Cataract classification

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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]

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  Congenital capsular thickening- Associated with posterior or anterior polar cataracts and pyramidal cataract. The posterior form may be associated with a hyaloid remnant. 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  Posterior subcapsular - Lens changes may be associated with secondary or complicated cataracts, drugs e.g., steroids, or be an age-related cataract (Cupuliform).  Anterior subcapsular  Anterior subcapsular lens changes may be associated with  Wilson’s disease (sunflower cataract) or with drugs e.g., amiodarone Nuclear  Congenital - Nuclear cataract is that secondary to Rubella  Age-related - Nuclear sclerosis cataract commonly seen in practice is the age-related form.   Cortical  Congenital - Congenital cortical cataract is very common and they rarely interfere with vision. e.g., blue dot cataract and coronary cataract. 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  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  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	Immature or incomplete - The cataract is present but not visually incapacitating. Surgery may or may not be indicated.  Mature - The whole lens is opaque. Surgery is usually indicated.  Intumescent - The lens is swollen. Surgery is indicated.  Hypermature - The lens is shrunken, yellow and the capsule is wrinkled.  Morganian cataract - A hypermature cataract with liquified cortex and in which the nucleus settles inferiorly.
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), prenatal infections such as rubella or metabolic disorders.  Intrauterine infections e.g. Rubella and Toxoplasmosis.  Maternal drug ingestion e.g. Thalidomide and corticosteroids.  Genetically transmitted syndromes  Microphthalmos 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 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 (cupuliform) lies just in front of the posterior capsule and is associated with posterior migration of epithelial cells.  Cortical cataract commonly develops as radial or spoke-shaped “water-clefts” (cuneiform) together with vacuoles. Cuneiform changes affect anterior, posterior and equatorial cortex affected. Nuclear sclerosis  Nuclear cataract is an exacerbation of the normal aging 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).  Secondary to systemic diseases/metabolic disorders 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 colored “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 the 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.  Toxic  Corticosteroids - Steroids used for prolonged therapy produce a posterior subcapsular cataract.  Amiodarone - Amiodarone can cause anterior capsular changes in up to 50% of patients. The opacities tend to be visually insignificant.