Presbyopia 

Presbyopia is a vision problem that happens when the lens of the eye becomes less flexible. This makes it very difficult to focus on nearby objects. 

This condition might seem like it happens suddenly; however, the actual changes in the lens happen over years. Usually, sufferers will notice signs of presbyopia in their 40s. It is comforting to note that presbyopia is a natural part of the aging process and not a disease. However, this also means that it can't really be prevented. 

You might notice that you are holding books, menus or reading material further away than usual. Your vision may be blurry when reading at a normal distance, and you may experience eye tiredness or headaches after doing close work.