These are conditions which require glasses or contact lenses to see clearly because the cornea of your eye is shaped differently than an eye without a refractive disorder. In nearsighted patients, the cornea is too steep for the length of the eye, which usually makes it difficult to see in the distance. Astigmatism is caused by an irregularly shaped cornea, producing blurring, and glare.
Like a camera, the human eye must be properly focused to see an image clearly. If light does not bend or refract correctly, and focus directly on the retina, the result is blurred vision, or a refractive error.
The retina functions like the film of the camera and sends signals back to your brain which are interpreted as vision. The cornea is responsible for 75% of the focusing power of your eye. The lens within your eye performs the fine focusing of the light onto your retina. If the focusing process works perfectly, all of the light rays meet at a single point. A sharp image of the object you are looking at will then be focused onto the retina and you will see this image clearly. However, if the light is focused in front of or behind the retina, the image on the retina will be blurred and you are said to have a refractive error. Refractive errors are not diseases, but are normal conditions of the eye.
The main type of Refractive Errors are:
Glasses, contact lenses or one of the currently available refractive surgical procedures can usually correct all of these refractive errors. Glasses or contact lenses are the most acceptable options for most people.
How are refractive errors corrected?
Eyeglasses or contact lenses are the most common methods of correcting refractive errors. They work by refocusing light rays on the retina, compensating for the shape of your eye. Refractive surgery is also an option to correct or improve your vision. These surgical procedures are used to adjust your eye's focusing ability by reshaping the cornea, or front surface of your eye. There is not adequate scientific evidence to suggest that eye exercises, vitamins or pills can prevent or cure refractive errors.
Eyeglasses
Glasses are an easy method to correct refractive errors. They also can help protect your eyes from harmful light rays, such as ultraviolet (UV) light rays. A special coating that screens out UV light is available when you order your glasses.
Bifocals are glasses used to correct presbyopia. They have a correction for reading on the bottom half of the lens and another for seeing at a distance on the top. Trifocals are lenses with three different lens corrections in one set of eyeglasses.
If you don't need correction for seeing at a distance, you can receive a prescription for reading glasses or buy them over the counter to correct presbyopia.
No exercise or medication can reverse presbyopia. You will probably need to change your prescription from time to time between the ages of 40 and 60, because your lens will continue to lose flexibility.
Contact Lenses
There are now a wide variety of contact lenses available. The type that is best for you depends on your refractive error and your lifestyle. If you want to wear contact lenses, discuss the various options with your eye care practioner.
You may have heard of a process called orthokeratology to treat myopia. It uses a special type of hard contact lenses to flatten the cornea and reduce the refractive error. Correction of vision from orthokeratology is temporary. If wear of the lenses is discontinued, the cornea returns to its original shape and myopia returns.
