Novel Microsoft Excel spreadsheet calculator for vector analysis of mass astigmatism data and comparison between Alpins and Thibos methods

Abstract

Background Vector analysis is mandatory for reporting astigmatism and for the evaluation of different refractive procedures. Aim The aim of this study was to describe and evaluate a new spreadsheet calculator for vector analysis of mass astigmatism data and to compare between Alpins and Thibos methods. Patients and methods Using Microsoft Office Excel 2016, a new astigmatic calculator was designed, based on Alpins and Thibos methods of vector analysis. Mass astigmatic data input involved power in diopters and axis direction in degrees. The calculator was investigated on 20 eyes for which photorefractive keratectomy was performed. Preoperative and postoperative manifest refractions were measured. Comparisons were done between the results of Alpins and Thibos methods of analysis. Results The mean surgically induced astigmatism (SIA) was 2.547±0.721 D and the change in astigmatism power vector (ΔAPV) calculated with the Thibos method was 1.27±0.36 D. A perfect positive correlation (r=1; P<0.000) was present between SIA and ΔAPV with SIA=2ΔAPV. A perfect positive correlation (r=1; P<0.000) was also present between the index of success and APV ratio. Conclusion Vector analysis of mass astigmatism data could be performed using the new Excel calculator. Alpins and Thibos methods showed interchangeability between their results.

Keywords

• astigmatism
• excel
• vector analysis