latin ''cataracta'' meaning "waterfall" and the 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]</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</ref>, so it is also possible that the name came about through the sense of "obstruction".
| | ==[[Cataract pathophysiology|Pathophysiology]]== |
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| == Causes == | | ==[[Cataract causes|Causes]]== |
| Cataracts develop from a variety of reasons, including long-term ultraviolet exposure, exposure to radiation, secondary effects of diseases such as [[diabetes]], 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}}</ref> Cataracts are also unusually common in persons exposed to infrared radiation, such as glassblowers who suffer from "exfoliation syndrome". Exposure to microwave radiation can cause cataracts.
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| Cataracts may be partial or complete, stationary or progressive, hard or soft.
| | ==[[Cataract differential diagnosis|Differentiating Cataract from other Diseases]]== |
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| Some drugs can induce cataract development, such as [[Corticosteroids]]<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>
| | ==[[Cataract epidemiology and demographics|Epidemiology and Demographics]]== |
| and [[Ezetimibe]]
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| There are various types of cataracts, 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).
| | ==[[Cataract risk factors|Risk Factors]]== |
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| ==Epidemiology== | | ==[[Cataract natural history, complications and prognosis|Natural History, Complications and Prognosis]]== |
| Cataracts are the leading cause of blindness in the world.<ref>https://web.emmes.com/study/areds/mopfiles/chp2_mop.pdf</ref>
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| 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"/>.
| | ==Diagnosis== |
| | [[Cataract history and symptoms|History and Symptoms]] | [[Cataract physical examination|Physical Examination]] | [[Cataract laboratory findings|Laboratory Findings]] | [[Cataract other imaging findings|Other Imaging Findings]] | [[Cataract other diagnostic studies|Other Diagnostic Studies]] |
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| ==Cataract surgery== | | ==Treatment== |
| {{main|Cataract surgery}}
| | [[Cataract medical therapy|Medical Therapy]] | [[Cataract surgery|Surgery]] | [[Cataract primary prevention|Primary Prevention]] | [[Cataract secondary prevention|Secondary Prevention]] | [[Cataract cost-effectiveness of therapy|Cost-Effectiveness of Therapy]] | [[Cataract future or investigational therapies|Future or Investigational Therapies]] |
| [[Image:Cataract surgery.jpg|thumb|216px|left|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]] | |
| The most effective and common treatment is to surgically remove the cloudy lens. There are two types of [[surgery]] that can be used to remove cataracts: extra-capsular (extracapsular cataract extraction, or ECCE) and intra-capsular (intracapsular cataract extraction, or ICCE).
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| 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.
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| 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.
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| 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. | |
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| Complications after cataract surgery, including endophthalmitis, posterior capsular opacification and [[retinal detachment]], are possible.
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| 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.
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| ==Prevention==
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| 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 p.37 quoting Javitt, J. C., F. Wang, and S. K. West. “Blindness Due to Cataract: Epidemiology and Prevention.” Annual Review of Public Health 17 (1996): 159-77.</ref> Regular intake of [[antioxidants]] (such as vitamin C and E) is theoretically helpful, but this has not been proven.
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| == Recent research ==
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| 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}}</ref>
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| 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>
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| ==Types of cataracts==
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| [[Image:Cataracts due to Congenital Rubella Syndrome (CRS) PHIL 4284 lores.jpg|thumb|250px|left|Bilateral cataracts in an infant due to [[Congenital rubella syndrome]], courtesy CDC]]
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| The following is a classification of the various types of cataracts. This is not comprehensive and other unusual types may be noted.
