Myopia progression can happen for a few reasons. Usually it occurs because the eye grows too long and light is not focussed correctly onto the retina. Orthok contact lenses are placed on the cornea at the front of the eye overnight and they change the shape of the front surface of the cornea. This allows light to be focussed correctly onto the retina after the lenses are removed, giving clear unaided vision during the day.

New research indicates that one of the causes for the progression of shortsightedness is peripheral retinal blur. This new theory states that while glasses and daytime contact lenses focus the central vision, they do not focus the peripheral vision very well. While the visual system is still developing (up to age in early 20s), the eye grows to try to improve focussing. The amount of growth of the eye is determined by the clarity perceived in the peripheral retina. With glasses the peripheral retina is blurred, since only the central retina is focussed correctly. This results in excessive growth of the eye and further progression of shortsightedness in people prone to this.

Ortho-K lenses reshape the front surface of the eye to form the correct shape for clear focussing onto both the peripheral and the central retina. Glasses and normal contact lenses cannot do this. For this reason it is believed that the progression of shortsightedness is slowed by using orthokeratology.

Can Orthokeratology Make a Long-Term Difference to Children's Vision?

It has been shown that myopia progression can be slowed by performing ortho-k during the ages when progression is occuring. After ceasing Ortho-K, myopia will return. However, the accepted evidence is that the level of myopia progression will be lower in children who have had ortho-k than in children who did not have ortho-k. Ortho-K is a method to try to slow myopia progression in children.
After ceasing Ortho-K, myopia may continue to progress at a normal rate for the age and the person.

Our aim would be to wear ortho-k lenses until an age when myopia progression has become slow or insignificant. Some people may continue ortho-k after this as a means of vision correction.

Is Ortho-k like braces for the eyes?

Orthokeratology is sometimes referred to as braces for the eyes. This is partially correct as the lenses do change the surface shape of the front of the eye. However, the change with orthodontic braces for teeth is permanent, whereas it is reversible with ortho-k. Ortho-K mainly redistributes the corneal epithelial cells on the surface of the cornea, leaving the cornea beneath the epithelium unchanged.

Is OrthoK like wearing tight shoes?

Practitioners who do not perform ortho-k sometimes give the incorrect analogy that the slowing of myopia progression with ortho-k is like wearing tight shoes to stop the feet from growing. This is incorrect as lenses placed at the front of the eye cannot physically stop the whole eye from growing longer.