Presbyopia is the loss of close-up focusing. It is not a disease. It is the normal aging process of the eye. When you are younger, the lens in your eye changes shape to focus light directly on the back of your eye (the retina). But as you get older, the lens hardens and can't change its shape as easily. It then can’t focus clearly on close objects. This makes them look blurry.
Presbyopia makes it hard to do things close up. This includes reading small print, using tools, or threading a needle. The first sign may be a tired feeling when you look at something close up. Presbyopia most often starts when you’re 40 to 45 years old.