By Dr. Steven Novella
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.
Founder and Executive Editor of Science-Based
Medicine Steven
Novella, MD is an academic clinical neurologist at the
Yale University School of Medicine.
Article originally appeared at https://sciencebasedmedicine.org/vision-therapy-quackery