Human Eye

The human eye is in many ways similar to a camera. Just as the camera records images on a film, the eye records them on a special layer called the retina. Like the lenses in the camera focuses the imagesl the eye also has lenses to focus images on the retina. The eye has two lenses: the cornea and the "lens". The cornea is a fixed focus lens. It simply bends light rays by a fixed amount. The lens is like an auto focus system. It changes its shape to focus images perfectly on the retina, so that images appear sharp and crisp.

Sometimes when there is a mismatch between the curvature of the cornea, the power of the lens and the length of the eye, the eye focuses images ahead of or behind the retina. This is known as a refractive error. This results in unclear vision, eyestrain and headaches. To eliminate this mismatch, spectacles or contact lenses need to be worn

Refravtive Error

In normal circumstances, the curvature of the cornea, the power of the lens and the length of the eye are finely coordinated to focus images perfectly on the retina and thereby produce clear vision. Sometimes this system fails and light rays focus the image ahead or behind the retina. This results in unclear vision. These conditions are known as refractive errors and can be of the following types:

Nearsightedness
Technically called myopia, nearsightedness means you have trouble seeing and resolving objects at a distance. When the eye is too long in relation to the curvature of the cornea, images focus in front of the retina instead of on it and objects at distances appear blurred. Patients with myopia are able to see near objects.

Farsightedness
Technically called hyperopia, farsightedness means you have trouble with close up vision. It occurs when the eye is functionally too short. The rays of light are focused behind the retina producing a blurred image. Farsighted people see distance objects more clearly than near objects.

Aging eyes
The normal solution for refractive errors is to wear spectacles or contact lenses to see clearly. There is one other condition for which people normally need to wear glasses. This condition is normally associated with aging, and is known as prebyopia.

Presbyopia is a normal aging process. As we get older, the lens loses its ability to flex and focus at near. The onset of presbyopia typically is between 40 and 50. When this occurs people who already wear glasses may need bifocals and those who have never worn glasses may require reading glasses. The excimer laser has no effect on your focusing muscles and therefore cannot treat presbyopia. However, there are ways around this problem, and it is best to talk to one of our expert eye doctors to discuss the best solution for you.

Astigmatism
Many patients with myopia or hyperopia have some degree of astigmatism. This means that your eye is slightly oval rather than a sphere. People with astigmatism experience distortion or tilting of images due to unequal bending of the rays of light entering your eyes. High degrees of astigmatism will cause blurred vision for distance and near objects.