I was talking to a Reuters reporter the other day and learned of a new acupuncture study out of China, this one about amblyopia, or “lazy eye”. Amblyopia is a common and interesting visual problem. During development of the visual system if an eye is understimulated, the brain will not process data coming from that eye correctly, leading to a decrease in vision in the eye, despite the eye itself being structurally normal. There are several types of amblyopia, the most common of which is called “anisometropic”, but we’ll use the simpler word “refractive”.
Refractive amblyopia can be treated successfully, even when detected relatively late. Standard treatment involves correcting “normal” visual problems (that is, making sure the child is using glasses if they need them) and encouraging use of the lazy eye, often by patching the good eye. The authors of the current study reasoned that because it can be difficult and embarrassing for children to wear eye patches, and because they believe in acupuncture, a randomized controlled trial of acupuncture for amblyopia would be a good idea.
It’s actually a spectacularly bad idea, but you shouldn’t take my word for it. Let’s examine the study.
Let me first reassure you that the techniques used did not involve inserting needles into children’s eyeballs. But that’s about all the reassurance I can give. This study fails the initial “sniff test” for plausibility. There is no anatomic or physiologic reason that sticking needles into a child should affect their amblyopia (although I suppose if the needles were sufficiently painful and placed only in the visual field of the lazy eye…).
This fact in and of itself essentially invalidates the study. But let’s just suppose for a moment that there was some valid reason for thinking that acupuncture might work.
Not-So Blind, Not So Random
This particular study lends itself to far too many puns, but one of the first and most obvious problems with this study is its lack of blinding, that is, every researcher and patient knows what treatment is being given. Also, subjects (or victims?) of this experiment were recruited from eye clinics. They were not, for example, chosen serially (at least as reported). This can introduce bias into the experiment. For example, parents responding to recruitment announcements might be more predisposed to “believe in” acupuncture, and therefore be more responsive to placebo effects.
All subjects of the experiment were wearing the usual corrective lenses for several months on entry to the study. They were measured for new glasses if needed, and then randomized to either eye patching or acupuncture. Both sets of patients continued to use corrective lenses. The control (patching) group was instructed to use the patch for two hours a day and do near-vision activities. This is reasonably standard, although longer periods are often used.
The test group was subjected to acupuncture an also instructed to do near-vision activity, but without the patch.
What the researches found was that the groups had similar improvements in vision, or in study-speak, that acupuncture was non-inferior to patching. They interpret this as meaning that acupuncture may be a nice alternative to patching for similar kids with lazy eye. Is that what the results really say?
Well, no. In studies of amblyopia, especially in older children as in this study, many (about a quarter) improve significantly with eyeglasses alone. Children in both groups received this standard therapy. Also, although two hours of patching has in some studies been found to be as good as longer periods, this is the bare minimum of patching time that is used. This study did not include longer (and perhaps more typical) patching times.
This is one of the serious flaws in this study and any conclusions drawn from it—this study says nothing about acupuncture, because there was no adequate control group. It might have been interesting to compare the two groups to a spectacles-only group—perhaps both acupuncture and 2-hour eye patching were equally ineffective, rather than equally effective.
But of course the fatal flaw is the one stated by the authors:
Although the treatment effect of acupuncture appears promising, the mechanism underlying its success as a treatment for amblyopia remains unclear.
The underlying mechanism is unclear because there is none. No effect has been shown, and if it were, given the biologic implausibility, almost any explanation would be preferred to “the acupuncture did it”.
While a better-designed study might be intellectually interesting, it would be ultimately useless and immediately unethical. Acupuncture is more invasive than standard therapy and there is no reason to think it has any real advantages. I find little comfort in the fact that the study was approved by an institutional review board and published in a major peer-reviewed journal.
Zhao, J., Lam, D., Chen, L., Wang, Y., Zheng, C., Lin, Q., Rao, S., Fan, D., Zhang, M., Leung, P., & Ritch, R. (2010). Randomized Controlled Trial of Patching vs Acupuncture for Anisometropic Amblyopia in Children Aged 7 to 12 Years Archives of Ophthalmology, 128 (12), 1510-1517 DOI: 10.1001/archophthalmol.2010.306