All eyes slowly lose their focusing ability with increasing age. Presbyopia is the name given to this gradual loss of the ability to focus on nearby objects. It's a natural, often annoying part of getting older. It becomes noticeable after the age of 40 years and continues to worsen until around age 65. It is commonly confused with long-sightedness as the symptoms of eye strain, tiredness and difficulty focussing at near are very similar; however, the cause of near vision reduction in presbyopia is progressive and due to ageing rather than the shape or power of the eye.  

The lens inside the eye, that in younger eyes has a wide range of focus, becomes thicker and gradually loses its flexibility. This means it becomes difficult to hold things very close and see clearly. While it can appear to develop suddenly, the actual loss of ability to focus begins in adolescence and gets worse over the following years, so by sometime in our 40s, we become aware of difficulty seeing fine objects or small print; headaches, tired or sore eyes when reading; the need to hold reading material further away; and the need to increase the lighting for close work.  

Presbyopia is easily corrected with reading glasses, extended focus (occupational) glasses, multifocal (a.k.a. progressive) glasses and contact lenses.