Orthoptics aims to treat binocular vision disorders such as strabismus, and diplopia. It is practiced by optometrists and ophthalmologists, as well as orthoptists and occupational therapists under the guidance of some ophthalmologists and pediatric ophthalmologists.
Behavioral vision therapy is practiced primarily by optometrists who specialize in this field. It treats additional problems including difficulties of visual attention and concentration, which may manifest as an inability to sustain focus or to shift focus from one area of space to another. The ability to shift the focus of visual attention from one place in space to another affects many aspects of life including reading, most vocations and most avocations. Eye doctors may also prescribe vision therapy to sufferers from eye strain and visually-induced headaches. However, not all such therapy is limited to disorders of the visual system. Professional athletes, for example, may use vision therapy to enhance sensitivity to peripheral vision on the playing field or increase responsiveness to fast moving objects.
As a result of this expansion and ensuing confusion over what the term "vision therapy" includes, there is some controversy as to the use of vision therapy for individuals with learning disorders.
Although ophthalmologists and orthoptists often perform several components of visual therapy, most non-strabismic VT is performed by optometrists.
Major optometric organizations, including the American Optometric Association, the American Academy of Optometry, the College of Optometrists in Vision Development, and the Optometric Extension Program, support the assertion that vision therapy does not directly treat learning disorders, but rather addresses underlying visual problems which are claimed to affect learning potential.
Advocates cite a number of indications for the use of vision therapy. Some assert that poor eye tracking affects reading skills, and that improving tracking can improve reading.
In 1988, a review of 238 scientific articles was published in the Journal of the American Optometric Association defining vision therapy as "a clinical approach for correcting and ameliorating the effects of eye movement disorders, non-strabismic binocular dysfunctions, focusing disorders, strabismus, amblyopia, nystagmus, and certain visual perceptual (information processing) disorders." The paper concluded, "It is evident from the research that there is scientific support for the efficacy of vision therapy in modifying and improving oculomotor, accommodative, and binocular system disorders, as measured by standardized clinical and laboratory testing methods for patients of all ages for whom it is properly undertaken and employed.
A 2005 review concluded that "small controlled trials and a large number of cases support the treatment of convergence insufficiency. Less robust, but believable, evidence indicates visual training may be useful in developing fine stereoscopic skills and improving visual field remnants after brain damage. As yet there is no clear scientific evidence published in the mainstream literature supporting the use of eye exercises in the remainder of the areas reviewed, and their use therefore remains controversial."
Convergence insufficiency is a common binocular vision disorder characterized by asthenopia, eye fatigue and discomfort. Asthenopia may be aggravated by close work and is thought by some to contribute to reading inefficiency. In 2005, the Convergence Insufficiency Treatment Trial published two large, randomized clinical studies examining the efficacy of orthoptic vision therapy in the treatment of symptomatic convergence insufficiency. Although neither study examined reading efficiency or comprehension, both demonstrated that in-office vision therapy was more effective than "pencil pushups" (a commonly prescribed home-based treatment) for improving the symptoms of asthenopia and the convergence ability of the eyes. The design and results of at least one of these studies has been met with some reservation, questioning the conclusion as to whether intensive office-based treatment programs are truly more efficacious than a properly implemented home-based regimen.
In 2006, noted neurologist Oliver Sacks published a case study about "Stereo Sue", a woman who had regained her stereo vision, absent for 25 years, after undergoing vision therapy. The article was published in The New Yorker magazine, which is not peer-reviewed, very few details were given of the exact therapies used and the article discussed only one case of stereo rehabilitation. Caution should therefore be advised in interpreting Sacks' conclusions.
Optometrists take a slightly different view. In 1999 a joint statement by the American Academy of Optometry, the American Optometric Association, the College of Optometrists in Vision Development and Optometric Extension Program Foundation reported: "Many visual conditions can be treated effectively with spectacles or contact lenses alone; however, some are most effectively treated with vision therapy....Research has demonstrated that vision therapy can be an effective treatment option for ocular motility problems, non-strabismic binocular disorders, strabismus, amblyopia, accommodative disorders (and) visual information processing disorders."
Although skeptics assert that vision therapists may have a financial bias in proclaiming the efficacy of the practice, proponents and advocates of vision therapy claim that other eye professionals have a similar bias in rejecting its claims.
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