In pseudophakic eye, which of the following rays penetrate upto retina?
Correct Answer: UV-A
Description: Ans. A. UV-A. (Ref Recent advances in ophthalmology/ Issue 7. Pg. 123)Cornea and lens at its ages provide effective filters for UV radiation. However, UVA radiation can penetrate to the retina in pseudophakic individuals.Increase in UV exposure is asso with increased risk for cataracts, corneal photokeratitis ("snow blindness"), climate droplet keratopathy, retinal damage (in aphakic individuals) and melanoma of the uveal tract. Ultraviolet rays are shorter in wavelength with a higher frequency than light. The mature ocular lens is a very effective filter for 320 to 400 nm radiation in most mammals (including man) there can be no photobinding of lens proteins and photo- chemotherapeutic drugs like 8-MOP.Most people do not see UV light because the lens absorbs UV. In aphakic patients, "near" UV light (300 - 400 nm) can reach visual receptors. Pseudophakia refers to an ocular state in which the natural lens has been replaced with an implanted lens. Apart from the obvious problem of anisometropia, in pseudophakia there is increased risk of retinal exposure to UV light (esp UVA). The natural lens absorbs damaging UV rays, particularly between 300-400 nm and the retina is thus shielded from the potentially damaging radiations.
Category:
Ophthalmology
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