Eye Care

Correcting or Improving Vision Problems

Lenses for correcting or improving vision:

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

eyeglasses (also called spectacles)
Eyeglasses, the most common form of eyewear used to correct or improve nearly all types of vision problems, are a frame that holds two pieces of glass or plastic, which have been ground into lenses to correct refractive errors. Eyeglasses perform this function by adding or subtracting focusing power to your cornea and lens. Measured in diopters, this measurement (also known as your eyeglass prescription) reflects the amount of power necessary to focus images directly on to the retina.

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 eye wear.

contact lenses
Contact lenses, which are worn directly on the cornea of the eye, are available for the correction of nearly all vision problems. Like eyeglasses, contact lenses help to correct refractive errors and perform this function by adding or subtracting focusing power to your cornea and lens. Measured in diopters, this measurement (also known as your contact lens prescription) reflects the amount of power necessary to focus images directly on to the retina. However, unlike eyeglass prescriptions, by federal law, eye care specialists are not required to give you a copy of your contact lens specifications. However, many eye care specialists will give you a copy if you request one.

Currently, there are five types of contact lenses in use:

the original "hard" lens

the soft, water-absorbing lens

the rigid gas permeable lens

other rigid lenses

other flexible, non-water absorbing lenses

About 24 million Americans wear contact lenses, with soft lenses accounting for 85 percent.

Surgery for correcting or improving vision:

There are several types of surgery available for correcting or improving vision. With several of these procedures, the goal of treatment is to reduce or eliminate an individual's dependence on the use of eyeglasses or contact lens. Corrective surgical procedures include:

radial keratotomy (RK)
This is a surgical procedure to improve myopia (nearsightedness), in which microscopic, radial incisions (keratotomies) are made in the cornea to change the curvature of the cornea over the pupil, thus correcting light refraction.

astigmatic keratotomy (AK)
This procedure is often performed to reduce astigmatism (a condition in which the cornea is not symmetrical). Unlike the radial keratotomy, the incisions involved in AK are made in a curved, rather than radial, pattern.

automated lamellar keratoplasty (ALK)
This surgical procedure has been shown to be effective in reducing high levels of myopia and hyperopia (farsightedness) by slicing across the cornea at different levels (depending upon which condition is being treated) with an instrument called a microkeratome (surgical knife).

photorefractive keratectomy (PRK)
This is a procedure in which an excimer laser is used to reshape the cornea to improve or correct mild to moderate myopia.

laser in-situ keratomileusis (LASIK)
This is a procedure in which a surgical plane (keratome) and an ultraviolet laser are used to remove a thin layer of tissue from the center of the cornea, thus reshaping the cornea and correcting or reducing moderate to high levels of myopia. This procedure is still being tested in clinical trials and is not yet approved by the US Food and Drug Administration (FDA).

This page was last updated on: February 25, 2008.

For more information or to schedule an appointment, please call 410-328-6533.