Cataract hereditary and Congenital Topic 35
= development of opacity In the normally transparent crystalline lens
There are different classification
A) According to aetiology (cause)
- 1. Congenital & developmental
- 2. Acquired –Senile, complicated, metabolic, electric, radiational, toxic ,
- Association with skin diseases ,osseous diseases & syndromes
B) Morphology
- 1. Capsular cataract ; either Anterior or posterior capsule
- 2. Subcapsular→ superficial part of the cortex (just below the capsule)
- Also anterior or posterior subscapular cataract
- 3. Cortical: involves major part of cortex
- 4. Supranuclear cataract ( just deeper part of cortex)
- 5. Nuclear cataract (involves the nucleus of lens)
- 6. Polar cataract ( anterior or posterior polar )
Congenital & developmental cataract
=very common in population but usually without visual disturbances
=due to disturbances of growth of the lens before birth or from after birth to adolescence
- If congenital only the embryonic/foetal nucleus is affected but
- Developmental may involve infantile /adult nucleus
- It usually affects the layer that is being formed at that time thus previous or subsequent fibres usually are normal and clear
Aetiology: unknown but some factors
- Heredity : 1/3 of all congenital due to chromosomal dominant patters
- Maternal: malnutrition, infections (rubella) ,drug (corticosteroids, thalidomide) radiation
- Infantile : anoxia, metabolic (Galactosemia, hypoglycaemia) , trauma &malnutrition
- Idiopathic : 50 % unknown
Classified according to morphology
- 1. Capsular ;anterior or posterior pole
- a) Anterior : central part of the anterior capsule &superficial most cortex
Caused by : delayed anterior chamber or corneal perforation (contact between lens &cornea) Types: thickened white plaque in centre of capsule , pyramidal (with apex towards cornea) Reduplicated : thickening of central point and involvement of lens fibres immediately beneath
- b) Posterior :very common ,small circular circumcised opacity in posterior
- Cause: hyaloid artery remnants , lenticonus, hyperplastic primary vitreous
- Types : stationary or progressive (progression after birth)
- 2. Nuclear: cataracta centralis puverulenta → bilateral nuclear powdery opacity in embryonic
- Total nuclear : embryonic,fetal +infantile nuc.→ dense chalky with serious impairment
- 3.Lamellar /zonular :most common type of congenital (40%)
- Congenital or vitamin D deficiency or rubella
- Features : foetal nucleus surrounding embryonic layer
- Bilateral , main mass internal &external to mass is clear
But small linear opacities towards the equator sometimes
- 4.Generalised
- a) Coronary : extremely common of developmental (in puberty)
- Affect adolescent nucleus , many hundreds of opacities in A regular radial distribution in periphery (hence unaffected vision)
- b) Blue dot :present as blue in periphery of adolescent nucleus (2nd decade)