A myopic person has been using spectacles of | vedclass

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(B) Initially,the person suffered from myopia (nearsightedness),which was corrected by a concave lens of power $-1.00\, D$. This lens allowed him to s

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He developed presbyopia.

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(B) Initially,the person suffered from myopia (nearsightedness),which was corrected by a concave lens of power $-1.00\, D$. This lens allowed him to see distant objects clearly.As the person aged,he developed presbyopia,a condition where the eye loses its ability to focus on near objects due to the weakening of ciliary muscles and reduced flexibility of the eye lens.To correct this,he requires a convex lens for reading. The power of $+2.00\, D$ indicates that his near point has shifted further away from the normal $25\, cm$. Using the lens formula $\frac{1}{f} = \frac{1}{v} - \frac{1}{u}$,where $f = +0.5\, m$ $(+50\, cm)$ and $u = -25\, cm$ (the standard near point),we find the image distance $v$ that his eye can currently accommodate:$\frac{1}{v} = \frac{1}{50} + \frac{1}{-25} = \frac{1-2}{50} = -\frac{1}{50}$.Thus,$v = -50\, cm$. This means his new near point has shifted to $50\, cm$ from his eyes,necessitating the use of reading glasses.

$A$ myopic person has been using spectacles of power $-1.00\, D$ for clear vision. During old age,he also needs to use separate reading glasses of power $+2.00\, D$. Explain what may have happened to his eyesight?

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