Letter to the Editor re: "Refractive and Vision Status in Down Syndrome: A Comparative Study".

Dear editor,

We would like to share our ideas on the publication “Refractive and Vision Status in Down Syndrome: A Comparative Study.”[1] Hashemi et al.[1] concluded that “In DS patients, the prevalence rates of refractive errors, amblyopia, and visual impairment are higher than those in non-DS individuals.” Regarding DS and refractive/vision problems, there should be a hypothesis for the clinical association. How DS might contribute to ocular problems should be proposed. In a recent report, the possible mechanism was cerebral visual impairment, not an intraocular problem.[2] This might not be concluded based on the findings of the present study. An important concern is about the control group. The control group is only a group of non-DS cases but not healthy controls. For example, “candidates for refractive surgery” must have an ocular problem. Additionally, Hashemi et al.[1] mentioned “age- and gender-matched normal controls,” but there were unequal numbers of subjects in the patient and control groups. Hence, there might be a methodological flaw and bias.