Evaluation of anterior, posterior, and total corneal astigmatism in normal subjects

Abstract

Background: The aim of this study was to evaluate the magnitude and axis orientation of anterior, posterior, and total corneal astigmatism (ACA, PCA, and TCA, respectively). Methods: In this retrospective study, pentacam topographical maps of 226 eyes (113 patients) with 1.0 to 6.0 diopters (D) of astigmatism were analyzed. Topographical anterior and posterior corneal surface astigmatism was determined. The magnitude and axis orientation of the anterior, posterior and total corneal astigmatism were compared. Findings: The mean age of the study population was 33.00 ± 6.74 years. The mean magnitude was 2.02 ± 0.99, 0.44 ± 0.20, and 1.98 ± 1.01 diopters for anterior, posterior, and total corneal astigmatism, respectively. Most eyes had with-the-rule (WTR) anterior astigmatism and against-the-rule (ATR) posterior astigmatism. With-the-rule astigmatism had a higher mean magnitude compared to against-the-rule and oblique astigmatism in anterior and posterior corneal astigmatism groups. Posterior corneal astigmatism magnitude exceeded 0.75 diopters in only 8 of the subjects. Anterior corneal astigmatism had a significant positive correlation with posterior and total corneal astigmatism (P < 0.001 for both, r = 0.83 and 0.98, respectively). Moreover, posterior corneal astigmatism had a significant positive correlation with total corneal astigmatism (P < 0.001, r = 0.78). Conclusion: The provided information of this study may be helpful in obtaining optimum results in astigmatism correction in refractive surgery or designing new intraocular lenses. © Isfahan University of Medical Sciences(IUMS), 2017. All Rights Resreved.