Mr. Sharma is a 76 year old man. His vision was gradually becoming blurred. He consulted an eye doctor and it was diagnosed as cataract.
Why does the vision become blurred?
Topic: Cataract — cause of blurring
Answer
Because the clouded, opaque lens can no longer transmit light freely. Light entering the eye is SCATTERED and ABSORBED instead of being focused sharply, so a clear image is not formed on the retina and vision becomes hazy and dim.
The reasoning must connect the OPACITY to the failure to FOCUS ON THE RETINA. An answer saying only "because the lens is damaged" does not explain anything.
Two effects follow from a cloudy lens: less light gets through (so vision dims) and what does get through is scattered in all directions (so the image blurs instead of forming a sharp point on the retina).
NOTE THE DIFFERENCE from myopia, hypermetropia and presbyopia. In those the lens is CLEAR but focuses in the wrong PLACE, so a spectacle lens corrects them. In cataract the lens is not transparent at all, so no spectacles can help — only surgery. That is why the question is worth asking.