Question

It has become common to replace the cataract-clouded lens of the eye with an internal lens. This intraocular lens can be chosen so that the person has perfect distant vision. Will the person be able to read without glasses? If the person was nearsighted, is the power of the intraocular lens greater or less than the removed lens?

a. The person will be able to read without glasses; the power of the intraocular lens is greater.
b. The person will be able to read without glasses; the power of the intraocular lens is less.
c. The person will need glasses for reading; the power of the intraocular lens is greater.
d. The person will need glasses for reading; the power of the intraocular lens is less.

Answer 1

If an intraocular lens is selected to give perfect distant vision, the person will need reading glasses, as near vision accommodation is not provided. For a previously nearsighted person, the power of the new intraocular lens will be less than that of the removed lens to correct for the myopia.

Step-by-step explanation:

When an intraocular lens is used to replace a cataract-clouded lens, the main consideration is to restore the person's distant vision. If the lens is adjusted to provide perfect distant vision, the person will typically need glasses for reading because the intraocular lens does not adjust its focal length to accommodate for near vision (which is necessary for activities such as reading). As this accommodation is what’s generally lost with age (a condition known as presbyopia), the provision of a fixed-focus intraocular lens will necessitate the use of reading glasses.

For a person who was nearsighted (myopic), the power of the intraocular lens inserted would be less than that of the removed lens. This is because myopia is corrected by a diverging lens, which has less focusing power than the eye's natural lens when it is causing the myopia.