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Vision therapy (VT) is an umbrella term for a variety of treatments based around eye exercises. The treatments aim to treat convergence insufficiency – for which there is supporting evidence – and a range of neurological, educational and spatial difficulties – uses which are not supported by good evidence.
Vision therapy can be prescribed when a comprehensive eye examination indicates that it is an appropriate treatment option. The specific program of therapy is based on the results of standardized tests and the person's signs and symptoms. Programs typically involve eye exercises and the use of lenses, prisms, filters, occluders, specialized instruments, and computer programs. The course of therapy may last weeks to several years, with intermittent monitoring by the eye doctor.
Definition and scope
Vision therapy is a broad concept that encompasses a wide range of treatment types. These include those aimed at convergence insufficiency – where it is often termed "vergence therapy" or "orthoptic therapy" – and at a variety of neurological, educational and spatial difficulties.
There exist a few different broad classifications of vision treatment philosophies, which have been traditionally divided between Optometrists, Ophthalmologists, and practitioners of alternative medicine:
- Orthoptic Vision Therapy, also known as orthoptics.
- Orthoptics is a field pertaining to the evaluation and treatment of patients with disorders of the visual system with an emphasis on binocular vision and eye movements. Commonly practiced by orthoptists, optometrists, behavioral optometrists, pediatric ophthalmologists, and general ophthalmologists, traditional orthoptics addresses problems of eye strain, visually induced headaches, strabismus, diplopia and visual related skills required for reading.
- Behavioral Vision Therapy, or visual integration vision therapy (also known as behavioral optometry).
- Alternative Vision Therapy: There have been a number of other approaches which have not been studied in traditional medicine, though which some patients feel give them relief. These methods are commonly under scrutiny by ophthamlological and optometric journals. These alternative therapies are commonly practiced by unlicensed professionals, though a minority of optometrists also provide them.
Orthoptic vision therapy
Orthoptics emphasises the diagnosis and non-surgical management of strabismus (wandering eye), amblyopia (lazy eye) and eye movement disorders. Evidence to support its use in amblyopia is unclear as of 2011.
Much of the practice of orthoptists concerns refraction and muscular eye control. Orthoptists are trained professionals who specialize in orthoptic treatment. With specific training, in some countries orthoptists may be involved in monitoring of some forms of eye disease, such as glaucoma, cataract screening and diabetic retinopathy 
Behavioral vision therapy
Behavioral VT aims to treat problems including difficulties of visual attention and concentration, which behavioral optometrists classify as visual information processing weaknesses. These manifest themselves as an inability to sustain focus or to shift focus from one area of space to another. Some practitioners assert that poor eye tracking may impact reading skills, and suggest that vision training may improve some of the visual skills helpful for reading.
Behavioral Vision Therapy is practiced primarily by optometrists who specialize in the area. Historically, there has been a difference in philosophy among optometry and medicine regarding the efficacy and relevance of vision therapy: Major organizations, including the International Orthoptic Association and the American Academy of Ophthalmology have concluded that there is no validity for clinically significant improvements in vision with Behavioral Vision Therapy, and therefore do not practice it. However, 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 non-strabismic visual therapy does address underlying visual problems which are claimed to affect learning potential. These optometric organizations are careful to distinguish, though, that vision therapy does not directly treat learning disorders.
A more recent (2005) review concluded less positively that: "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."
In 2006, noted neurologist Oliver Sacks published a case study about "Stereo Sue", a woman who had regained her stereo vision, absent for 48 years, after undergoing vision therapy. The article was published in The New Yorker magazine, which is fact-checked but not peer-reviewed, very few details were given of the exact therapies used and the article discussed only one case of stereopsis recovery. However, the woman described by Sacks, Susan Barry, a neurobiology professor at Mt. Holyoke College, subsequently published a book, "Fixing My Gaze." The book discusses multiple case histories and details the therapy procedures and the science underlying them.
A systematic review of the literature on the effects of vision therapy on visual field defects published in 2007 concluded that it was unclear to what extent patients benefited from vision restoration therapy (VRT) as "no study has given a satisfactory answer." The authors concluded that scanning compensatory therapy (SCT) seemed to provide a more successful rehabilitation, and simpler training techniques, therefore they recommended SCT until the effects of VRT could be defined.
