Polar value analysis of refractive data

PURPOSE: To demonstrate the use of polar value analysis of surgically induced astigmatism (SIA). SETTING: Department of Ophthalmology, Arhus University Hospital, Arhus, Denmark. METHODS: Univariate polar value analysis of SIA was demonstrated for a single patient and for aggregate data. Bivariate polar value analysis was performed for aggregate data. RESULTS: The meridional polar value AKP expresses the surgically induced flattening, while the oblique polar value AKP(+45) indicates the torque. This pair of polar values characterizes a regular astigmatism completely. In bivariate polar value analysis, the average SIA is the combined mean for AKP and AKP(+45), while the spread is a confidence area delineated by an ellipse. CONCLUSIONS: Univariate and bivariate polar value analyses, together with the surgically induced change in spherical equivalent power, yield an exact description of surgically induced change following refractive procedures.