title: Correlation of major components of ocular astigmatism in myopic patients.
abstract: OBJECTIVE
  To investigate the correlation of major components of ocular astigmatism in myopic patients in an academic hospital.
  
  
  METHODS
  This cross-sectional study was conducted on 376 eyes of 188 patients who were referred to Farabi Eye Hospital for refractive surgery. Preoperative examinations including refraction and corneal topography were performed for all candidates to measure refractive and corneal astigmatism. Ocular residual astigmatism was calculated using vector analysis. Pearson's correlation and ANOVA analysis were used to evaluate the strength of the association between different types of astigmatism. Both eyes were defined as cluster and the Generalized Estimating Equations (GEE) analysis were performed.
  
  
  RESULTS
  Mean age of 119 women (63.3%) and 69 men (36.7%) was 27.8 ± 5.7 years. Mean refractive error based on spherical equivalent was -3.59 ± 1.95D (range, -0.54 to -10.22D). Mean refractive and corneal astigmatism was 1.97 ± 1.3D and 1.85 ± 1.01D, respectively. Mean amount of ORA was 0.65 ± 0.36D.There was a significant correlation between ORA and refractive astigmatism(r=0.23, p<0.001), corneal and refractive astigmatism (r=0.91, p<0.001) and a weak correlation between ORA and corneal astigmatism (r=0.13, p=0.014). There was a significant correlation between J0 and J45 values of ORA and corneal astigmatism (p<0.001).
  
  
  CONCLUSIONS
  There is a significant correlation between ORA and refractive astigmatism, refractive and corneal astigmatism and a weak correlation between ORA and corneal astigmatism in refractive surgery candidates. Identifying the type of astigmatism and preoperative measurement of ocular residual astigmatism is highly recommended prior to any refractive surgery, especially in cases with significant astigmatism.
authors.affiliation: Associate Professor of Ophthalmology, Farabi Eye Hospital, Ophthalmology Department and Eye Research Center, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Mehrdad
authors.initials: M
authors.lastname: Mohammadpour
authors.affiliation: Researcher, Farabi Eye Hospital, Ophthalmology Department and Eye Research Center, Tehran University of Medical Sciences, Tehran, Iran. Electronic address: zahra.heidari77@Yahoo.com.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Heidari
authors.affiliation: Department of epidemiology, Faculty of health, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Khabazkhoob
authors.affiliation: Farabi Eye Hospital, Ophthalmology Department and Eye Research Center, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Afsaneh
authors.initials: A
authors.lastname: Amouzegar
authors.affiliation: Professor of Ophthalmology, Noor Eye Hospital, Noor Ophthalmology Research Center, Tehran, Iran.
authors.forename: Hassan
authors.initials: H
authors.lastname: Hashemi
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D019781:Corneal Topography; D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer / Q000627:therapeutic use; D008297:Male; D009216:Myopia / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D012029:Refraction, Ocular / Q000502:physiology*; D012189:Retrospective Studies; D014792:Visual Acuity
keywords: Corneal astigmatism; Correlation; Myopia; Ocular residual astigmatism; Refractive astigmatism