Corneal Refractive Therapy (CRT) is the Paragon Vision Sciences trademarked name for their FDA-approved orthokeratology lens system — a type of overnight rigid contact lens designed to temporarily reshape the cornea and provide clear daytime vision without glasses or daytime contacts. CRT lenses are among the most studied and widely used orthokeratology platforms in the United States.

CRT vs. Standard Ortho-K

All CRT lenses are orthokeratology lenses, but not all orthokeratology lenses are CRT — the term specifically refers to lenses manufactured using Paragon's proprietary oxygen-permeable material (Paragon HDS 100) and design geometry. CRT lenses have been FDA-cleared since 2002 for myopia correction up to –6.00 diopters, with modest amounts of astigmatism also addressable in many cases.

The Myopia Control Benefit

CRT and orthokeratology lenses generally have become a cornerstone of myopia management for children and teenagers. Research consistently shows that the peripheral defocus created by overnight corneal reshaping slows the axial elongation of the eye that drives myopia progression. Several peer-reviewed studies report a 30–50% reduction in myopia progression compared to single-vision glasses or soft lenses — making CRT one of the most effective myopia control options available.

What to Expect

  • Custom lenses designed from your corneal topography map
  • Worn only during sleep — 6 to 8 hours per night is ideal
  • Most patients achieve functional vision within the first few nights; full correction in 1–2 weeks
  • Follow-up visits at 1 week, 1 month, and every 6–12 months thereafter
  • Fully reversible — cornea returns to its natural shape if wear is discontinued

CRT is an excellent option for motivated patients seeking a non-surgical, reversible path to daytime visual freedom. Contact us to discuss whether you or your child is a good candidate.