We thank Dr Kawada for his interest in and his constructive criticism of our article. However, there are a few points from his letter that we feel obliged to reply to.
This study was prospective. At our institution, to have suitable personnel available to reliably complete the ISI questionnaire in central serous chorioretinopathy (CSCR) patients, this will only be possible in a limited number of participants within a prospective study. In our study, the sample was limited to 40 patients and 40 controls. As we highlighted in the original article, this is a small number with a limited level of statistical power that nevertheless was sufficient to detect a significant difference in many parameters. Although large samples are preferable and give a greater degree of precision and surety, studies with smaller samples can also be sufficiently powered to detect large differences, as was the case with the very large differences in proportions of CSCR patients vs controls reporting steroid exposure, stress, and sleep disorders.
The difficulties of separating the sleep disturbance and shift work from one another were also recognized within our article. Furthermore, we urged other researchers to address this question with a specifically designed prospective study. We wished to raise the question: is sleep disturbance a pseudo-measure for shift work rather than the reverse? We foresee that within such a prospective study designed to examine the relationship between shift work, sleep disturbance, and CRSC, “long working hours” would also be addressed.
In addition, because these were independent groups of controls and CSCR patients and the participants were matched based on sex and age, eyes were not paired. Throughout, nonpaired statistics were used, which was stated within the statistics section of our article.
Finally, another study was recently published indicating similar results in a smaller cohort.