Presbyopia is impairment of vision due to advancing years. As we mature, the cryatlline lens of the eye loses its elasticity and causes the near point of clear vision to be removed farther from the eye. This means you need a different correction for close work than you need for distance vision. This usually occurs in the early or mid-forties.

How will this affect me?
If you do need correction for distance vision, you will notice that you have to hold reading material farther and farther away to see it clearly. Finally you will need reading glasses to magnify the print.

If you are nearsighted, you will notice that you cannot read with your distance correction anymore, and you will find you are taking your glasses off in order to be able to read.

If you are farsighted, you will simply need more magnification in order to be able to read than you need for your distance vision, and will probably start into bifocals rather quickly.

Does it get worse?
The amount of correction needed for close work does increase up to a point, and then seems to stabilize.

What can be done?
Eventually, the lens or cataract will need to be removed. See cataracts.