Presbyopia is a normal ageing process of the eye which makes reading and seeing objects up close more difficult, usually from your mid-40s onwards.
In a young person, the natural lens in the eye is able to change its shape to alter focus when viewing distant and near objects. Presbyopia occurs because the lens loses its ability to change focus from distance to near as the lens becomes stiffer and the eye’s focusing muscles become weaker with age.
If you are already wearing glasses for long-sightedness, you will usually need bifocal or multifocal lenses to enable you to see both far and near as presbyopia develops. Short-sighted people will still need their glasses for distance vision, but some may be able to take their glasses off for close work when they become presbyopic.