title: Distribution of the anterior, posterior, and total corneal astigmatism in healthy eyes.
abstract: OBJECTIVE
  To evaluate the magnitude and axis orientation of the anterior, posterior, and total corneal astigmatism in normal healthy eyes of an Iranian population.
  
  
  METHODS
  In a prospective cross-sectional study, ophthalmic and anterior segment parameters of 153 healthy eyes of 153 subjects were evaluated by Galilei dual Scheimpflug analyzer. The magnitude and axis orientation [with-the-rule (WTR), against-the-rule (ATR), and oblique] of the anterior, posterior, and total corneal astigmatism measurements (ACA, PCA, and TCA) were compared according to the age, sex, and other ophthalmic parameters.
  
  
  RESULTS
  The mean ± SD age of the study population was 30 ± 5.9 years. The mean magnitude was 1.09 ± 0.76 diopters (D) for ACA, 0.30 ± 0.13 D for PCA, and 1.08 ± 0.77 D for TCA. Males had a significantly higher magnitude of PCA than females (p = 0.041). Most eyes had a WTR anterior astigmatism and an ATR posterior astigmatism. The WTR astigmatism had a higher mean magnitude compared to the ATR and oblique astigmatism in all the astigmatism groups, with a significant difference in the ACA and TCA groups (p < 0.05). PCA magnitude exceeded 0.50 D in only 7.8% of the subjects. ACA, PCA, and TCA were significantly correlated with each other and also had a significant correlation with the anterior and posterior maximum corneal elevation measurements (p < 0.001).
  
  
  CONCLUSIONS
  The results of this study although are limited due to the small number of participants and confined to our demographics, provided information regarding a population that was not described before and may be helpful in obtaining optimum results in astigmatism correction in refractive surgery or designing new intraocular lenses.
authors.affiliation: Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Sepehr
authors.initials: S
authors.lastname: Feizi
authors.affiliation: Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Moh@Naderan.com.|Eye Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Qazvin Square, Tehran, 1336616351, Iran. Moh@Naderan.com.
authors.forename: Mohammad
authors.identifier: http://orcid.org/0000-0001-5774-4607
authors.initials: M
authors.lastname: Naderan
authors.affiliation: Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Vahid
authors.initials: V
authors.lastname: Ownagh
authors.affiliation: Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Sadeghpour
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000869:Anterior Eye Segment / Q000503:physiopathology; D001251:Astigmatism / Q000503:physiopathology*; D019781:Corneal Topography; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D057972:Posterior Eye Segment / Q000503:physiopathology; D011446:Prospective Studies; D012030:Refractive Errors / Q000503:physiopathology; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult
keywords: Anterior corneal astigmatism; Astigmatism; Dual Scheimpflug analyzer; Healthy eye; Posterior corneal astigmatism; Total corneal astigmatism