title: Peripapillary retinal nerve fiber layer thickness in a population of 6-year-old children: findings by optical coherence tomography.
abstract: OBJECTIVE
  To study the distribution of retinal nerve fiber layer (RNFL) thickness by ocular and demographic variables in a population-based study of young children.
  
  
  METHODS
  Population-based cross-sectional study.
  
  
  METHODS
  One thousand seven hundred sixty-five of 2238 (78.9%) eligible 6-year-old children participated in the Sydney Childhood Eye Study between 2003 and 2004. Mean age was 6.7 years (50.9% boys).
  
  
  METHODS
  Detailed examination included cycloplegic autorefraction and measurement of axial length. Retinal nerve fiber layer scans using an optical coherence tomographer were performed with a circular scan pattern of 3.4-mm diameter. Multivariate analyses were performed to examine the distribution of RNFL parameters with gender, ethnicity, axial length, and refraction.
  
  
  METHODS
  Peripapillary RNFL thickness and RNFL(estimated integral) (RNFL(EI)), which measures the total cross-sectional area of ganglion cell axons converging onto the optic nerve head.
  
  
  RESULTS
  Peripapillary RNFL thickness and RNFL(EI) were normally distributed. The mean+/-standard deviation RNFL average thickness was 103.7+/-11.4 microm and RNFL(EI) was 1.05+/-0.12 mm2. Retinal nerve fiber layer thickness was least for the temporal quadrant (75.7+/-14.7 microm), followed by the nasal (81.7+/-19.6 microm), inferior (127.8+/-20.5 microm), and superior (129.5+/-20.6 microm) quadrants. Multivariate adjusted RNFL average thickness was marginally greater in boys than in girls (104.7 microm vs. 103.2 microm; P = 0.007) and in East Asian than in white children (107.7 microm vs. 102.7 microm; P<0.0001). The RNFL was thinner with greater axial length (P(trend)<0.0001) and less positive spherical equivalent refractions (P(trend) = 0.004).
  
  
  CONCLUSIONS
  Retinal nerve fiber layer average thickness and RNFL(EI) followed a normal distribution. Retinal nerve fiber layer thickness varied marginally with gender, but differences were more marked between white and East Asian children. Retinal nerve fiber layer thinning was associated with increasing axial length and less positive refractions.
authors.affiliation: Centre for Vision Research, Department of Ophthalmology, University of Sydney, and Westmead Millennium Institute, Sydney, Australia.
authors.forename: Son C
authors.initials: SC
authors.lastname: Huynh
authors.forename: Xiu Ying
authors.initials: XY
authors.lastname: Wang
authors.forename: Elena
authors.initials: E
authors.lastname: Rochtchina
authors.forename: Paul
authors.initials: P
authors.lastname: Mitchell
mesh_terms: D000886:Anthropometry; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D009412:Nerve Fibers; D016011:Normal Distribution; D009900:Optic Nerve / Q000033:anatomy & histology*; D012029:Refraction, Ocular / Q000502:physiology; D012165:Retinal Ganglion Cells / Q000166:cytology*; D041623:Tomography, Optical Coherence / Q000379:methods*