If you have a visual problem, the first thing to determine is whether the problem is caused by a refractive error, or if there is an underlying medical condition.
Most cases of blurred vision are due to errors of refraction caused by a disturbance in the way light rays are focused within the eye.
Short-sightedness (or Myopia)
Myopia is when people see near objects more clearly, but distant objects are blurry. It occurs when light rays entering the eye are focused in front of the retina instead of directly on it.
Myopia may be a result of the curvature (power) of the cornea being too strong, the crystalline lens changing with age or the length of the eyeball being too long. Myopia is often inherited; it usually starts in childhood and typically stabilizes in the late teens or early adulthood.
Far-sightedness or Hyperopia
Hyperopia, or far-sightedness, is a common vision problem. Hyperopia means you can see distant objects very well, but have difficulty seeing objects that are up close.
Astigmatism
Astigmatism is the result of having a corneal surface that is not regular in shape. The eye is unable to focus clearly at any distance because of this irregular focusing surface.
Individuals with no astigmatism have corneas that are shaped like a soccer ball while individuals with astigmatism have corneas that are shaped more like a football.
Refractive laser surgery is an option for correcting myopia, hyperopia and astigmatism. It may reduce or eliminate your need to wear glasses or contact lenses.
Presbyopia
Patients always present saying “I used to be able to read properly and now I can’t! What is happening to my eyes?”. Presbyopia happens to everyone (usually starting in their mid forties) and it is not something you can prevent. It is the loss of the ability to focus on near objects which results in the need for reading glasses.
Why does it occur?
The natural lens and the muscles controlling its movement lose their ability to change shape which shifts the focus from distant objects to near objects.
It is important to remember that it is not considered to be an eye disease. The process occurs gradually over a number of years.
Presbyopia is treated using either spectacle correction through reading or multifocal lenses.
Refractive lenses exchange can also be used to correct for presbyopia – the insertion of an intraocular lens (IOL) which can be set to allow for clear near vision.