Refractive Errors

An eye with no refractive error
The eye focuses the light using two lenses, the cornea and the “lens”

Refractive Errors: Why do we need to wear glasses or contact lenses?

In ordinary 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, strain free vision. Sometimes this system fails and light rays focus the image ahead or behind the retina. This results in unclear vision, eye strain and headaches. These conditions are known as refractive errors and can be solved by wearing glasses or contact lenses to refocus the light on the retina. Refractive Errors can be of the following types:

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.

Refractive Errors of the Eyes
When the light does not focus on the retina, the eye is said to have a refractive error

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. Some people who are farsighted are able to use their focusing muscle (accommodation) to bring the image forward allowing them to see clearly. This ability worsens with age and reading glasses or bifocals may be needed. 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 presbyopia.

Presbyopia is a normal aging process. As we get older, the lens loses its ability to flex and focus at near objects. 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. Presbyopia is an important concept to understand, if you are over 40, and if you are considering laser correction. One advantage of mild nearsightedness (myopia) is the ability to remove your glasses after presbyopia sets in and still be able to read. If you have Laser Vision Correction for nearsightedness, you will lose this ability. That’s because your vision typically becomes normal, and normal for the aging eye usually will require reading glasses for small print. 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.

Many patients with myopia or hyperopia have some degree of astigmatism. This means that your eye is slightly oval and your cornea is shaped like a football 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.

What can you do about refractive errors, especially if you don’t want to wear glasses or contact lenses? Here we present Solutions to Refractive Errors

Leave a Reply