Corneal reshaping (orthokeratology) has proven successful among patients as a visual aid and for myopia control. Research indicates it may be the images that focus on the peripheral retina that control the ultimate growth of the eye. This suggests that myopia may be controlled in young children by manipulating the peripheral optics of the eye.
The mechanism for this effect appears related to post-ortho k corneal shape. It is flatter in the center and gradually steepens across the pupil. It's been well documented that myopic eyes have significant hyperopic defocus in the area of the peripheral retina. In this situation the central rays of light come to focus on the fovea while the peripheral rays of light fall posterior to the retina, allowing the eye to grow more myopic. After ortho k the cornea generates a negative curvature field where the peripheral rays of light are focused anterior to the retina, creating the environment for a myopia control effect.
Three years ago a -3.25 DS 9 year old patient with progressive myopia since age 6, was placed into CRT lenses for overnight ortho k. At his last examination, his VA without correction was 20/20 in both eyes. Of greatest interest was that he has required no change in the base curve radius of his lenses, implying that his axial length or myopia has not increased.