2. Learning objective
• Normal anatomy of lens
• Pathology of cataract formation
• Pathogenesis of radiation induced cataract
3.
4.
5. • Human lens is a clear structure
• Human lens has 2 major regions: Cortical and
nuclear regions.
• Epithelium is seen only in the anterior part of
lens as shown in the picture.
• Lens fibres are produced by this epithelial
cells.
• These cells will migrate from the equator
region towards the centre.
6. • They are devoid of blood supply.
• They depend on the nutrient supply from the
aqueous humour.
• Lens fibre when they loose their capacity to
utilize the nutrient supply or fail to remove
the metabolic products, they get opacified.
• This opacification is called cataract.
7.
8. Pathogenesis of radiation
cataractogenesis
• Radiation will cause damage to epithelial cells.
• Due to this the produced lens fibres from the
capsular epithelial cells will be defective.
• These defective fibres will migrate into the
posterior sub capsular region resulting in
posterior sub capsular cataract.
• Initial stages they are seen as small dots, later
they coalesce to form larger cataract.
9. • There will be a latent period between the
radiation exposure and point of the clinically
significant cataract.
• Severity of cataract depends on number of
capsular cells damaged.
• Capsular cell damage depends on the
absorbed dose.
• Densely ionising radiation produces more
potential cataract.
10.
11. • Severity increases with increase radiation dose.
• There is a threshold below which there is no
disabling cataract will happen.
• So radiation cataractogenesis is a deterministic
effect.
• Threshold dose is 0.5 Gy.
• Annual limit is 20mSv. On a average of 5 years, no
single year exposure should be more than 50
mSv.
12. Conclusion
• Cataractogenesis is a tissue reaction
• Threshold dose is 0.5 Gy.
• It happens due to damage of capsular
epithelial cells.
• These damaged epithelial cells produce
defective lens fibres, these gets accumulated
and opacified.
• Annual limit of radiation exposure is 20 mSv.
