title: Correlation between pterygium size and induced corneal astigmatism.
abstract: OBJECTIVE
  Before invasion of the visual axis, pterygia typically induce with-the-rule astigmatism, which can be visually significant. In this study, we attempted to assess the quantitative relation between pterygium size and induced corneal astigmatism using corneal topography and digital imaging.
  
  
  METHODS
  Thirty-three eyes of 25 patients with primary pterygia were evaluated using corneal topography (TMS), slit-lamp photography, and digital imaging to correlate parameters of pterygium size with induced corneal astigmatism at the 3- and 6-mm optical zones.
  
  
  RESULTS
  Pterygia induce asymmetric with-the-rule astigmatism. Lesions extending >45% of the corneal radius or within 3.2 mm of the visual axis produce increasing degrees of induced astigmatism.
  
  
  CONCLUSIONS
  Once pterygia reach a critical size, they induce visually significant central with-the-rule astigmatic changes that may not be apparent by subjective refraction. This finding helps to identify those patients who may benefit from surgical intervention.
authors.affiliation: Department of Ophthalmology, University of Florida College of Medicine, Gainesville 32610-0284, USA.
authors.forename: A
authors.initials: A
authors.lastname: Lin
authors.forename: G
authors.initials: G
authors.lastname: Stern
mesh_terms: D001251:Astigmatism / Q000209:etiology / Q000473:pathology*; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D006801:Humans; D011625:Pterygium / Q000150:complications / Q000473:pathology*; D012029:Refraction, Ocular; D012189:Retrospective Studies; D014792:Visual Acuity