title: Evaluation of posterior astigmatism measured with Scheimpflug imaging.
abstract: OBJECTIVE
  Our aim was to assess the corneal power, axis, and age dependence of the anterior and posterior corneal surfaces with Scheimpflug imaging.
  
  
  METHODS
  Patients older than 10 years without a history of ocular surgery, corneal diseases, contact lens wearing, or severe dry eye were enrolled. Data regarding the anterior and posterior cornea were analyzed by means of Scheimpflug imaging (Pentacam HR).
  
  
  RESULTS
  The median age was 46.8 years (range: 10.0-90.3), and involved 827 eyes of 827 patients. Posterior corneal astigmatism was a median of -0.30 diopters (D) and exceeded 0.50 D in 12.56%. The ratio of the anterior-to-posterior corneal radius was a median of 1.217 (range: 1.021-1.402). The correlation between this ratio and age was significant (r = -0.219; P < 0.001). The correlation between anterior and posterior corneal astigmatism and age was significant. At the anterior surface, the ratio of with-the-rule astigmatism was 80.0% for the age range 10 to 20, decreasing to 36.0% for those aged over 81 years, whereas the ratio of against-the-rule astigmatism increased from 7.1% to 44.0%. At the posterior surface, the ratio of with-the-rule astigmatism was 94.3% for the age range 10 to 20 years, decreasing to 84.0% for those aged over 81 years, whereas the ratio of against-the-rule astigmatism increased from 1.4% to 8.0%.
  
  
  CONCLUSIONS
  The posterior cornea significantly influences corneal astigmatism. Its power value and orientation are much more stable with advancing age compared with anterior surface values.
authors.affiliation: *Department of Ophthalmology, University of Debrecen, Debrecen, Hungary; and †Orbi-Dent Refractive Surgery and Medical Center, Debrecen, Hungary.
authors.forename: Gabor
authors.initials: G
authors.lastname: Nemeth
authors.forename: Andras
authors.initials: A
authors.lastname: Berta
authors.forename: Agnes
authors.initials: A
authors.lastname: Lipecz
authors.forename: Ziad
authors.initials: Z
authors.lastname: Hassan
authors.forename: Eszter
authors.initials: E
authors.lastname: Szalai
authors.forename: Laszlo
authors.initials: L
authors.lastname: Modis
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D001251:Astigmatism / Q000175:diagnosis*; D002648:Child; D003315:Cornea / Q000473:pathology*; D063171:Corneal Pachymetry; D003952:Diagnostic Imaging / Q000379:methods*; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged