title: The effect of pterygium on corneal astigmatism.
abstract: OBJECTIVE
  To determine the effect of pterygium on corneal astigmatism.
  
  
  METHODS
  Two hundred and forty three eyes of 173 patients with primary pterygium were included in the present study. The extension of pterygium was measured by slit lamp and corneal astigmatism was measured by corneal topography. Correlation of the data was discussed.
  
  
  RESULTS
  The size of pterygium extended from 0.50 mm to 8.10 mm (2.11 +/- 1.10). The diopter of corneal astigmatism ranged from 0.10 diopter to 14.60 diopter (1.86 +/- 2.39). The axis of corneal astigmatism was found in vertical axis 156 eyes (64.2%), oblique axis 36 eyes (14.8%) and horizontal axis 51 eyes (21.0%). The degree of corneal astigmatism significantly correlated with the extension of pterygium on the cornea (R Square = 0.45, p < 0.001). When the extension of pterygium exceeded 2.25 mm, there was a chance of developing corneal astigmatism of 2 diopter or more (86.21% of sensitivity and 80% of specificity).
  
  
  CONCLUSIONS
  The extension of pterygium is significantly correlated with the degree of corneal astigmatism in the positive direction, with the highest percentage of with-the-rule astigmatism. Pterygium exceeding 2.25 mm of length should be considered within the limits of surgery.
authors.affiliation: Ophthalmology Division, Department of Clinical Science, Faculty of Medicine, Thammasat University, Rangsit Campus, Pathum Thani 12120, Thailand.
authors.forename: Kosol
authors.initials: K
authors.lastname: Kampitak
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D001251:Astigmatism / Q000175:diagnosis / Q000453:epidemiology*; D015331:Cohort Studies; D015897:Comorbidity; D019781:Corneal Topography; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011336:Probability; D011446:Prospective Studies; D011625:Pterygium / Q000175:diagnosis / Q000453:epidemiology*; D012372:ROC Curve; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D017678:Sex Distribution; D013785:Thailand / Q000453:epidemiology