title: Value of posterior keratometry in the assessment of surgically induced astigmatic change in cataract surgery.
abstract: OBJECTIVE
  To investigate the value of posterior keratometry in the assessment of surgically induced astigmatic change (AC) in cataract surgery, with particular emphasis on the influence of test-retest variability.
  
  
  METHODS
  Seventy-seven eyes of 77 cataract patients scheduled for routine cataract surgery were enrolled. All patients received a 2.2-mm self-sealing scleral incision (n = 24), single-plane clear corneal incision (SPCCI; n = 29) or biplanar clear corneal incision (BPCCI; n = 24). Measurements of anterior and posterior corneal astigmatism were performed with a rotating Scheimpflug camera (Pentacam HR) preoperatively and postoperatively. Two repeated readings were taken preoperatively to assess the role of the test-retest effect. Astigmatic change (AC) was analysed according to the polar value method.
  
  
  RESULTS
  On the anterior corneal surface, SPCCIs and BPCCIs caused a statistically significant mean flattening of the incisional meridian of 0.37 and 0.27 dioptres (D), respectively. Scleral incisions on average did not cause AC, although steepening, flattening or torque beyond the test-retest effect was observed in individual cases. On the posterior surface, mean power changes in the incisional meridian were below 0.1 D for all incisions, and these changes were of the same order of magnitude as the test-retest effect.
  
  
  CONCLUSIONS
  Surgically induced AC of the posterior corneal surface after cataract surgery is of negligible clinical relevance. Moreover, it is of the same order of magnitude as the test-retest variability of the measurement device and therefore cannot (yet) be reliably assessed.
authors.affiliation: Rotterdam Ophthalmic Institute, Rotterdam, The Netherlands.
authors.forename: Stijn
authors.initials: S
authors.lastname: Klijn
authors.affiliation: Rotterdam Ophthalmic Institute, Rotterdam, The Netherlands.
authors.forename: Charlotte M
authors.initials: CM
authors.lastname: van der Sommen
authors.affiliation: Rotterdam Ophthalmic Institute, Rotterdam, The Netherlands.
authors.forename: Victor Arni D P
authors.initials: VA
authors.lastname: Sicam
authors.affiliation: Rotterdam Ophthalmic Institute, Rotterdam, The Netherlands.|Department of Ophthalmology, Amphia Hospital, Breda, The Netherlands.
authors.forename: Nicolaas J
authors.initials: NJ
authors.lastname: Reus
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000175:diagnosis*; D003315:Cornea / Q000473:pathology* / Q000601:surgery; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D005260:Female; D006801:Humans; D007049:Iatrogenic Disease; D019654:Lens Implantation, Intraocular; D008297:Male; D008875:Middle Aged; D018918:Phacoemulsification; D010781:Photography / Q000379:methods*; D011446:Prospective Studies; D012590:Sclera / Q000601:surgery
keywords: Scheimpflug; posterior corneal surface; posterior keratometry; surgically induced astigmatic change; surgically induced astigmatism; test-retest variability