Myopia (near-sightedness) is a condition in which the eyeball itself is either too long, or the front of the eye (the cornea) is too curved, or a combination of both. The result is that light from distant objects is focused in front of the retina (instead of on the retina). This makes doing things like driving and reading far-off signs difficult. Myopia is most often corrected with soft contact lenses or eyeglasses.
Hyperopia (far-sightedness) is a condition in which the eyeball is too short, or the cornea is too curved, or a combination of both. The result is that light from objects is focused behind the retina. We can use some of the focusing power of the natural lens within the eye to help refocus the light, but this can lead to eyestrain or tired eyes, especially when working at near. The focusing ability of the eyes also reduces as we get older, making it more difficult to overcome the focusing problem. Hyperopia is most often corrected with soft contact lenses or eyeglasses.
Presbyopia is the loss of focusing ability of the eyes. The focusing lens inside the eye hardens as we get older, resulting in the closest point that we can focus on moving further and further back until reading small print becomes more and more difficult. This is why many people who have never worn spectacles find that they need a pair of reading spectacles when they reach their mid-forties.Glasses in the form of bifocals, with or without a line, are the most common correction for this condition. There are several contact lens choices now available to correct this for the right patients.
Astigmatism is a condition in which the front of the eye (the cornea) is oval shaped instead of round. 80% of eyes have some form of astigmatism that may or may not need corrected. It is the most common form of eye problem. Some people describe it as having a football ball shaped cornea. You could be near-sighted and have astigmatism or far-sighted and have astigmatism, or just astigmatism by itself. It is most often corrected with soft contact lenses or eyeglasses.