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
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 can be a result of heredity (often autosomal dominant), pre-natal 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 is often associated with cataract. Ocular conditions with associated anomalies e.g. retinopathy of prematurity & some types of retinitis pigmentosa.  Secondary to metabolic disorders  e.g. Galactosemia & Wilson’s disease

• 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.