title: Analysis of surgically induced astigmatism on the posterior surface of the cornea.
abstract: OBJECTIVE
  To measure surgically induced astigmatism (SIA) on the posterior surface of the cornea using Scheimpflug-based keratometry on eyes with with-the-rule astigmatism.
  
  
  METHODS
  Repeated Scheimpflug-based keratometry was obtained preoperatively and a mean of 8.65 weeks postoperatively following superior clear corneal incisions. Differences in the keratometric values and SIA were determined on the anterior and posterior surfaces separately and the data were analyzed.
  
  
  RESULTS
  The study included 88 eyes of 88 patients (age range: 46.4 to 87.5 years), with the steepest total corneal meridian between 75° and 105°. Preoperatively, the magnitude of the anterior and posterior corneal astigmatism was 0.74 ± 0.44 and 0.29 ± 0.14 diopters (D), respectively, which was greater than 0.5 D in 10 eyes (11.36%). The difference between preoperative and postoperative keratometric data on the posterior surface was significant, as was the difference between the preoperative and postoperative posterior astigmatism. The mean magnitude of posterior corneal SIA was 0.32 ± 0.29 D, which was 0.5 D or greater in 22 eyes (25.00%). A statistically significant correlation was observed between the diopter of the preoperatively measured posterior corneal astigmatism and the postoperative SIA on the posterior surface (r = 0.34, P = .001). The correlation was not significant between SIA on the anterior and posterior surfaces (r = 0.10, P = .36).
  
  
  CONCLUSIONS
  SIA on the posterior surface of the cornea may have a significant role, especially in cases of toric intraocular lens implantation. Posterior corneal astigmatism and SIA may have a significant clinical impact on more precise planning of cataract surgeries.
authors: Gabor
authors: G
authors: Nemeth
authors: Andras
authors: A
authors: Berta
authors: Eszter
authors: E
authors: Szalai
authors: Ziad
authors: Z
authors: Hassan
authors: Laszlo
authors: L
authors: Modis
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000209:etiology* / Q000503:physiopathology*; D002386:Cataract / Q000150:complications; D003315:Cornea / Q000503:physiopathology* / Q000601:surgery; D063171:Corneal Pachymetry; D019781:Corneal Topography; D006801:Humans; D019654:Lens Implantation, Intraocular; D008875:Middle Aged; D018918:Phacoemulsification / Q000009:adverse effects* / Q000379:methods