A 2008 review of the literature concluded that "there is a continued paucity of controlled trials in the literature to support behavioral optometry approaches. Although there are areas where the available evidence is consistent with claims made by behavioral optometrists ... a large majority of behavioral management approaches are not evidence-based, and thus cannot be advocated."
Other than for strabismus (such as intermittent exotropia) and convergence insufficiency, the consensus among ophthalmologists, orthoptists and pediatricians is that non-strabismic visual therapy lacks documented evidence of effectiveness. In 1998, the American Academy of Pediatrics, American Academy of Ophthalmology, and American Association for Pediatric Ophthalmology and Strabismus issued a policy statement regarding the use of vision therapy specifically for the treatment of learning problems and dyslexia. According to the statement: "No scientific evidence exists for the efficacy of eye exercises ('vision therapy')... in the remediation of these complex pediatric neurological conditions." More recently, in 2004, the American Academy of Ophthalmology released a position statement asserting that there is no evidence that vision therapy retards the progression of myopia, no evidence that it improves visual function in those with hyperopia or astigmatism, or that it improves vision lost through disease processes. This was also supported by the International Orthoptic Association.
The Joint Statement mentioned above was criticised at the time by Merrill Bowan, a vision therapy enthusiast, for being biased, with the author of a rebuttal concluding "The AAP/AAO/AAPOS paper contains errors and internal inconsistencies. Through highly selective reference choices, it misrepresents the great body of evidence from the literature that supports a relationship between visual and perceptual problems as they contribute to classroom difficulties.". The author also states that the Joint Statement presents an unsupported opinion by implication that Optometrists claim that vision therapy cures the learning problem. A similar criticism could be leveled at the 2004 American Academy of Ophthalmology paper which implies that vision therapy is claimed to treat "vision lost through disease processes". There is a common theme that critics of vision therapy seem to do by placing vision therapy under the same banner with alternative therapies. By implication, the lack of evidence for the alternative therapies is cited as a lack of evidence for vision therapy. No supporting evidence is given that vision therapy is actually used to treat eye disease or vision lost through disease processes.
Some 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."
Practitioners in Behavioral optometry (also known as functional optometrists or optometric vision therapists) practice methods that have been characterized as a complementary alternative medicine practice. A review in 2000 concluded that there were insufficient controlled studies of the approach and a 2008 review concluded that "a large majority of behavioural management approaches are not evidence-based, and thus cannot be advocated."
The consensus among Ophthalmologists, Orthoptists and Pediatricians is that "visual training" in non-strabismic Behavioural Vision therapy lacks documented scientific evidence of effectiveness. Although Ophthalmologists and Orthoptists believe that exercises can improve binocular vision control, they believe it does not purely improve monocular visual acuity such as that in amblyopia (rather, occlusion is the therapy of choice), change a person's refractive error. It is probable that they do not change the accommodative/convergence ratio nor change the amplitude of accommodation to postpone or delay presbyopia. It has been considered that they are unlikely to a person to develop the ability for stereopsis; nonetheless recent experimental investigations into dedicated perceptual learning exercises, inspired by Barry's recovery of stereopsis, have shown some promise.
Behavioral optometry is a branch of optometry that explores how visual function influences a patient's day-to-day activities. Vision therapy is a subset of behavioral optometry. In general, vision therapists attempt to improve vision, and therefore day-to-day well-being, of patients using "eye exercises," prism, and lenses, with more emphasis on the patient's visual function. Among schools of medicine, ophthalmology does not see merit in the procedures surrounding many of behavioral optometry's practices, arguing that there have not been enough studies of high enough merit to warrant practicing of vision therapy.
In a 2008, vision scientist Brendan Barrett published a review of behavioral optometry at the invitation of the UK College of Optometrists. Barrett wrote that behavioral optometry was not a well-defined field but that it was sometimes said to be an "extension" to optometry, taking a holistic approach: practitioners of the therapy use techniques outside mainstream optometry to "influence the visual process". Barrett discussed these techniques under ten headings:
- Vision therapy for accommodation/vergence disorders – eye exercises and training to try and alleviate these disorders. There is evidence that convergence disorders may be helped by eye exercises, but no good evidence exercises help with accommodation disorders. 
- The underachieving child – therapies claimed to help children with dyslexia, dyspraxia and attention deficit disorder – a "vulnerable" target market. There is no evidence that behavioral optometry is of any benefit in relation to these conditions.
- Prisms for near binocular disorders and for producing postural change – the use of "yoked" prisms to redirect a person's gaze and bring about a range of claimed benefits including postural improvements and increased wellbeing. There is a lack of evidence for the effect this approach may have.
- Near point stress and low-plus – the use of special lenses to adjust near-field vision, even for people who would not normally need glasses. This is claimed to bring about postural benefits and relieve visual stress. Some research has been carried out in this area and its effectiveness remains "unproven".
- Use of low-plus lenses at near to slow the progression of myopia
- Therapy to reduce myopia
- Behavioural approaches to the treatment of strabismus and amblyopia
- Training central and peripheral awareness and syntonics
- Sports vision therapy
- Neurological disorders and neurorehabilitation after trauma/stroke.
Barrett noted the lack of published controlled trials of the techniques. He found that there are a few areas where the available evidence suggest that the approach might have some value, namely in the treatment of convergence insufficiency, the use of yoked prisms in neurological patients, and in vision rehabilitation after brain disease or injury—but he found that in the other areas where the techniques have been used, the majority, there is no evidence of their value. In contrast, Steven Novella points out that the only condition that there is good quality scientific evidence for is convergence disorders. This points out a problem that is common with Complementary or integrative medicine, a type of Alternative medicine, is that a promising use for treating a single disorder is applied to a wide range of disorders for which there is no evidence.
The eye exercises used in vision therapy can generally be divided into two groups; those employed for "strabismic" outcomes and those employed for "non-strabismic" outcomes, to improve eye health. Ophthalmologists and orthoptists do not endorse these exercises as having clinically significant validity for improvements in vision. Usually, they see these perceptual-motor activities being in the sphere of either speech therapy or occupational therapy.
Some of the exercises used are
- Near point of convergence training, or the ability for both eyes to focus on a single point in space,
- Base-out prism reading, stereogram cards, computerized training programs are used to improve fusional vergence.
- The wearing of convex lenses
- The wearing of concave lenses
- "Cawthorne Cooksey Exercises" also employ various eye exercises, however, these are designed to alleviate vestibular disorders, such as dizziness, rather than eye problems.
- Antisuppression exercises - this is no longer commonly practiced, although occasionally it may be used.
The eye exercises used in Behavioural Vision Therapy, also known as Developmental Optometry is practiced primarily by Behavioural Optometrists. Behavioral Vision Therapy aims to treat problems including difficulties of visual attention and concentration, which may manifest themselves as an inability to sustain focus or to shift focus from one area of space to another.
Some of the exercises[clarification needed] used are:
- Marsden balls
- Rotation trainers
- Balance board/beams
- Saccadic fixators
- Directional sequencers
Fusional Amplitude and Relative Fusional Amplitude training[clarification needed]
- Designed to alleviate convergence insufficiency. The CITT study (Convergence Insufficiency Treatment Trial) was is a randomized, double-blind multi-center trial (high level of reliability) indicates that Orthoptic Vision Therapy is an effective method of treatment of convergence insufficiency (CI). Both optometry and ophthalmology were co-authors of this study.
- Designed to alleviate intermittent exotropia or other less common forms of strabismus.
Certain do-it-yourself eye exercises are claimed by some to improve visual acuity by reducing or eliminating refractive errors. Such claims rely mainly on anecdotal evidence, and are not generally endorsed by orthoptists, ophthalmologists or optometrists. Chinese school children always do eye exercises twice per day during school, which are compulsory. They are also part of other forms category's as they are also do-it-yourself exercises although quite a few scientists say that they actually harm the children's eyes
Conceptual basis and effectiveness
Behavioral optometry is largely based on concepts which lack plausibility or which contradict mainstream neurology, and most of the research done has been of poor quality. As with chiropractic, there seems to be a spectrum of scientific legitimacy among practitioners: at one extreme there is some weak evidence in support of the idea that myopia may be affected by eye training; at the other extreme are concepts such as "syntonic phototherapy" which proposes that differently colored lights can be used to treat a variety of medical conditions.
