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*# Ocular conditions with associated anomalies e.g. [[Retinopathy of Prematurity]] and some types of retinitis pigmentosa. 
*# Ocular conditions with associated anomalies e.g. [[Retinopathy of Prematurity]] and some types of retinitis pigmentosa. 
*# Secondary to metabolic disorders e.g. [[Galactosemia]] and [[Wilson's disease|Wilson’s disease]]  
*# Secondary to metabolic disorders e.g. [[Galactosemia]] and [[Wilson's disease|Wilson’s disease]]  
* Degenerative or "Age Related" (senile)- Most adults have some degree of opacification of the lens and therefore technically exhibit cataract. 
*# ''Subcapsular ''Anterior subcapsular cataract (directly under the capsule) is associated with fibrous metaplasia of anterior lens epithelium. Posterior subcapsular cataract (c''upuliform'') lies just in front of posterior capsule and is associated with posterior migration of epithelial cells. 
*# Cortical  Corticalcataract commonly develops as radial or spoke shaped “water-clefts” (''cuneiform)'' togther with vacuoles. Cuneiform changes affect anterior, posterior and equatorial cortex affected.
*# ''Nuclear sclerosis '' Nuclear cataract is an exacerbation of the normal ageing of lens nucleus and appears as a yellowing of the nucleus. 
*'''Traumatic '''  Trauma is the commonest cause of unilateral cataract in young individuals''.'' Opacities can be the result of various injuries including penetrating injury. Concussion to the eye may cause the iris to be flattened against the lens leaving a Vossius’ ring. 
*'''Secondary '''  Cataract can occur secondary to systemic disease or syndromes including metabolic disorders and due to local disease (ocular).   Many conditions can cause or be associated with cataract 
*#Diabetes - Diabetes mellitus can cause an exacerbation of the progression of age related degenerative changes. So-called (classical) diabetic cataract occurs during an acute and untreated hyperglycaemic episode and takes the form of cortical “snowflakes”. These occur due to osmotic over-hydration of the lens and can be anterior and/or posterior in position. 
*#Galactosaemia - This metabolic disease produces an “oil droplet” cataract. 
*#Wilson’s disease (hepatolenticular degeneration) - This is an anomaly of copper metabolism and produces a ring of copper in the peripheral cornea (Kayser-Fleischer ring) and a greenish coloured “sunflower cataract” 
*#Atopic dermatitis - Cataract can occur secondary to atopic dermatitis and takes the form of bilateral posterior or anterior stellate opacities. 
*Down’s syndrome - 15% of Down’s have lens opacities severe enough to cause a decrease in acuity (Kanski, 1998) and with a reported prevalence of up to 50% (Scully, 1973).   Secondary to local disease (or complicated cataract) 
*#Anterior uveitis - Anterior uveitis can produce a posterior polar polychromatic cataract. Also, if uveitis not controlled, anterior and posterior subcapsular opacities can progress to complete opacification. 
*#High myopia - Hight myopia can be associated with secondary posterior lens opacities as well as earlier development of nuclear sclerosis. 
*#Glaukomflecken - These are grey-white anterior capsular or subcapsular opacities in pupillary zone pathognomonic with previous attacks of acute angle-closure glaucoma. 
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Revision as of 17:57, 22 February 2018

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Rohan Bir Singh, M.B.B.S.[2]

Overview

Classification

The classification of cataracts is based on four different criteria.

