Study on the Validity of Novel Microsoft Excel Software for Calculating Surgically Induced Astigmatism

Purpose: The study was aimed to investigate the validity and predictability of a new software
calculator for surgically induced astigmatism quantification.
Techniques and Methods: Anew astigmatic calculator was designed, based on the Pythagorean
principle and trigonometric functions using Microsoft office excel 2007. The astigmatic magnitude was
quantified in diopters and axis direction was depicted in degrees. A calculator was applied,
investigated, and analyzed on 30 pseudophakic eyes that underwent temporal scleral incision surgery
within the bag intraocular lens implantation. Pre and postoperative anterior corneal curvature were
measured with Bausch and Lomb keratometer. Similarities and differences were compared with the
existing version 1.1 and 2.1 calculators and statistical analysis were performed using Microsoft excel.
Results: Mean pre and postoperative astigmatic magnitude were calculated as 62.67 (+/- 2.40) and
62.83 (+/- 2.29) diopters. The mean pre and postoperative astigmatic axes were 89.74 (+/- 1.37) and
89.51 (+/- 1.37) degrees. Pearson’s coefficient (r) was calculated as 0.91 and 0.83; the coefficient of
determinations (R2) was calculated as 0.82 and 0.68 for astigmatic magnitudes and axes respectively.
The student chi-square test was used to calculate T values, which were 0.39 and 0.26 for astigmatic
magnitude and axis respectively. A P-value of less than 0.05 was considered as statistically significant
(p 0.16). Validity was compared with existing surgically induced astigmatism calculators 1.1 and 2.1
versions and predictability was assessed by y=2.83+0.95x for astigmatic magnitude and
y=15.28+0.83x equations for astigmatic axis.
Conclusion: Present Microsoft excel calculator application was valid as the values for astigmatic
magnitude and axis were comparable with existing SIA calculators and can be used for astigmatic
predictability.Ophthalmic surgeons with fair knowledge concerning Microsoft office excel software
2007 are sufficient to enter their patients' pre and post-operative keratometric readings for appraising
surgically induced astigmatic quantifications and provide maximum postoperative visual rehabilitation
with prescription of the minimum amount of induced astigmatic error.