title: Longitudinal changes in corneal curvature and its relationship to axial length in the Correction of Myopia Evaluation Trial (COMET) cohort.
abstract: OBJECTIVE
  To describe longitudinal changes in corneal curvature (CC) and axial length (AL) over 14 years, and to explore the relationship between AL and CC, and the axial length/corneal radius (AL/CR) ratio.
  
  
  METHODS
  In total 469, 6 to <12-year-old, children were enrolled in COMET. Measurements of refractive error, CC (D), CR (mm), and ocular component dimensions including AL were gathered annually. Linear mixed models were used to evaluate longitudinal changes adjusting for covariates (gender, ethnicity, lens type, baseline age and baseline refraction). The Pearson correlation coefficient between AL and CC was computed at each visit.
  
  
  RESULTS
  There was a slight but significant (p<0.0001) flattening in CC over 14 years. At all visits females had significantly steeper CC than males (overall difference=0.53 D, p<0.0001). Caucasians had the steepest CC, and Hispanics the flattest (p=0.001). The correlation between AL and CC was -0.70 (p<0.0001) at baseline (mean age=9.3 years) and decreased to -0.53 (p<0.0001) at the 14-year visit (mean age=24.1 years). The average AL/CR ratio was 3.15 at baseline and increased to 3.31 at the 14-year visit. The correlation between the magnitude of myopia and AL/CR ratio was significantly higher (p<0.0001) at each visit than the correlation between myopia and AL alone.
  
  
  CONCLUSIONS
  Differences in average corneal curvature by age, gender, and ethnicity observed in early childhood remain consistent as myopia progresses and stabilizes. This study also demonstrates increases in the AL/CR ratio as myopia progresses and then stabilizes, supporting observations from previous cross-sectional data.
authors.affiliation: Pennsylvania College of Optometry at Salus University, 8360 Old York Rd, Elkins Park, PA 19027, United States. Electronic address: mscheiman@salus.edu.
authors.forename: Mitchell
authors.initials: M
authors.lastname: Scheiman
authors.affiliation: Pennsylvania College of Optometry at Salus University, 8360 Old York Rd, Elkins Park, PA 19027, United States.
authors.forename: Jane
authors.initials: J
authors.lastname: Gwiazda
authors.affiliation: Pennsylvania College of Optometry at Salus University, 8360 Old York Rd, Elkins Park, PA 19027, United States.
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Pennsylvania College of Optometry at Salus University, 8360 Old York Rd, Elkins Park, PA 19027, United States.
authors.forename: Li
authors.initials: L
authors.lastname: Deng
authors.affiliation: Pennsylvania College of Optometry at Salus University, 8360 Old York Rd, Elkins Park, PA 19027, United States.
authors.forename: Karen
authors.initials: K
authors.lastname: Fern
authors.affiliation: Pennsylvania College of Optometry at Salus University, 8360 Old York Rd, Elkins Park, PA 19027, United States.
authors.forename: Ruth E
authors.initials: RE
authors.lastname: Manny
authors.affiliation: Pennsylvania College of Optometry at Salus University, 8360 Old York Rd, Elkins Park, PA 19027, United States.
authors.forename: Erik
authors.initials: E
authors.lastname: Weissberg
authors.affiliation: Pennsylvania College of Optometry at Salus University, 8360 Old York Rd, Elkins Park, PA 19027, United States.
authors.forename: Leslie
authors.initials: L
authors.lastname: Hyman
mesh_terms: D058452:Axial Length, Eye / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D003315:Cornea / Q000503:physiopathology*; D019781:Corneal Topography; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005139:Eyeglasses; D005260:Female; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D008297:Male; D009216:Myopia / Q000503:physiopathology / Q000628:therapy; D012029:Refraction, Ocular / Q000502:physiology; D014787:Vision Tests
keywords: AL/CR ratio; Axial length; Corneal curvature; Corneal radius; Curvatura de la córnea; Estudio sobre miopía COMET; Longitud axial; Myopia COMET study; Radio de la córnea; Ratio LA/RC