title: Keratoconus: classification scheme based on videokeratography and clinical signs.
abstract: OBJECTIVE
  To determine in a longitudinal study whether there is correlation between videokeratography and clinical signs of keratoconus that might be useful to practicing clinicians.
  
  
  METHODS
  Cornea-Genetic Eye Institute, Cedars-Sinai Medical Center, Los Angeles, California, USA.
  
  
  METHODS
  Eyes grouped as keratoconus, early keratoconus, keratoconus suspect, or normal based on clinical signs and videokeratography were examined at baseline and followed for 1 to 8 years. Differences in quantitative videokeratography indices and the progression rate were evaluated. The quantitative indices were central keratometry (K), the inferior-superior (I-S) value, and the keratoconus percentage index (KISA). Discriminant analysis was used to estimate the classification rate using the indices.
  
  
  RESULTS
  There were significant differences at baseline between the normal, keratoconus-suspect, and early keratoconus groups in all indices; the respective means were central K: 44.17 D, 45.13 D, and 45.97 D; I-S: 0.57, 1.20, and 4.44; log(KISA): 2.49, 2.94, and 5.71 (all P<.001 after adjusting for covariates). Over a median follow-up of 4.1 years, approximately 28% in the keratoconus-suspect group progressed to early keratoconus or keratoconus and 75% in the early keratoconus group progressed to keratoconus. Using all 3 indices and age, 86.9% in the normal group, 75.3% in the early keratoconus group, and 44.6% in the keratoconus-suspect group could be classified, yielding a total classification rate of 68.9%.
  
  
  CONCLUSIONS
  Cross-sectional and longitudinal data showed significant differences between groups in the 3 indices. Use of this classification scheme might form a basis for detecting subclinical keratoconus.
authors.affiliation: Cornea-Genetic Eye Institute, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA.
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Li
authors.forename: Huiying
authors.initials: H
authors.lastname: Yang
authors.forename: Yaron S
authors.initials: YS
authors.lastname: Rabinowitz
mesh_terms: D000328:Adult; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007640:Keratoconus / Q000145:classification* / Q000175:diagnosis*; D008297:Male; D011446:Prospective Studies; D014741:Video Recording
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