ULTRAVIOLET RAYS
Ultraviolet rays are invisible rays, sunlight being the principal source of ultraviolet rays.
Types of ultraviolet Rays
Depending upon their absorption spectrum, UV light has been divided into three bands:
1. Ultraviolet A rays
2. Ultraviolet B rays
3. Ultraviolet C rays
1. Ultraviolet A rays:
This band of UV rays is absorbed by crystalline lens and thus retina is protected against their bad effects. Prolonged exposure to these rays causes cataract formation. IOLs implanted during cataract surgery have chromophores [inhibitors of UV rays] to protect retina against UV rays.
2. Ultraviolet B rays:
This band is responsible for snow blindness and photo keratitis caused by welding arc. Prolonged exposure to these rays can cause formation of pinguecula and pterygium.
3. Ultraviolet C rays:
This band is blocked by the ozone layer of atmosphere.