Optometric vision therapy (OVT) involves a significant commitment. There is a commitment of time in order to travel back and forth weekly to the optometrist’s office. There is of course a certain expense involved in order to achieve the best outcome. Staff must be trained well in helping to provide this specialty service, and state of the art practices invest in advanced technologies. Not all insurance carriers reimburse the patient for vision therapy. It would therefore be very attractive if a simple pair of glasses could take the place of the commitment required to succeed through vision therapy. After all, who wouldn’t hope that a simple crutch, brace or appliance could substitute for the need to undertake months if not years of physical, occupational or speech therapy? Much as the answer is there is no magic bullet for any other form of therapy, there are no lenses or prisms that can substitute for what can be accomplished through office based optometric vision therapy.
Here is an interesting exchange from the forum Imamother.com. The question posed is:
“I am looking for an eye Dr. that is experienced in treating dyslexia. A couple of pple recommended a top Dr. named Dr. Clyde Alexander from UK. Does anyone have anything to say about him???”
The first comment offered in reply is:
“My DH has prism glasses – AFAIK they aren’t difficult to make. He has had worlds of improvement since he got them about 4 months ago from a local neuro-opthamologist.”
So what do prism glasses look like? In the amount usually prescribed for children who are having developmental or learning problems, or other types of special needs, they look like any other pair of glasses. They can be combined with any prescription lens power, and can incorporate any colored tint or anti-glare lens coating or treatment. The most common use of prism is base-in reading glasses for convergence insufficiency (CI). Is there any research about the effectiveness of these glasses? Absolutely, and it does not support the magic bullet theory. In 2005 the CITT Investigator group completed a randomized clinical trial comparing the effectiveness of base-in prism reading glasses and placebo reading glasses. The results, published in the British Journal of Ophthalmology, showed that the base-in prism glasses were no more effective than placebo glasses. Their conclusion was that base-in prism reading glasses is not an effective treatment for children with symptomatic CI.
The image above, from the site HowStuffWorks, helps demonstrate what lenses and prisms do. Every prism has a thin part called the apex, and a thick part called the base. Prisms shift the visual space in the direction of its apex or away from its base. It’s good to keep in mind that every lens prescription has prism properties in it, depending on which part of the lens you’re looking through. For a minus lens, used to provide clarity to those who are nearsighted, the thick part or base is at the outer edge. For a plus lens, used to ease focusing effort for those who are relatively farsighted, the thick part of base is at the center of the lens.
Let’s return to the comments from Imamother.com. If a parent obtains a pair of prism glasses and they provide a world of improvement, that is wonderful. I’m all in favor of any intervention that can provide help to children with visual dyslexia, or with any special needs for that matter. In many cases a lens or prism prescription can be a very good adjunct or complement to making changes through vision therapy. A lens or prism prescription can be a valuable tool that helps a patient internalize changes made through vision therapy. In some instances a lens or prism prescription is used to help maintain gains through therapy, guiding growth and development almost like a retainer used after a child has had braces. The key point here is that no “special pair of glasses” incorporating lenses, prisms or tints has ever proven to be an effective substitute for office-based optometric vision therapy.