How does Ortho-K work for myopia control?
It generally works very well. Of all the optical solutions that have been studied in controlled clinical trials, Ortho-K has been shown to slow myopic progression the most. It is thought that the control occurs due to the lenses creating what is called peripheral myopia. Peripheral myopia is thought to be a significant part of the mechanism that controls the process of emmetropization, which is how the eye determines to stop its growth and myopic progression. An eye with peripheral myopia will generally not become more myopic so that the artificial creation of peripheral myopia by use of optical devices is important in several myopia prevention techniques.
Clinical trials have reported slowing myopia 55% to 100%. Retrospective case studies, a less stringent study design, have show high rates of prevention. The following chart is from a study by Wilcox and Bartels.
The blue line represents those patients not wearing Ortho-K lenses whose myopia progressed (the line slopes upward) and the red line represents those patients wearing Ortho-K lenses whose myopia was stabilized.
The results of the study showed:
- The mean change in spherical equivalent refractive error (SEQ) during the No-mold phase was -0.37D per year.
- The mean change in SEQ during the molded/Unmolded phase was -.03 D per year.
Lets look at how that works out. Lets see about a 9 year old patient named “Jimmie”.
Jimmie sees the eye doctor at age 9, and lets say for arguments sake we knew he was beginning myopia. Lets compare what would happen if, based on the above research, Jimmie started OrthoK (red lines) and if he did not (blue lines). Charts based on above results, and projected for 7 years.
The above chart shows how Jimmie’s prescription would progress according to Drs. Wilcox and Bartels research.Its important to note that most patients start wearing their glasses for most daytime activities, except reading / computer, at -1.00 Diopters (Green Line), and virtually all activities at -2.50 Diopters (Purple Line), including reading / computer.
By the way, at about -1.00 Diopters, you cannot pass your drivers test without glasses any longer.Jimmie sure won’t at -2.59 Diopters.
How does Diopters in the prescription relate to Uncorrect Vision Range (UCVR) in feet? Its calculated like this:
1 X 3.2808 = UCVR in Feet
Diopters in RX
In the chart below, you can see Jimmie retains a much larger degree of UCVR in the OrthoK scenario, which makes sense since his prescription is barely changing. By age 16, Jimmie with OrthoK still doesn’t need a daytime prescription for anything. Jimmie without OrthoK is living in glasses for everything.
You can see all the current research on OrthoKeratology as it relates to Myopia Control at Myopia Prevention and Control.