title: Axial Length/Corneal Radius of Curvature Ratio and Myopia in 3-Year-Old Children.
abstract: OBJECTIVE
  This study investigated the association of axial length (AL) to corneal radius of curvature (CRC) ratio with spherical equivalent (SE) in a 3-year old Asian cohort.
  
  
  METHODS
  Three-hundred forty-nine 3-year old Asian children from The Growing Up in Singapore towards Healthy Outcomes (GUSTO) birth cohort study underwent AL and CRC measurements with a noncontact ocular biometer and cycloplegic refraction using an autorefractor. The ratio of AL to CRC (AL/CRC) was calculated for all the participants, and subsequently AL, CRC, and AL/CRC were analyzed in relationship to SE.
  
  
  RESULTS
  The SE showed better correlation with AL/CRC (Spearman's correlation coefficient, ρ = -0.53; 95% confidence interval [CI]: -0.66; -0.49;P< 0.001) compared to either AL or CRC alone ([ρ = -0.36; 95% CI: -0.51 to 0.51;P= 0.01] and [ρ = 0.05; 95% CI: -0.04 to 0.17;P= 0.34], respectively). Mean AL/CRC was 2.91 ± 0.06 among myopes and decreased to 2.79 ± 0.06 among hyperopes. Axial length to corneal radius of curvature was strongly correlated with SE in myopes (ρ = -0.78; 95% CI: -3.76; -0.79;P= < 0.001), but not in emmetropes and hyperopes ([ρ = -0.39; 95% CI: -10.73; -0.57;P= 0.01] and [ρ = -0.18; 95% CI: -17.28; 12.42;P= 0.38], respectively). Linear regression adjusted for gender and ethnicity showed a 0.74-diopter shift in SE towards myopia with every 0.1 increase in AL/CRC ratio (P< 0.001,r2= 0.33).
  
  
  CONCLUSIONS
  The correlation between SE and AL/CRC is stronger than that between AL or CRC alone. This suggests that in a research setting, when cycloplegic refraction is difficult to perform on 3-year-old children, AL/CRC may be the next best reference for refractive error.
  
  
  CONCLUSIONS
  In the research setting, AL/CRC may be the next best reference for refractive error over AL alone when cycloplegic refraction is unavailable in 3-year old children.
authors.affiliation: Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Valencia Hui Xian
authors.initials: VH
authors.lastname: Foo
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.
authors.forename: Pavan Kumar
authors.initials: PK
authors.lastname: Verkicharla
authors.affiliation: Department of Ophthalmology, National University Hospital, National University Health System, Singapore, Singapore ; Memory Aging & Cognition Center, National University Health System, Singapore, Singapore.
authors.forename: Mohammad Kamran
authors.initials: MK
authors.lastname: Ikram
authors.affiliation: Saw Swee Hock School of Public Health, National University of Singapore, Singapore.
authors.forename: Sharon Yu Lin
authors.initials: SY
authors.lastname: Chua
authors.affiliation: Department of Obstetrics and Gynecology, National University Hospital, National University Health System, Singapore, Singapore.
authors.forename: Shirong
authors.initials: S
authors.lastname: Cai
authors.affiliation: Saw Swee Hock School of Public Health, National University of Singapore, Singapore.
authors.forename: Chuen Seng
authors.initials: CS
authors.lastname: Tan
authors.affiliation: Department of Obstetrics and Gynecology, National University Hospital, National University Health System, Singapore, Singapore ; Singapore Institute for Clinical Sciences - ASTAR, Singapore, Singapore.
authors.forename: Yap-Seng
authors.initials: YS
authors.lastname: Chong
authors.affiliation: KK Women's and Children's Hospital, Singapore, Singapore.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Kwek
authors.affiliation: Singapore Institute for Clinical Sciences - ASTAR, Singapore, Singapore ; Liggins Institute, University of Auckland, Auckland, New Zealand.
authors.forename: Peter
authors.initials: P
authors.lastname: Gluckman
authors.affiliation: Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore ; Department of Ophthalmology, National University Hospital, National University Health System, Singapore, Singapore.
authors.forename: Tien-Yin
authors.initials: TY
authors.lastname: Wong
authors.affiliation: Department of Ophthalmology, National University Hospital, National University Health System, Singapore, Singapore.
authors.forename: Cheryl
authors.initials: C
authors.lastname: Ngo
authors.affiliation: Saw Swee Hock School of Public Health, National University of Singapore, Singapore.
authors.forename: Seang-Mei
authors.initials: SM
authors.lastname: Saw
authors.affiliation: Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.lastname: On Behalf Of The Gusto Study Group
keywords: CRC ratio; myopia; axial length; cornea radius of curvature; AL