Although the number of studies with the same concentration in either the RCT or cohort groups was too small to evaluate the effect of atropine concentration fairly, we attempted to estimate this effect by combining RCT and cohort studies, thus providing larger samples. Combining the types of studies with Asian children, at least, was reasonable because they yielded similar effects. We thus compared low and high concentration using the sets of data listed in Fig. 2 in two separate analyses. The first was a comparison between the set of data for concentrations of 0.25% or less (n = 5) versus concentrations of 0.5% or more (n = 9) and the second a comparison between 0.5% or less (n = 8) versus 1% (n = 6). Using the nonparametric Mann-Whitney U test, the results yielded no significant difference for either comparison of atropine concentration, being U = 25, p = 0.79 and U = 18, p = 0.49, respectively.
In addition, myopic children in the real world are more likely to receive multiple interventions such as bifocal or progressive addition lenses,31 eyedrops, traditional Chinese medicine like acupuncture, and so on. On one hand, it is hard to persuade children and their parents to participate in an RCT with a single intervention without receiving any other. On the other hand, myopia is an ocular abnormality that occurs and develops involving many different mechanisms.39 Combined therapy may provide promising effectiveness and reduce worrying adverse effects for controlling myopia progression in children.22 Observational studies might be a good design to mitigate these concerns.
No. 1 Dongjiaominxiang Dongcheng District, Beijing
This work was supported by the Major State Basic Research Development Program of China (“973” Program, 2011CB504601), the Major International (Regional) Joint Research Project of the National Natural Science Foundation of China (81120108807), Beijing Nova Program (Z121107002512055), and the National Natural Science Foundation of China (81300797). Shi-Ming Li and Shan-Shan Wu contributed equally to this work.
Received July 16, 2013; accepted November 25, 2013.
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