behavioural optometry: pros and cons

MUSEC is Macquarie University’s Special Educational Centre. Since 2005 it has been issuing one-page briefings on various topics relevant to special education; a brilliant idea and very useful for busy teachers. One of the drawbacks of a one-page briefing is that if the topic is a complex one, there might be space for a simple explanation and a couple of references only. The briefings get round that problem, in part, by putting relevant references on a central website.  One of their briefings is about behavioural optometry.

Behavioural optometry is based on the assumption that some behavioural issues (in the broadest sense) are due to problems with the way the eyes function. This could include anything from poor convergence (eyes don’t focus together) to variations in processing visual information in different coloured lights. The theory is a plausible one; visual dysfunction can cause considerable discomfort and can affect balance and co-ordination, for example.

Behavioural optometrists are sometimes consulted if children have problems with reading, because reading requires fine-grained visual (and auditory) discrimination, and even small variations in the development of the visual system can cause problems for young children. One of the reasons systematic synthetic phonics programmes are so effective in helping young children learn to decode text is because they train children in making fine-grained distinctions between graphemes (and between phonemes). But phonics programmes cannot address all visual (or auditory) processing anomalies, which is the point where behavioural optometrists often come in.

The MUSEC briefing on behavioural optometry (Issue 33) draws on two references; a 2011 report by the American Academy of Paediatrics (AAP), and a 2009 review paper by Brendan Barrett, a professor of visual development at Bradford University.  Aspects of the briefing perplexed me.  I felt it didn’t accurately reflect the conclusions of the two references because it:

  • doesn’t discriminate between treatments
  • overlooks the expertise of behavioural optometrists
  • equates lack of evidence for efficacy with inefficacy
  • assumes that what is true for a large population must be true for individuals
  • gives misleading advice to readers.

Discrimination between treatments

In its second paragraph the briefing lists three types of treatment used by behavioural optometrists; lenses and prisms, coloured lenses or overlays, and vision therapy. But from paragraph four onwards, no distinction is made between treatments – they are all referred to as ‘behavioural optometry’ and evidence (for all behavioural optometry treatments presumably) is said to be ‘singularly lacking’. Since lenses and prisms are used in what Barrett calls traditional optometry (p.5), this generalization is self-evidently inaccurate. Nor does it reflect Barrett’s conclusions. Although he highlights the scarcity of evidence and lack of support for some treatments, he also refers to treatments developed by behavioural optometrists being adopted in mainstream practice, and to evidence that supports claims involving convergence insufficiency, yoked prisms, and vision rehabilitation after brain disease/injury.

Expertise of behavioural optometrists

The briefing also appears to overlook the fact that behavioural optometrists are actually optometrists – a protected title, in the UK at least. As such, they are qualified to make independent professional judgments about the treatment of their patients. As Barrett points out, some of the controversies over treatments involve complex theoretical and technical issues; behavioural optometry isn’t the equivalent of Brain Gym. But teachers are unlikely to know that if they only read the briefing and not the references.

Lack of evidence for efficacy

Both references cited by the MUSEC briefing are reviews commissioned by professional bodies. Clearly, the American Academy of Pediatrics, the College of Optometrists or MUSEC cannot endorse or advocate treatments for which there is little or no evidence of efficacy. But individual practitioners are not issuing policy statements, they are treating individual patients. If they are using treatments for which a robust evidence base is lacking, that’s unsatisfactory, but a weak evidence base doesn’t mean that there is no evidence for efficacy, nor that the treatments in question are ineffective. Setting up RCTs of treatments for complex issues like ‘learning difficulties’ is challenging, expensive and time-consuming. As a parent, I would far rather my child try treatments that had a weak evidence base but were recommended by experienced practitioners, than wait for the Cochrane reviewers to finish a task that could take decades.

Populations vs individuals

The briefing paper says that “there is clear consensus among reading scientists that visual perception difficulties are rarely critical in reading difficulties and that the problem is typically more to do with language, specifically phonological processing.

Although this statement is right about the consensus and the role of phonological processing, one can’t assume that what’s true at a population level is true for every individual. Take, for example, convergence insufficiency (one of the areas where Barrett found evidence to support behavioural optometrists’ claims). According to the AAP report, the prevalence of convergence insufficiency is somewhere between 0.3% and 5% of the population (p.832).   So the probability of any given child having convergence insufficiency is low, but in the UK it still could affect up to 500,000 children. Although the report found no evidence that convergence insufficiency causes problems with decoding, comprehension or school achievement, it points out that it ‘can interfere with the ability to concentrate on print for a prolonged period of time’.   So even though in theory convergence insufficiency could be contributing to the difficulties of a quarter of the UK’s reluctant readers, it isn’t screened for in standard eye tests.

Advice to readers

The briefing recommends visual assessment for problems with acuity and refractive or ‘similar’ problems, but that’s not what the AAP recommends. It says:

Children with suspected learning disabilities in whom a vision problem is suspected by the child, parents, physicians, or educators should be seen by an ophthalmologist who has experience with the assessment and treatment of children, because some of these children may also have a treatable visual problem that accompanies or contributes to their primary reading or learning dysfunction.” (p. 829)

In the UK, that would require considerable persistence on the part of the child, parent or educator, although physicians might have more success.

The briefing also suggests an alternative to behavioural optometry; ‘explicit instruction in the specific areas causing difficulty’. Quite how ‘explicit instruction’ would improve problems with eye tracking, visual processing speed, visual sequential memory, visual discrimination, visual motor integration, visual spatial skills and rapid naming, never mind attention or dyspraxia where the difficulty is often discovered because the child is unable to carry out explicit instructions, is unclear.

Conclusion

I’m not claiming that behavioural optometry ‘does help children with reading difficulties’ because I don’t know whether it does or not. But that appears to be the nub of the problem – in the absence of evidence nobody knows whether it does or not. Nor which treatments help, if any. As the AAP paper says “Although it is prudent to be skeptical, especially with regard to prematurely disseminated therapies, it is important to also remain openminded.” (p.836)

I also had problems with the MUSEC briefing’s reading of Barrett’s conclusions. Although I wouldn’t go so far as to say the briefing is wrong (except perhaps about the lenses, and I’m not sure what it means by ‘explicit instruction’), its take-home message, for me, was that behavioural optometrists lack competence, that visual problems are unlikely to play any part in developmental abnormalities, and that if there are visual problems they will be limited to acuity and refractive or ‘similar’ factors. That’s not the message I got from either of the papers cited by the briefing. Obviously, on one side of A4, the authors couldn’t have covered all the relevant issues, but I felt that what they included and omitted could give the wrong impression to anyone unfamiliar with the issues.

References

American Academy of Pediatrics (2011). Joint technical report – Learning disabilities, dyslexia, and vision. Pediatrics, 127, e818-e856.

Barrett, B.T. (2009). A critical evaluation of the evidence supporting the practice of behavioural vision therapy. Ophthalmic and Physiological Optics, 29, 4-25.

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