Studies on Vision Therapy for Strabismus
Under optimal clinical conditions the success rate for vision therapy treatment of strabismus is 87%
Vision therapy has been used to successfully treat the various forms of strabismus for over 100 years. Numerous studies have found it to have a 75% success rate in achieving normal cosmetic alignment of the eyes as well as functional binocular vision. Under optimal clinical conditions such as those in a private practice optometric clinic where each patients receives individualized, one-on-one care, the success rate can be as high as 87%.
The Ludlam Study
Dr. William Ludlam conducted a landmark study, but not the first such study, of 149 strabismus patients who came for treatment at the optometric Centre of New York. Ludlam summarized the results as follows:
... combining the functional and almost cured groups and adding four patients whose eyes ware straight ... but are listed as 'moderately improved' because of the the technical requirements of the 'cured' categories (2 subnormal ranges of motor fusion, 1 with a 7" N.P.C. rather than the required 4", and 1 with frequent asthenopia, headaches and accommodative spasm), we may state that a total of 113 (76%) of the patients in the sample had binocular vision with straight eyes 95% of the time or more at dismissal from the regular clinic training sessions. The other 36 patients had residual deviations occurring more often than 5% of the time, and were classified as orthoptic failures. Of these, 8 of the "moderate improvement" group dropped out when quite near the "almost cured" category, i.e. with their eyes straight well over half the time and possessing all of the technical factors necessary for a cure with several moths of additional stabilization work.
Even though the Ludlam study produced outstanding results, Ludlam pointed out that the patients treated at the optometric Centre were treated in poor clinical conditions. For example, they received group therapy, control and management of each case was relatively poor, and they were treated by different clinicians who had different personalities and treatment approaches. He expected that under the optimal conditions of a private practice optometric office, the results would be even better. Indeed, subsequent studies shown this to be the case.
The Hoffman & Allen Study
Another significant study addressed Ludlam's expectation that optimal clinical conditions would produce better results. The study, by Hoffman, Cohen, et al., found that the vision therapy treatment of strabismus had an 87% success rate in clinical circumstances that were "near optimal" such as those conditions that obtain at a private practice optometric clinic.
The researchers also found that younger patients were easier to treat than older ones and that exotropes (patients whose eye turns outwards towards the wall) were easier to treat than esotropes (patients whose eye turns inwards towards to nose) . Even so, the vision therapy treatment of esotropes achieved a very impressive success rate of 74.5%.
The maximum success rate of 100% was obtained in treating intermittent and periodic eye turns whereas constant eye turns were treated at a still-impressive success rate of 76%.
Numerous case reports have been published documenting the treatment of strabismus patients with vision therapy. The most recent was published in August 2011 in the journal Optometry by Peddle and Steiner who discussed two cases of adults with moderate sized intermittent exotropia (eyes turned outward to the wall). Both patients also had asthenopia (eye fatigue and discomfort), headaches, and/or diplopia (double vision). Twenty to 30 in-office VT sessions were recommended to reduce the magnitude and frequency of the deviation as well as improve their binocularity and decrease their symptoms. After completing VT, both patients became phoric for all distances, had normal vergence ability, and had normal near points of convergence.
The history of vision therapy treatment of strabismus
Dr. Susan Barry published an editorial in 2010 in the Journal of the American Optometric Association where she addressed the history of the treatment of strabismus to illustrate the reason why many ophthalmologists recommend surgery only to correct problems like strabismus, which have been effectively treated with vision therapy for decades. Dr. Barry herself underwent 3 strabismus surgeries as a child which failed to give her 3D vision (since birth she was unable to see in three dimensions). She saw an optometrist in her at age 47 who treated her with vision therapy and allowed her to see in 3D for the first time in her life. She wrote the book Fixing my Gaze and was the subject of a New Yorker article by the famous neuro scientist Dr. Oliver Sacks. The following is an excerpt from Dr. Barry's editorial:
Armed with the concept of the critical period, ophthalmologists began to operate on strabismic infants in the first year of life with some success. With the push for early surgery and an emphasis on treating very young children, they abandoned, for the most part, the orthoptic [eye training exercises] techniques pioneered in the late 1800s by Louis Emile Javal. These procedures had been effective in straightening the eyes and promoting stereopsis in adult patients, but the time and effort involved in this training was considered prohibitive. It was left to a small group of optometrists to develop better rehabilitation techniques.
Frederick Brock and William Ludlam as well as other optometrists spent their careers examining not only how their strabismic patients moved their eyes but what it was that their patients actually saw. They realized that strabismus is as much an adaptation to underlying binocular imbalances as it is a cause of a poor ability to fuse. With these observations, they modified and expanded orthoptics into a series of vision training or vision therapy procedures that were enormously effective. In one study of 149 adult strabismics, Ludlam reported that straight eyes and binocular vision developed in 75% of patients, none of whom had had surgery. From the 1930's through the 1950's Brock published extensively in optometric journals. However, with the growing momentum for the concept of the critical period and the push for early strabismic surgery, these studies were largely ignored.
Today, a relatively small group of optometrists still practice and continue to perfect optometric vision therapy techniques. ... Yet, it is difficult for a strabismic patient to learn about, much less access, this type of clinician. Many ophthalmologists are hostile to and ignorant of optometric vision therapy and do not recommend, or may actively discourage, their patients from pursuing these treatments. I was indeed lucky enough to consult an optometrist who saw my need for vision therapy and who referred me to an optometric colleague who was skilled in these techniques. Finally, optometric vision therapy may not be covered by medical insurance, creating the impression that the therapy is either dubious or unaffordable. When adult strabismics are told that they are too old to change, that those who provide optometric vision therapy are practicing unproven regimes, that the therapy is not covered by insurance, and that their subnormal vision is good enough, it's no wonder a story like mine is "one in a million". The barriers to better vision for a strabismic patient originate more from old dogma and professional prejudice that from the underlying biological cause
Dr. Susan Barry gave this well-known TED Talk on her experience with vision therpy and strabismus:
For more information on Dr. Susan Barry, read these publications: