There are two types of lenses prescribed for correcting or improving vision. These include:
The lens power of eyeglasses is measured in diopters. This measurement reflects the amount of power necessary to focus images directly on to the retina. When looking at an eyeglasses prescription, you will see the following abbreviations:
O.D. Oculus dextrous simply refers to the right eye (sometimes the abbreviation RE is used).
O.S. Oculus sinister refers to the left eye (sometimes the abbreviation LE is used).
In addition, the eyeglass prescription may also contain the following measurements.
|Sphere||This number measurement reflects the extent of the nearsightedness or farsightedness.|
|Cylinder||This number measurement refers to the amount of astigmatism (an irregularly shaped cornea which causes blurring) in the eye.|
|Axis||This number measurement describes the astigmatism in degrees from the horizontal (most left and right eyes have the same axis in astigmatism) axis.|
Bifocal prescriptions, which correct both nearsightedness and farsightedness, usually have an additional measurement listed on the prescription as "add" to indicate the strength of the lens.
By federal law, an eye doctor is required to provide an eyeglass prescription, following an eye exam, at no extra cost. In addition, under federal law, you have the right to a copy of your eyeglass prescription, so that you can shop for the best value in eyewear.
The type of lenses used in eyeglasses depends on the type of vision problem and may include:
Over 30 million Americans wear contact lenses, 80 percent of whom wear daily wear soft lenses. Currently, there are four types of contact lenses in use:
The prescription for contact lenses includes more information than what is available on the prescription for eyeglasses. Special measurements will need to be taken of the curvature of the eye. In addition, the doctor will determine if the eyes are too dry for contact lenses, and if there are any corneal problems that may prevent a person from wearing contact lenses. Trial lenses are usually tested on the eyes for a period of time to ensure proper fit.
The contact lens prescription usually includes the following information:
Eye care specialists are required by federal law to give you a copy of your contact lens specifications.
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