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In Reply.
—We thank Drs Hong and Shin for their observations. The equation for the regression line that relates rim area to disc area was indeed given incorrectly and should be as follows: Rim area = 0.58 × disc area + 0.15 mm2. The data shown in Fig 3, as well as the correlation coefficient and associated P value for the linear regression, remain unchanged. We regret this error.The depth determinations made by the Rodenstock analyzer are completely objective, with no operator input. We have found that in the vast majority of cases, small changes in the placement of the disc margin by the operator have no effect on the calculated cup volume. There may be some software differences between Drs Hong and Shin's apparatus and ours that account for the apparent discrepancy.We could not agree more with the last comment made by Drs Hong and Shin.