A review in 2000 concluded that there were insufficient controlled studies of the approach. In 2008 Barrett concluded that "the continued absence of rigorous scientific evidence to support behavioural management approaches, and the paucity of controlled trials in particular, represents a major challenge to the credibility of the theory and practice of behavioural optometry."
Behavioral optometry has been proposed as being of benefit for children with Attention deficit hyperactivity disorder and autism – this proposal is based on the idea that since people with these conditions often have abnormal eye movement, correcting this may address the underlying condition. Evidence supporting this approach is however weak; the American Academy of Pediatrics, the American Academy of Ophthalmology and the American Association for Pediatric Ophthalmology and Strabismus have said that learning disabilities are neither caused nor treatable by visual methods.
Behavioral optometry is considered by some optometrists to have its origins in orthoptic vision therapy. However, Vision therapy is differentiated between strabismic/orthoptic vision therapy (which many Optometrists, Orthoptists and Ophthalmologists practice) and non-strabismic vision therapy. A.M. Skeffington was an American optometrist known to some as "the father of behavioral optometry". Skeffington has been credited as co-founding the Optometric Extension Program with E.B. Alexander in 1928.
A review in 2000 concluded that there were insufficient controlled studies of the approach and a 2008 review concluded that "a large majority of behavioral management approaches are not evidence-based, and thus cannot be advocated."
Sports Vision Training
Alternative Vision Therapy
Alternative vision therapies include methods that some patients feel subjectively help them. Many optometrists and ophthalmologists are skeptical of the efficacy of these methods and practices, though some have been found to have at least a basis in studied principles to some limited degree (such as syntonics and melanopsin, TBI and tinted lenses, and the adoption of EMDR by the VA Hospital in the USA).
- Syntonic Phototherapy & the Irlen Method
- The Bates method
- The Neo-Reichian approach
- Eye Movement Desensitization and Reprocessing (EMDR)
Some physicians are skeptical about the efficacy of "vision therapy" stating that it lacks data and is mostly anecdotal. In 2009, the American Academy of Pediatrics along with the American Academy of Ophthalmology "essentially declared war" on developmental optometry, as Judith Warner wrote in a New York Times article. Even within the field of optometry the U.K. College of Optometrists noted the "Continued absence of rigorous scientific evidence to support behavioral management approaches" in the second college of Optometrists report. The American Academy of Pediatrics is also critical of behavioral optometry. In 2009 it reviewed 35 years of the literature in support of vision therapy and issued a statement — in conjunction with other ophthalmological associations — condemning the therapy and its contention that it could help with learning disabilities. Visual problems, it claimed, are not the basis for learning disabilities. It issued a stern warning about the seductions of treatments that sound convincing but aren’t based on science: "Ineffective, controversial methods of treatment such as vision therapy may give parents and teachers a false sense of security that a child’s learning difficulties are being addressed, may waste family and/or school resources and may delay proper instruction or remediation." The website by the American Association for Pediatric Ophthalmology and Strabismus states: "Behavioral vision therapy is considered to be scientifically unproven" and "There is no evidence that vision therapy delays the progression or leads to correction of myopia."
Various forms of visual therapy have been used for centuries. The concept of vision therapy was introduced in the late nineteenth century for the non-surgical treatment of strabismus. This early and traditional form of vision therapy was the foundation of what is now known as orthoptics.
In the first half of the twentieth century, orthoptists, working with ophthalmologists, introduced a variety of training techniques mainly designed to improve binocular function. In the second half of the twentieth century, vision therapy began to be used by optometrists and paramedical personnel to treat conditions ranging from uncomfortable vision to poor reading and academic performance. It has also been claimed specifically to improve eyesight, and even to improve athletic performance.
At the beginning of the twenty-first century, most vision therapy is done by optometrists, while traditional orthoptics continues to be practiced by orthoptists and ophthalmologists. Based on assessments of claims and studies of published data, ophthalmologists claim that, except for near point of convergence exercises, vision therapy lacks documented evidence of effectiveness.
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