Sir,

The authors would like to thank Dr Cheung and colleagues for their letter and interest in the article.1 The authors agree with Dr Cheung and colleagues that for the descriptions of the correlations between the epiretinal membranes and the ocular and general parameters, the correlation coefficient, the P-value, and the 95% confidence intervals of the odds ratios were given, while the odd ratios themselves were omitted. The description of the statistical analysis would have been considerably more precise, if the odds ratios had additionally been given, which now can only be estimated from their 95% confidence intervals in the manuscript.

The authors also agree with Dr Cheung et al that, as also pointed in the article,1 differences in the grading method including use of monoscopic versus stereoscopic photographs may be one of the reasons for the differences in the prevalence rates of the epiretinal membranes between the various studies. In addition, as Dr Cheung and colleagues point out, nuclear cataract may have prevented the delectability of epiretinal membranes in some eyes with considerable cataract.

Although the intra-observer repeatability of the assessment of the epiretinal membranes was not measured in the Beijing Eye Study, the grader was trained and repeatedly checked by a panel of experienced clinicians, particularly in cases of doubt.

In summary, the authors completely agree with Dr Cheung in his constructive criticism of the weak points of the study and thank him and his colleagues for their remarks.