There are far too many specific types of medical pseudoscience to address fully, even with a daily blog. It often seems that new ones are created faster than we can address existing dubious treatments, products, and health claims. That is why it is critical that we focus on basic concepts – the red flags that should warn away from probable quackery.

Let’s take a look at vision therapy – the notion that exercises and special glasses can treat a long list of behavioral and learning problems which therapists claim are ultimately caused by vision problems.

A cure for everything

The first red flag or feature of possible quackery that comes up is the claim that there is one cause, and therefore one cure, for a long list of diseases and disorders that do not seem to be connected. Some chiropractors, for example, claim that cracking the back can address just about any medical problem, while medical acupuncturists would treat everything from addiction to cancer by sticking needles in the skin.

The core claim of vision therapists, or behavioral optometrists, is that many children are misdiagnosed with learning and behavior disorders when in fact they have a subtle problem with vision:

According to the American Optometric Association, “studies indicate that 60 percent of children identified as “problem learners” actually suffer from undetected vision problems and in some cases have been inaccurately diagnosed with attention deficit disorder (ADD) or attention deficit hyperactivity disorder (ADHD).”

That is a pretty dramatic claim, utterly lacking in evidence. As with many dubious health claims, the scientific evidence has been heading in quite a different direction. It is increasingly clear, for example, that dyslexia is not a problem with vision but with the brain’s processing of language. Attention deficit, likewise, is a problem with the brain’s executive function. These are simply not problems with vision or visual processing.

Historically what often happens with scientifically dubious health practices is that they are based on a core notion that is never validated, or even critically evaluated. Science needs to proceed in a careful and conservative manner – only building on rock solid ground. However, it is easy to elaborate the trappings of science without such solid founding. The core belief becomes a tenet of faith, not questioned or seriously studied, but just taken for granted.

This is especially troublesome in medicine, because outcomes are often subjective, clinical research is extremely difficult, and anecdotes can be highly misleading. In fact it is difficult to interpret clinical evidence without knowing the basic science plausibility. Even when that plausibility is zero, an entire profession can evolve from a spurious basis.

A loose approach to evidence

Looking back over the last century of medical science it is also clear that a rigorous approach to medical evidence is required in order to know what really works. Researcher bias, publication bias, citation bias, placebo effects, statistical errors, and the occasional fraud make it possible to create the false impression that anything works – no matter how absurd. It takes time, care, critical analysis, and methodological rigor to sort out what really works from all this self-deception.

Taking even a slightly loose approach to evidence can create the impression of being evidence-based, even when the truth is very different.

Behavioral optometrists often rely on anecdotal evidence to support their claims. It is no surprise that many of their interventions might seem to subjectively work. First, they are targeting a vulnerable population. Parents and children are often frustrated by learning and behavioral problems, and may be dissatisfied with the range of treatments offered and their effectiveness. The public is also primed with the usual tropes – treat the underlying true cause, not the symptoms, and be wary of “Big Pharma”. Behavioral optometrists are selling what people want, a cure without drugs or surgery.

Further, the outcomes are highly subjective and susceptible to placebo effects. As with any psychological intervention, the very fact that a treatment is being offered may lead to hope, or to greater confidence. There may also be a profound observer effect, and parents will feel pressured to validate the expense of the treatments and their choice to pursue what may seem like an unusual course.

For all these reasons we need to conduct careful clinical research and control for variables as best as we can. When we do that, we find that behavior optometry is not, in fact, based on evidence.

A systematic review of the last thirty years of research found:

The headings selected were: (1) vision therapy for accommodation/vergence disorders; (2) the underachieving child; (3) prisms for near binocular disorders and for producing postural change; (4) near point stress and low-plus prescriptions; (5) use of low-plus lenses at near to slow the progression of myopia; (6) therapy to reduce myopia; (7) behavioural approaches to the treatment of strabismus and amblyopia; (8) training central and peripheral awareness and syntonics; (9) sports vision therapy; (10) neurological disorders and neuro-rehabilitation after trauma/stroke. There is a continued paucity of controlled trials in the literature to support behavioural optometry approaches. Although there are areas where the available evidence is consistent with claims made by behavioural optometrists (most notably in relation to the treatment of convergence insufficiency, the use of yoked prisms in neurological patients, and in vision rehabilitation after brain disease/injury), a large majority of behavioural management approaches are not evidence-based, and thus cannot be advocated.

Essentially there is reasonable evidence for eye exercises to treat convergence insufficiency – which is a disorder of eye movements. This has plausibility, and the evidence is reasonable. There is some evidence for benefit with patients recovering from a stroke or injury, likely due to brain plasticity as it tries to compensate for the damage. However, this literature is plagued with the problem of separating normal recovery from a treatment effect, and also functional recovery (performing specific tasks better because of practice) from neurological recovery (improving the connections in the brain). But being generous, these two areas, where there is the greatest plausibility, show some evidence of efficacy.

All other claims by behavioral optometrists, however, relating to behavior issues and visual problems not caused by eye muscle weakness, lack the kind of evidence necessary to conclude that treatments are effective.

This is also a common pattern that we see in dubious professions – there may be kernels of truth here and there, but the core philosophy is not valid and the majority of the less plausible claims are not true. Often proponents use the kernels to validate the whole, and this is also not legitimate.

Ophthalmologist David Guyton, interviewed about the issue, claims that only about 1% of patients (not the 60% claimed by behavior optometrists) have issues that respond to the exercises. Regarding the implication of this small kernel of validity he notes: “You really can’t validate by association.”

This is similar to chiropractic, in which manipulative therapy may have some benefit for acute uncomplicated lower back strain (a very limited indication at the plausible end of the spectrum) but that does not mean it treats otitis media.

Behavioral optometrists defend their claims by stating that ophthalmologists are being unfair, are overly skeptical, don’t really understand what they do, and are just protecting their turf. Such gratuitous dismissal of criticism is another red flag for quackery. In the end what matters is scientific plausibility and clinical evidence.

Unfortunately behavior optometry is now well embedded in the health care landscape, like many dubious treatments. Some optometrists are trying to expand their scope of practice beyond their true limited area of expertise. This is ultimately a challenge for the regulatory infrastructure. Having good science in health care only matters if practice is actually based on that science.


Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.