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| :*classified by etiology
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| :*Age-related cataract
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| ::*Immature Senile Cataract (IMSC) - partially opaque lens, [[Optic disc|disc]] view hazy
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| ::*Mature Senile Cataract (MSC) - Completely opaque lens, no disc view
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| ::*Hypermature Senile Cataract (HMSC) - Liquefied cortical matter: '''Morgagnian Cataract'''
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| :*Congenital cataract
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| ::*Sutural cataract
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| ::*Lamellar cataract
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| ::*Zonular cataract
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| ::*Total cataract
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| ::* secondary cataract
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| [[Image:Anterior capsular opacification.jpg|thumb|250px|left|[[Slit lamp]] photo of Anterior capsular opacification visible a few months after implantation of Intraocular lens in eye, magnified view]]
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| ::*Drug-induced cataract (e.g. Corticosteroids)
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| :*Traumatic cataract
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| ::*Blunt trauma (capsule usually intact)
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| ::*Penetrating trauma (capsular rupture & leakage of lens material - calls for an emergency surgery for extraction of lens and leaked material to minimize further damage)
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| *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)
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| :*Anterior cortical cataract
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| :*Anterior polar cataract
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| :*Anterior subcapsular cataract
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| [[Image:Posterior capsular opacification on retroillumination.jpg|thumb|left|250px|[[Slit lamp]] photo of Posterior capsular opacification visible a few months after implantation of Intraocular lens in eye, seen on retroillumination]]
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| :*Nuclear cataract - Grading correlates with hardness & difficulty of surgical removal
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| ::*1 - Grey
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| ::*2 - Yellow
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| ::*3 - Amber
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| ::*4 - Brown/Black (Note: "Black cataract" translated in some languages (like Hindi) refers to [[Glaucoma]], not the color of the lens nucleus)
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| :*Posterior cortical cataract
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| :*Posterior polar cataract (importance lies in higher risk of complication - posterior capsular tears during surgery)
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| :*Posterior subcapsular cataract (PSC) (clinically common)
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| ::*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.
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| ==Associations with systemic conditions==
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| *[[Genetic disorders|Chromosomal disorder]]s
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| :*[[Alport's syndrome]]
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| :*[[Cri-du-chat syndrome]]
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| :*Conradi's syndrome
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| :*Myotonia dystrophica
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| :*[[Patau's syndrome]]
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| :*Schmid-Fraccaro syndrome
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| :*[[Trisomy 18]] ([[Edward's syndrome]])
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| :*[[Turner's syndrome]]
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| *Disease of the [[skin]] and [[mucous membranes]]
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| :*[[Atopic dermatitis]]
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| :*Basal-cell nevus syndrome
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| :*[[Ichthyosis]]
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| :*[[Pemphigus]]
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| *[[Metabolic disease|Metabolic]] and nutrition diseases
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| :*[[Aminoaciduria]] ([[Lowe's syndrome]])
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| :*[[Diabetes mellitus]]
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| :*[[Fabry's disease]]
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| :*[[Galactosemia]]
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| :*[[Homocystinuria]]
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| :*[[Hypervitaminosis D]]
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| :*[[Hyperparathyroidism]]
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| :*[[Hypothyroidism]]
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| :*[[Mucopolysaccharidoses]]
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| :*[[Wilson's disease]]
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| *[[Infectious disease]]s
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| :*Congenital
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| ::*[[Congential herpes simplex]]
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| ::*[[Congenital syphilis]]
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| ::*[[Cytomegalic inclusion disease]]
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| ::*[[Rubella]]
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| :*Others
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| ::*[[Cysticercosis]]
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| ::*[[Leprosy]]
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| ::*[[Onchocerciasis]]
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| ::*[[Toxoplasmosis]]
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| *Toxic substances introduced systemically
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| :*[[Corticosteroids]]
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| :*[[Haloperidol]]
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| :*[[Miotics]]
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| :*Triparanol
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| | == Case Studies == |
| | [[Cataract case study one|Case #1]] |
| ==References== | | ==References== |
| {{Reflist|2}} | | {{Reflist|2}} |
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| *Pavan-Langston, Deborah (1990). ''Manual of Ocular Diagnosis and Therapy.'' Little, Brown and Company.
| | ==Related Chapters== |
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| ==See also== | |
| *[[List of eye diseases and disorders]] | | *[[List of eye diseases and disorders]] |
| *[[List of systemic diseases with ocular manifestations]] | | *[[List of systemic diseases with ocular manifestations]] |