We reported that the corneal endothelial cell density (ECD) decreased progressively for up to 24 months after Ahmed glaucoma valve surgery. By mentioning the inborn error in calculating the ECD in the article, we intended to show that the degree of change noted was not an absolute value, but that there might be some variation. Measurement of the corneal ECD count and evaluation of the morphology using specular microscopy have limited repeatability and reproducibility, especially when we are measuring the peripheral cornea. Nevertheless, we are very confident regarding the results of specular microscopy performed in our clinic, as the technician involved in this study was very well trained and had sufficient experience. In addition, the technician was masked about the study patients. Moreover, we applied the “dot method” of noncontact-type specular microscopy (Noncon Robo SP-8000, Konan Medical Inc, Tokyo, Japan) when measuring corneal ECD and morphology. This is useful when determining cell loss and evaluating changes in morphology, and it differs from the fixed-frame method.
We agree that cells might be distributed irregularly throughout the endothelium. This happens even within the field of analysis. To reduce this type of error, we marked 80 to 100 contiguous cells in the calculation instead of 50 cells (the minimum recommended number). In addition, since no statistically significant change in morphology was observed in this study, we do not think that an irregular distribution of the cells was very probable.
The baseline ECD count in the supratemporal area in the control was incorrectly reported as 2152 ± 658 at baseline in Table 3. This should be 2550 ± 589 at baseline, as shown in Figure 1. We apologize for our error. An erratum appears in this issue of the journal (pages 691–692) rectifying this error. The remaining numbers in the table are correct.
The change in the morphology of corneal endothelial cells in our study was not statistically significant. Nevertheless, this does not mean that there is no change at all, just that the changes do not reach significance ( P values from .080 to .946). One may find that the coefficients of variation in cell size were increased irregularly at different time points and in different areas during follow-up. In general, however, the values tended to settle in the later stage. The same phenomenon was found in the pleomorphism; the percentage of hexagonal cells decreased to a small degree and then tended to recover over time.
We apologize for not including confidence intervals in our article. However, adding confidence intervals would have made the table too complicated and difficult to express the results in the same table. As Dr Chandra Sekhar mentioned, the confidence intervals overlap. Nevertheless, we do not believe that this changes the results. It means there was considerable variation in the degree of decrease in the cell count, although there was a constant tendency for the ECD to decrease in general. Interpreting the strength of the tendency is left to the reader’s judgment.