title: The optic nerve head assessed with HRT in 5-16-year-old normal children: normal values, repeatability and interocular difference.
abstract: OBJECTIVE
  To investigate the normal values, repeatability and interocular difference of the optic nerve head, using Heidelberg retina tomography (HRT), in 5-16-year-old full-term children with normal birth weights.
  
  
  METHODS
  Fifty-six children with normal visual acuity and refraction were examined with HRT-II/III. Three examinations were performed on each eye. One eye was randomized for analyses of normal values and repeatability, and 54 eyes could be evaluated. The coefficient of variance and the intraclass correlation (ICC) were calculated, and the ISNT rule was noted. The correlation between right and left eyes and the limits of difference were determined in 50 pair of eyes.
  
  
  RESULTS
  The mean values of disc and rim areas were 2.16 (SD 0.47) and 1.75 (SD 0.39) mm(2) respectively. The coefficients of variance varied between optic nerve parameters from 1.8% to 21%, and the ICCs were >0.88. All parameters except retinal nerve fibre layer thickness correlated with the disc area. The ISNT rule was fulfilled in 56% of the eyes. The interocular difference was large but not statistically significant.
  
  
  CONCLUSIONS
  We conclude that HRT can be used in children between 5 and 16 years of age, and normal values presented in the study can be used for comparison of children with optic nerve diseases. Because the assessment of rim area varied the least, it may be the parameter to use for follow-up. The normal large interocular difference should be taken into account when comparing eyes in the individual child.
authors.affiliation: Department of Ophthalmology, Uppsala University Hospital, Uppsala, Sweden. eva.larsson@neuro.uu.se
authors.forename: Eva
authors.initials: E
authors.lastname: Larsson
authors.forename: Eva
authors.initials: E
authors.lastname: Nuija
authors.forename: Albert
authors.initials: A
authors.lastname: Alm
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D054023:Lasers, Semiconductor; D008297:Male; D009887:Ophthalmoscopy / Q000379:methods*; D009898:Optic Disk / Q000033:anatomy & histology*; D012016:Reference Values; D015203:Reproducibility of Results; D014054:Tomography; D014792:Visual Acuity / Q000502:physiology