Eye glasses and contact lenses

What types of lenses can be used to correct or improve my child’s vision?

There are two types of lenses prescribed for correcting or improving vision:

• Eyeglasses (also called spectacles): Eyeglasses are 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 that 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 lenses are often recommended if there is a large difference in refractive error between the two eyes. (Optically, they function similarly to spectacles.)

What does an eyeglass prescription look like?

For starters, the lens power of your child’s eyeglasses will be measured in diopters, a measurement that reflects the amount of power necessary to focus images directly onto the retina. When looking at an eyeglass prescription, you will see the following abbreviations:

• O.D.: Oculus dextrus simply refers to the right eye. Sometimes the abbreviation R.E. is used.
• O.S.: Oculus sinister refers to the left eye. Sometimes the abbreviation L.E. is used.

In addition, the eyeglass prescription may 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.
• axis: This number measurement describes the astigmatism in degrees from the horizontal axis.

What are the different types of eyeglass lenses?

The type of lenses used in eyeglasses depends on the type of vision problem and may include:

• Concave lenses: These lenses are thinnest in the center and are used to correct nearsightedness (myopia); the numerical prescription in diopters is always marked with a minus (-) symbol.
• Convex lenses: These lenses are thickest in the center, like a magnifying glass, and are used to correct farsightedness (hyperopia); the numerical prescription in diopters is always marked with a plus (+) symbol.
• Cylindrical lenses: These lenses curve more in one direction than in the other and are often used to correct astigmatism.

Which glasses will be best for my child?

If your child is old enough, let him or her play an active role in choosing his or her own glasses. Here are some features to consider:

• shatterproof and impact resistant lenses (such as 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), which are recommended in children under 4

What about contact lenses?

About 24 million Americans wear contact lenses; of those, 80 percent wear daily-wear soft lenses.

There are four types of contact lenses:

• the soft, water-absorbing lens
• the rigid, gas-permeable lens
• other rigid lenses
• other flexible, non-water-absorbing lenses

How do I read a contact lens prescription?

A prescription for contact lenses contains more information than an eyeglass prescription. Special measurements are taken of the curvature of the eye. In addition, your child's physician will determine whether your child’s eyes are too dry for contact lenses, and whether there are any corneal problems that may prevent your child from wearing contact lenses.

Trial lenses are usually tested on the eyes for a period of time to ensure proper fit.

A contact lens prescription usually includes the following information:

• contact lens power (measured in diopters, like eyeglasses)
• contact lens base curve
• diameter of the lens
• name of contact lenses recommended

Unlike eyeglass prescriptions, eye care specialists aren’t 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.