title: The effect of corneal anterior surface eccentricity on astigmatism after cataract surgery.
abstract: OBJECTIVE
  To evaluate the effect of cornea eccentricity on induced astigmatism after cataract surgery.
  
  
  METHODS
  The study included 125 eyes of 87 patients. Preoperative corneal astigmatism, pachymetry, and eccentricity were measured. During cataract surgery, the location of the main incision (2.8-mm clear corneal) was selected to be either superior, superior-nasal, superior-temporal, nasal, or temporal to decrease the preexisting corneal astigmatism. Aspheric intraocular lenses were implanted. Keratometry and manifest refraction were recorded 6 months after surgery. Astigmatism was calculated using vector subtraction software.
  
  
  RESULTS
  Three parameters significantly affected postoperative astigmatism: preoperative amount of corneal astigmatism, eccentricity of anterior cornea, and location of the main incision. The mean surgically induced astigmatism (SIA) was calculated to be: superior = 0.82 diopters (D), superior-nasal = 0.50 D, superior-temporal = 0.63 D, temporal = 0.45 D, and nasal = 0.55 D. Superior incision induced the greatest SIA and temporal incision induced the smallest SIA. The eccentricity of anterior cornea showed significantly positive correlation with the amount of SIA (P < .001). The preoperative corneal cylinder power showed significantly positive correlation with the amount of SIA (P < .001).
  
  
  CONCLUSIONS
  Postoperative astigmatism was affected by various factors in cataract surgery. The greatest postoperative astigmatism is expected in corneas with high anterior eccentricity, high preoperative corneal astigmatism, and superior location of the main incision.
authors.affiliation: Department of Ophthalmology, Dongguk University, Ilsan Hospital, Koyang, Kyunggido, South Korea. choulyong@yahoo.co.kr
authors.forename: Choul Yong
authors.initials: CY
authors.lastname: Park
authors.forename: Roy S
authors.initials: RS
authors.lastname: Chuck
authors.forename: Prabjot
authors.initials: P
authors.lastname: Channa
authors.forename: Chi-Yeon
authors.initials: CY
authors.lastname: Lim
authors.forename: Byung-Jin
authors.initials: BJ
authors.lastname: Ahn
mesh_terms: D000368:Aged; D001251:Astigmatism / Q000175:diagnosis* / Q000209:etiology / Q000517:prevention & control; D002387:Cataract Extraction / Q000009:adverse effects* / Q000379:methods; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010781:Photography; D011446:Prospective Studies; D012307:Risk Factors