Corneal Refractive Therapy (CRT)

Wouldn't it be great if your vision could be corrected while you were sleeping? If you answered yes, then please read on. Nearsighted patients can now greatly reduce their dependence on glasses, or eliminate the need to wear them altogether...without surgery! This new development in vision care, approved by the FDA in June 2002, is called Corneal Refractive Therapy, or CRT.

Myopia and its correction

Nearsightedness (myopia) is caused by a mismatch between the optical elements of the eye and the length of the eye. When the eye's optical elements (cornea and lens) are of the ideal strength, they focus light from distant objects precisely on the inside back of the eye (called the retina.) This results in the clearest vision. In myopia, the optical elements of the eye are too strong and focus light from distant objects in front of the retina, resulting in blurry vision.

Normally, correction of myopia involves reducing the overall focusing power of the eye's optical elements by introducing a "minus" lens in front of the eye. If you are nearsighted, your prescription contains negative numbers (-2.50 D.S., -2.00-1.00x180, etc.) These negative numbers indicate the minus lenses needed to cause light to focus precisely on your retina and give you the clearest vision.

Corneal reshaping

While both the internal lens of the eye and the external cornea determine the eye's overall light focusing strength, the cornea is by far the more powerful of the two. The curvature of the cornea is largely what determines how strongly it focuses light. The more curved the cornea is, the more focusing power it has. Through corneal reshaping, the curvature of the cornea can be reduced. Reducing the corneal curvature has the same effect as introducing a minus lens in front of the eye.

The CRT procedure

The cornea is very elastic and can be molded easily. Patients insert the specially designed CRT lenses when they go to bed. During the night, the lenses gently reduce the curvature of their corneas. In the morning, the CRT lenses are removed. Since the corneal curvature has been temporarily reduced, the amount of nearsightedness present has been reduced as well. For many people, vision is improved enough that glasses will not be needed during the day.

CRT is for people of any age who are nearsighted - even children and teenagers. The FDA has approved CRT for people with up to six diopters of myopia (-6.00 as the first number in your prescription); CRT is also approved for use with up to -1.75 diopters of astigmatism.