Interpretation of doubled-angle plots

摘要

The article by Kunert et al.1 should serve as a standardized template for authors and journals when reporting astigmatic outcomes. There is, however, one small error in the interpretation of the doubled-angle plots that we would like to clarify in view of our articles describing these methods. On page 761, column 2, of their article, Kunert et al. state that "[t]he ellipses of SD showed that there was slightly less variation in the y direction (superior-inferior) than in the x direction (nasal-temporal), but it was of the same order of magnitude." On a doubled-angle plot, the x-axis is not the "nasal-temporal" meridian and the y-axis is not the "superior-inferior" meridian as stated. As shown in our original figure of the doubled-angle plot (Figure 1), the radius of each ring has a constant magnitude, which is either positive or negative depending on the physical sign of the surgery. Negative is considered flattening or reducing the dioptric power in a meridian, and positive is steepening a meridian. In this case, the laser is removing a "smile" of tissue that flattens the steep meridian, so the physical equivalent is a negative sign for removal of tissue in any meridian.