Presbyopia is age related long-sightedness and is a direct effect of age
It's is thought to be caused by the lens of the eye losing its elasticity which affects its ability to alter its focal length
If you are over 40 it is almost a certainty that you are beginning to suffer the effects of Presbyopia.
Although, there is a theory that it is the muscles that control the lens losing their ability to contract that causes it. Ether way there aint much we can do about preventing it from happening.
But you can deal with it relatively easily
If you are longsighted you can see objects at practically all distances, but can only focus properly at certain distances.
It is sort of like a fixed focus camera in which you cant change the size of the lens aperture, so you cant focus on objects nearer that about six feet. But can take a perfectly good picture of someone 100 feet away
The most noticeable symptoms are a gradual inability to focus when reading, or doing close up work.
To overcome this you tend to hold the work/reading matter further and further away, till you almost get to the stage when your arms aren’t long enough. You may also have difficulty keeping your place when reading. Even to the extent of keeping on the right line.
And the bad news is it will get worse as time goes on
Although no cure exists for Presbyopia short of an Elixir of youth, which would (hopefully) restore the elasticity, and the auto-focusing ability of the eyes.
The good news is …
For people who have otherwise normal vision a simple pair of reading glasses will eliminate the problem
And for those who already have vision problems there are several treatment alternatives...
Vision can be corrected with glasses for distance or reading or a combination of the two using Bi Focal lenses or Vari focal lenses
Contact lenses are available for presbyopes; (makes you sound like a werewolf doesn’t it?) in which one lens is configured for distance, and one for reading. (called Monovision) Which is a sort of improvement; but it can result in problems, due to the loss of binocular vision which we rely on to judge distance. Alternatively,you can now get bifocal and varifocal contact lenses which work in much the same way as bifocal and varifocal glasses.
Laser eye surgery
Lasik Eye surgery is able to produce the same monovision as contact lenses. But the downside of this is that it is permanent, so if you later have problems due to the lack of binocular vision your screwed.