Survey responses are more subject to errors of memory if they are rare events occurring far in the past. The use of night light is by no means a rare event. It takes place over a period of years and may even be a behavior that is continuing into the present for a particular study child or his siblings. We find it highly unlikely that parents cannot recall the correct use of night lights for their school-aged children. A final criticism is that parents may not have answered accurately because they were aware of the previous study s results.
Surveys are a standard tool in epidemiologic research.
The potential for recollection and response bias must be evaluated within each study rather than with a blanket indictment. Our assessment is that neither source of bias can account for the discrepancy between the two studies. In summary, we do not find that there is any link between nighttime nursery lighting and future childhood myopia in a representative sample of school-aged children and believe that parents should not concern themselves with this unfounded risk.