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How CRT works

The GP lenses for ortho-k are applied at bedtime and worn overnight. While you sleep, the lenses gently reshape the front surface of your eye (the cornea) to correct your vision, so you can see clearly without glasses or contact lenses when you’re awake. The effect is temporary – generally enough to get you through a day or two – so you must wear the reshaping lenses each night to maintain good vision during the day.

Currently, there are two brands of orthokeratology approved by the FDA: Corneal Refractive Therapy (CRT) from Paragon Vision Sciences and Vision Shaping Treatment (VST) from Bausch & Lomb. We recommend CRT to our patients.

DRBRISTOLDr. Bristol answers the most frequent questions he receives about CRT. Click to read.

Who is a candidate for CRT?

CRT is frequently a good option for nearsighted individuals who are too young for LASIK surgery or for some other reason are not good candidates for vision correction surgery. Because it can be discontinued at any time without permanent change to the eye, people of any age can try the procedure, as long as their eyes are healthy.

CRT is particularly appealing for people who participate in sports, or who work in dusty, dirty environments that can make contact lens wear difficult.

What results can you expect from CRT?

The goal for CRT is to correct your vision to 20/20 without eyeglasses or contact lenses during the day. In FDA trials of both CRT and VST lenses, more than 65% of patients were able to achieve 20/20 visual acuity after wearing the reshaping lenses overnight. More than 90% were able to see 20/40 or better (the legal vision requirement for driving without glasses in most states).

Success rates for CRT tend to be higher for mild prescriptions. Call our optometry practice in Bee Caves, TX to find out if your prescription is within the range that can be successfully treated with CRT.

How long does CRT take?

Though you may see some improvement in your vision after a day or two of overnight CRT, it can take several weeks for the full effect to be apparent. During this time, your vision will not be as clear as it was with glasses or contacts, and you are likely to notice some glare and halos around lights. It's possible you may need a temporary pair of eyeglasses for certain tasks, like driving at night, until your vision is fully corrected by the CRT lenses.

Is CRT comfortable?

Some people have comfort issues when attempting to wear gas permeable contact lenses during the day. But since CRT GP lenses are worn during sleep, comfort and lens awareness are generally not a problem.

Cost of CRT

CRT is a significantly longer process than a regular contact lens fitting. It requires a series of office visits and potentially multiple pairs of lenses. Also, GP lenses used for CRT are more costly than most regular contact lenses. Therefore, fees for CRT are higher than fees for regular contact lens fittings.

Can I have LASIK after CRT?

Yes, it's possible to have LASIK surgery after CRT. But because CRT lenses reshape your cornea, you must stop wearing the lenses for a period of time (usually several months) so your eyes can return to their original shape and stabilize. Be sure to tell your LASIK surgeon that you've worn CRT lenses, so they can advise you how long you should wait before having the surgery.

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Model Sanne Vloet on wearing OrthoK/CRTs

Q&A with Dr. Bristol about CRT

Can you please describe to us what CRT is and give us a brief description of how it works?

CRT (Corneal Refractive Therapy) are contact lenses that you sleep in at night, the lenses mold and shape your cornea while you sleep. They flatten it, and by flattening the cornea the right amount, and in the right spot, in the center of the cornea, we can reduce or eliminate nearsightedness. This gives you clear distance vision. You won’t have problems seeing in the distance anymore. Enabling clear vision in the distance without wearing glasses or contacts in the daytime.

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