The Hammer & Nail Factor

hammer-and-nail-2You’ve likely heard this expression before, or some variation thereof:  “If your only tool is a hammer, everything starts to look like a nail”.  I’ve mentioned this in the context of prism glasses being used as a substitute for vision therapy.   Most of us don’t see the “easy asthenopia cases” any more.  We’re seeing ABI, ASD, SRD – complex problems requiring many tools in a vast shed.  For these populations VT requires a significant  commitment in time and resources on the part of the doctor and staff.  It would be much simpler to take an alternate route and prescribe prism glasses of some sort for every patient who walks through the door.  Let’s look at some of the implications of this approach.

We’ve visited this with regard to “the three Rs”: Reading, Writing, and Ritalin – and the risks of doling out any treatment approach like a Pez Dispenser.


So if we can lend that analogy to this problem, let’s call it the PEZ (Prism EZ) Factor.  There are guidelines that have been suggested for prescribing prism in a classical sense for so-called decompensated hetereophoria, and some have suggested that the concept of prism adpatation is overrated and therefore clinicians should be more aggressive in Rxing prism.  The debate about whether or not “prism is poison” dates back to at least 1920, the year my father was born, and he’s getting old. Over the past 30 years the discussion has slowly extended to yoked prisms.

Perhaps we can agree on this: prism is neither a poison nor a panacea.  Therefore it should always be considered, but not prescribed in wholesale fashion.  And by that I mean that it would be as illogical to claim that every patient with a visual performance issue needs a prism Rx as it would be that every orthopedic problem could be solved with a shoe lift to redistribute weight bearing, or that every auditory processing problem could be solved with a hearing aid of some sort.

The irony to me, and it bears repeating, is that the goal of optometric vision therapy is to provide the patient with sufficient learning opportunities so that they can become effective indpendent learners.  If we believe that vision is a form of intelligence, and that the flexibility of one’s adaptability is a meaure of intelligence, the idea of trying to substitute a prism Rx for vision therapy is at the very least counter-intuitive.

tumblr_lkir3yewjb1qcf4lvThe PEZ dispensing of yoked and micro-prisms merits some drum banging.  Don’t get me wrong: when they work, prisms are a marvelous first line intervention.  The cost is relatively minimal compared to office-based VT, and there is virtually no commitment in terms of time – a commodity as precious as currency these days.  The downside is that when prisms have no demonstrable effect, or only fleeting effects but are Rxed anyway, parents or other professionals may conclude that other forms of visual intervention are not likely to succeed.


2 thoughts on “The Hammer & Nail Factor

  1. Dr. Press: Thank you for your comment. I am also an optometrist working in a couple of clinics in upstate New York. Virtually on a daily basis I hear patients talking about going to England to see a certain optometrist who prescribes “prism glasses”. I hear at least secondhand reports of miraculous recoveries in children who prior to the application of the prism glasses were poor readers. As I have not really seen any of these patients I really cannot comment on the effect of the treatment or of any pre-existing visual anomalies.
    What bothers me the most is the apparent indiscriminate prescription and the “mysticism” surrounding the treatment. People who can ill afford the expense of the trip and the consultation and who will do anything for their children are putting themselves into debt based on the anecdotal experiences of other people.
    I would be happy to prescribe these glasses for my patients if I could find some evidence that they are effective. I also cannot find any particular information on the method of prescribing the glasses or on which patients I should prescribe the glasses. There is simply a lack of information. Certainly there are no rigorous studies for me to base a recommendation of sending these patients to England or elsewhere for these magical glasses.
    I really have an open mind about this issue. I also have in mind that idea to study the effect of the prism glasses. It would require the use of a Visagraph instrument to monitor the effect of prisms of various orientations on eye movements. I know that you have such an instrument in your office. Perhaps we can collaborate on such an experiment.
    Thanks again for your cogent message on this topic.

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