BC Doctors of Optometry

Orthokeratology (Ortho-K), or Corneal Refractive Therapy (CRT), is an alternative to laser vision correction.

How does orthokeratology work?

Short-sightedness (myopia) is caused by the shape of the eyeball growing too long, or the cornea (clear covering of the eye) curvature becoming too steep.

Glasses and contact lenses work by bending the incoming light properly so that it is precisely focused on the retina at the back of the eye.

Since we cannot shorten the eyeball, laser eye surgery works on the principle of flattening the myopic cornea to correct nearsightedness. CRT also flattens the cornea, but does so without surgery.

CRT is performed by using a highly oxygen permeable contact lens to gently flatten the cornea. It is worn while you sleep and removed while you are awake.

How long does the process take?

For the first 1 to 3 months, the lenses are worn every night while sleeping. Eventually the goal is to reduce the contact lens wear to 2-3 nights a week.

The lenses are not worn while awake. Initially the sharpness of vision will fade towards the end of the day. Once the corneal reshaping has stabilized, your vision will be crisp all day.

What are the risks?

The risks are extremely low. Distorted vision may happen if the contact lenses are not centered properly on the eye. However, your doctor of optometry will perform a thorough fitting process to minimize this occurrence.

Who does CRT work for?

CRT is only effective for people with mild to moderate amounts of nearsightedness and low levels of astigmatism. Your eyes should be free of any eye disease.

Unlike laser eye surgery, CRT is completely reversible. Should you be unhappy with the results at any time, you may discontinue sleeping with the lenses and your original eyeglass prescription will gradually return.

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