Aetiopathogenesis of cataract

cataract

1. Aetiopathogenesis of Cataract Rahna 66

2. ‘CATARACTA’(LATIN)MEANING ‘WATERFALL’

3. D efinition Any opacity in the lens or its capsule whether developmental or acquired is called a cataract

4. Risk Factors Advancing age ( semipermeabilty ;inactive insoluble proteins ; antioxidative mechanisms) Sunlight Radiant energy Mechanical trauma Vitamins A,C,E deficiency Diabetes ( sugars – glycation) Smoking ( cyanate from cigarette smoke – carbamylation ) Hypocalcaemia Miotics Corticosteroids Toxic substances – naphthalene , dinitrophenol ,iron, copper Genetic

5. Pathomechanism Hydration Due to osmotic changes or change in semipermeability in capsule Actual droplets of fluid gather under capsule forming lacunae between fibres The entire tissue swells ( intumescence) and become opaque Reversible to some extent ( Juvenile insulin dependent diabetics lens become clearer after control of hyperglycaemia) Denaturation of lens proteins Irreversible Seen in young lens or cortex of adult lens Slow sclerosis older and inactive fibres of nucleus

6. Oxidative damage to membrane and proteins Formation of aberrant lens fibres Posterior subcapsular cataract ; germinal epithelium loses ability to form normal fibres Opacification of lens epithelium Acute angle closure glaucoma ; epithelial cell necrosis leads to focal opacification of lens epithelium

7. Opacification of lens fibres with fibrous metaplasia Complicated cataract Failure of ion pumps Increased intralenticular Ca and Na with decrease in K Deposition of abnormal products of metabolism ,drugs or metals in storage diseases ( Fabry ) ,metabolic (Wilson), and toxic reactions ( siderosis )

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