  1. Morphology,
  2. Age of Onset
  3. Maturity
  4. Etiology
  5. Location of opacity
Sub-types
Morphology
  • Capsular
  • Subcapsular
  • Nuclear
  • Corical
  • Lamellar
  • Sutural
  • Capsular 
  1. Congenital capsular thickening- Associated with posterior or anterior polar cataracts and pyramidal cataract. The posterior form may be associated with a hyaloid remnant.
  2. Acquired capsular opacities - Occur with pseudoexfoliation, Infra-red radiation (Glass blower’s cataract) or Secondary to blunt trauma when a Vossius’ ring may be formed. 
  • Subcapsular 
  1. Posterior subcapsular - Lens changes may be associated with secondary or complicated cataracts, drugs e.g., steroids, or be an age-related cataract (Cupuliform). 
  2. Anterior subcapsular  Anterior subcapsular lens changes may be associated with  Wilson’s disease (sunflower cataract) or with drugs e.g., amiodarone
  • Nuclear 
  1. Congenital - Nuclear cataract is that secondary to Rubella 
  2. Age-related - Nuclear sclerosis cataract commonly seen in practice is the age-related form.  
  • Cortical 
  1. Congenital - Congenital cortical cataract is very common and they rarely interfere with vision. e.g., blue dot cataract and coronary cataract.
  2. Age-related - Known as cuneiform cataract that takes the form of “water” clefts and vacuoles. These often appear first in the inferior nasal quadrant of the lens possibly because this is most exposed to UV radiation. 
  • Lamellar 
  1. Congenital - The cataracts are usually congenital and often involve one lamella of the fetal or nuclear zones. Radial, spoke-like opacities (or riders) also often surround the cataract. 
  • Sutural 
  1. These are often known as “Y”-shaped” cataract. 
Maturity
  • Immature Senile Cataract (IMSC) - partially opaque lens, disc view hazy
  • Mature Senile Cataract (MSC) - Completely opaque lens, no disc view
  • Hypermature Senile Cataract (HMSC) - Liquefied cortical matter: Morgagnian Cataract
  • Congenital cataract
Location of opacity
  • Anterior cortical cataract
  • Anterior polar cataract
  • Anterior subcapsular cataract
  • Nuclear cataract
  • Posterior cortical cataract
  • Posterior polar cataract (importance lies in higher risk of complication - posterior capsular tears during surgery)
  • Posterior subcapsular cataract (PSC) (clinically common)
  • Anterior subcapsular lens changes may be associated with Wilson’s disease (sunflower cataract) or with drugs e.g., amiodarone
  • Posterior subcapsular cataract changes may associated with secondary or complicated cataracts, drugs e.g., steroids, or be an age related cataract.
Etiological
  • Congenital 
  • Degenerative or “age related” (senile) 
  • Traumatic 
  • Secondary to other conditions (including metabolic causes) 
  • Toxic 
  • Hereditary 
  • Congenital cataract - Result of heredity (often autosomal dominant), pre-natal infections such as rubella or metabolic disorders. 
    1. Intrauterine infections e.g. Rubella and Toxoplasmosis
    2. Maternal drug ingestion e.g. Thalidomide and corticosteroids. 
    3. Genetically transmitted syndromes 
    4. Microphthalmos
    5. Ocular conditions with associated anomalies e.g. Retinopathy of Prematurity and some types of retinitis pigmentosa. 
    6. Secondary to metabolic disorders e.g. Galactosemia and Wilson’s disease
  • Degenerative or "Age Related" (senile)- Most adults have some degree of opacification of the lens and therefore technically exhibit cataract. 
    1. Subcapsular Anterior subcapsular cataract (directly under the capsule) is associated with fibrous metaplasia of anterior lens epithelium. Posterior subcapsular cataract (cupuliform) lies just in front of posterior capsule and is associated with posterior migration of epithelial cells. 
    2. Cortical Corticalcataract commonly develops as radial or spoke shaped “water-clefts” (cuneiform) togther with vacuoles. Cuneiform changes affect anterior, posterior and equatorial cortex affected.
    3. Nuclear sclerosis  Nuclear cataract is an exacerbation of the normal ageing of lens nucleus and appears as a yellowing of the nucleus. 
  • Traumatic  Trauma is the commonest cause of unilateral cataract in young individuals. Opacities can be the result of various injuries including penetrating injury. Concussion to the eye may cause the iris to be flattened against the lens leaving a Vossius’ ring. 
  • Secondary  Cataract can occur secondary to systemic disease or syndromes including metabolic disorders and due to local disease (ocular).  Many conditions can cause or be associated with cataract 
    1. Diabetes - Diabetes mellitus can cause an exacerbation of the progression of age related degenerative changes. So-called (classical) diabetic cataract occurs during an acute and untreated hyperglycaemic episode and takes the form of cortical “snowflakes”. These occur due to osmotic over-hydration of the lens and can be anterior and/or posterior in position. 
    2. Galactosaemia - This metabolic disease produces an “oil droplet” cataract. 
    3. Wilson’s disease (hepatolenticular degeneration) - This is an anomaly of copper metabolism and produces a ring of copper in the peripheral cornea (Kayser-Fleischer ring) and a greenish coloured “sunflower cataract” 
    4. Atopic dermatitis - Cataract can occur secondary to atopic dermatitis and takes the form of bilateral posterior or anterior stellate opacities. 
  • Down’s syndrome - 15% of Down’s have lens opacities severe enough to cause a decrease in acuity (Kanski, 1998) and with a reported prevalence of up to 50% (Scully, 1973).  Secondary to local disease (or complicated cataract) 
    1. Anterior uveitis - Anterior uveitis can produce a posterior polar polychromatic cataract. Also, if uveitis not controlled, anterior and posterior subcapsular opacities can progress to complete opacification. 
    2. High myopia - Hight myopia can be associated with secondary posterior lens opacities as well as earlier development of nuclear sclerosis. 
    3. Glaukomflecken - These are grey-white anterior capsular or subcapsular opacities in pupillary zone pathognomonic with previous attacks of acute angle-closure glaucoma. 
  • Congenital cataract
  • Sutural cataract
  • Lamellar cataract
  • Zonular cataract
  • Total cataract
  • Secondary cataract
  • 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)
  • 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)
  • 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.

References

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