 Eye Glasses and Contact Lenses
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There are two types of lenses prescribed for correcting or improving vision. These include:
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- eyeglasses (also called spectacles) - Eyeglasses, the most common form of eyewear used to correct or improve many types of vision problems including refractive errors. Refractive errors can include nearsightedness or myopia (difficulty seeing far away), farsightedness or hyperopia (difficulty seeing close up), and astigmatism (distorted vision which can affect both distance and near vision). Eyeglasses perform this function by adding or subtracting focusing power to the eye's cornea and lens, thereby creating a clear image.
- contact lenses - Contact lenses are worn directly on the cornea of the eye. Contact lens are often recommended if there is a large difference in refractive error between the two eyes. (Optically, they function similarly to spectacles.)
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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 eyeglass prescription, you will see the following abbreviations:
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- O.D. - Oculus dextrus 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).
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In addition, the eyeglass prescription may also contain the following measurements:
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- sphere - this number measurement reflects the extent of the nearsightedness or farsightedness.
- cylinder - this number measurement refers to the amount of astigmatism.
- axis - this number measurement describes the astigmatism in degrees from the horizontal axis.
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Bifocal prescriptions, which correct both nearsightedness and farsightedness, usually have an additional measurement listed on the prescription as an "add," to indicate the strength of the lens for near.
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The type of lenses used in eyeglasses depends on the type of vision problem, and may include:
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- concave lenses - are thinnest in the center. Used to correct nearsightedness (myopia), the numerical prescription in diopters is always marked with a minus (-) symbol.
- convex lenses - are thickest in the center, like a magnifying glass. Used to correct farsightedness (hyperopia), the numerical prescription in diopters is always marked with a plus (+) symbol.
- cylindrical lenses - curve more in one direction than in the other and are often used to correct astigmatism.
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If old enough, let your child play an active role in choosing his/her own glasses. The following are features to consider when buying eyeglasses for children:
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If old enough, let your child play an active role in choosing his/her own glasses. The following are features to consider when buying eyeglasses for children:
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- shatterproof and impact resistant lenses (i.e. polycarbonate lenses) - especially for children who participate in sport activities
- scratch-resistant coating on the lenses
- spring-loaded frames that are less likely to be bent or warped
- silicone nose pads that prevent glasses from slipping
- cable temples (ear pieces that wrap around the ear) - recommended in children under 4 years.
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About 36 million Americans wear contact lenses, 80 percent of whom wear daily wear soft lenses. Currently, there are four types of contact lenses in use, including the following:
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- the soft, water-absorbing lens
- the rigid, gas-permeable lens
- other rigid lenses
- other flexible, non-water absorbing lenses
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The prescription for contact lenses includes more information than what is available on the prescription for eyeglasses. Special measurements are taken of the curvature of the eye. In addition, your child's physician 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.
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- contact lens power (measured in diopters, like eyeglasses)
- contact lens base curve
- diameter of the lens
- name of contact lenses recommended
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Unlike eyeglass prescriptions, eye care specialists are not required by federal law to give you a copy of your child's contact lens specifications. However, many eye care specialists will give you a copy if you request one.
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