The normal eye, myopic eye and old age As we age, the lens of the eye hardens and accommodation no longer occurs: it is presbyopia.
Paradoxically, with age, a nearsighted person sees better than a "normal" person.
The aim of this exercise is to explain this paradox. The eye is modeled by a constant focal
length f′0 when the eye is presbyopic and by a screen (the retina) at the distance d from the
lens (d = 15 mm).
1. A normal, presbyopic eye sees an object at infinity in focus while a myopic eye sees an
object at a distance Dm from the eye (Dm = 15 cm).
What relation do we have in the two cases between f′0 and d?
2. A presbyopic person reads a newspaper placed 25 cm from his/her eyes. The radius r0 of
the pupil of the eye is 1 mm. Calculate the diameter of the spot on the retina image from a
log point, for a myopic eye and a normal eye. Conclude