To understand which laser eye surgery is best, you need to know how your eyes work.
How do the eyes work?
What is Myopia or near-sightedness?
Myopia occurs when the eyeball is too long. As a result, parallel rays of light come into focus in front of the retina. People with myopia can see objects that are closer to them more clearly, but distant objects are blurred. They may, for example, have difficulty seeing detail on the TV screen and will not be able to drive without wearing their glasses. The longer the eyeball is the higher the glasses prescription would be. People who are short-sighted get a concave (minus) lenses on their glasses which diverges the light and help focus it back onto the retina rather than in front of the retina.
What is Long-sightedness or Hyperopia?
Hyperopia (long-sightedness) occurs when the eyeball is short. As a result parallel rays of light come into focus behind the retina when the eye is in an unaccommodated state. In younger people with long-sightedness, the lens is still flexible and is able to change its shape to accommodate and focus the rays of light on to the retina, providing clear vision without glasses. This however exposes the eye to stress due to the need for constant use of the eye muscle (accommodation), sometimes leading to eye fatigue and headaches. As the natural lens stiffens with age, patients with long-sightedness are no longer able to accommodate and become more dependent on glasses or contact lenses. Patients with hyperopia wear convex (plus) lenses which makes the light rays to converge and hence focus on the retina rather than behind it.
What is an Astigmatism?
What is irregular astigmatism?
What is Presbyopia?
This is a normal, age-related condition which typically starts to occur after 40 years of age. It’s the reason most people need reading glasses after this age, even if they have never needed glasses before.
This is because the natural lens of the eye becomes stiffer and loses its flexibility to change its focusing power. In younger patients, the lens is able to increase focussing power (accommodate), to see near objects clearly, and these patients only need glasses for distance. However, presbyopic individuals require bifocals/varifocal glasses or two separate glasses to see near and distance clearly.
Patients who have laser eye surgery may have, or will eventually, develop presbyopia as the normal ageing process.