title: Relationships between preoperative astigmatism and corneal optical power, axial length, intraocular pressure, gender, and patient age.
abstract: BACKGROUND
  Preoperative astigmatism is likely to influence the outcome of cataract surgery, but it is only rarely considered in studies of cataract surgery outcomes.
  
  
  METHODS
  As part of a population-based study of 5878 consecutive cataract surgeries performed from 1986 through 1990, I studied the relationship between preoperative astigmatism and corneal shape, axial length, intraocular pressure, gender, and age.
  
  
  RESULTS
  The men had more against-the-rule astigmatism than the women, and the preoperative astigmatism shifted for both genders toward against-the-rule with age. Long eyes tended to have more with-the-rule astigmatism. Also, astigmatism deviated more from normal in both long and short eyes, and the with-the-rule astigmatism decreased with increasing intraocular pressure. Finally, I found that a second-degree polynomial model better described the relation between the axial lengths and keratometric powers better than a linear one.
  
  
  CONCLUSIONS
  Axial length is related to the direction and amount of astigmatism. Because in the present study a second-degree polynomial described the relationship between the axial lengths and keratometric powers better than a simple linear regression, a polynomial model also probably should be used for calculating the power of the intraocular lens to be inserted.
authors.affiliation: Department of Ophthalmology, Lund University Hospital, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Ninn-Pedersen
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D001251:Astigmatism / Q000209:etiology*; D002387:Cataract Extraction; D003315:Cornea / Q000033:anatomy & histology*; D005123:Eye / Q000033:anatomy & histology*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012189:Retrospective Studies; D012737:Sex Factors; D014792:Visual Acuity