The glasses do not correct near or farsightedness. They simply "...redirect light to the inside of the right eye which receives deficient light energy resulting from facial asymmetry that is found to be common in people who have symptoms of dyslexia."
Per his website, Read Fluent, it generally takes 10 - 12 weeks to see a measurable improvement in elementary students reading ability. The site also explains that the person will know within 30 minutes if the RAD Prism glasses are improving their ability to "perceive the written word correctly and consistently."
The theory behind the glasses is the belief that a dyslexic persons eyes are not the same distance from the center of their face. The right eye is believed to always be farther from the center. Therefore, the glasses have a prism in the right lens to make up for the distance. The lens in the left lens is clear plastic.
In an effort to "asses the nature and degree of effectiveness" of the RAD Prism, Dyslexia Solutions Inc., a non-profit company, is conducting a study. The cost to participate ranges from $198 - $288. To learn more about the study go here. You may download the participation application here.
If the following video does not answer all or most of your questions, you can visit Dyslexia Solutions, Inc. frequently asked questions page.