title: Heidelberg retinal tomography of optic disc and nerve fiber layer in singapore children: variations with disc tilt and refractive error.
abstract: OBJECTIVE
  To evaluate the relationships in Singapore school children between optic nerve head parameters and retinal nerve fiber layer thickness images by using the Heidelberg Retinal Tomograph (HRT; Heidelberg Engineering, Heidelberg, Germany) and determining optic disc tilt and refractive error.
  
  
  METHODS
  This was a cross-sectional study involving 316 children 11 and 12 years of age (163 girls and 153 boys) selected randomly from one of the three schools in the Singapore Cohort study of Myopia. A total of 13 optic disc parameters were obtained from HRT images acquired before cycloplegia. Refractive errors were measured by cycloplegic autorefraction. The presence of optic disc tilt or otherwise was determined by two independent assessors using stereoscopic viewing of retinal photographs.
  
  
  RESULTS
  Of the 316 children, 142 had tilted discs. The tilting of optic discs was associated with a smaller disc, rim or cup area measurements, cup-to-disc area ratios, cup volumes or cup depths, but with a larger measured rim volume, rim-to-disc area ratios, height variation of the contour, retinal nerve fiber layer thicknesses or volumes, and a more negative cup shape measure (all P < 0.001). Decreased maximum cup depths were significantly associated with longer axial lengths (P < 0.001), but were not associated with spherical equivalent (P = 0.693). These associations remained only in children without tilted discs, but were no longer significant in those with tilted discs. Other HRT parameters were not associated with axial lengths or myopic status.
  
  
  CONCLUSIONS
  Optic nerve head parameters and retinal nerve fiber layer thickness measured by the current HRT algorithms are strongly influenced by the tilting of the optic nerve head, but not by refractive errors or axial length.
authors.affiliation: Singapore National Eye Center, Singapore. louistong@hotmail.com
authors.forename: Louis
authors.initials: L
authors.lastname: Tong
authors.forename: Yiong-Huak
authors.initials: YH
authors.lastname: Chan
authors.forename: Gus
authors.initials: G
authors.lastname: Gazzard
authors.forename: Seng-Chee
authors.initials: SC
authors.lastname: Loon
authors.forename: Allan
authors.initials: A
authors.lastname: Fong
authors.forename: Prabakaran
authors.initials: P
authors.lastname: Selvaraj
authors.forename: Paul R
authors.initials: PR
authors.lastname: Healey
authors.forename: Donald
authors.initials: D
authors.lastname: Tan
authors.forename: Tien Yin
authors.initials: TY
authors.lastname: Wong
authors.forename: Seang Mei
authors.initials: SM
authors.lastname: Saw
mesh_terms: D002648:Child; D003430:Cross-Sectional Studies; D003519:Cyclopentolate / Q000008:administration & dosage; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D008297:Male; D009184:Mydriatics / Q000008:administration & dosage; D009412:Nerve Fibers / Q000473:pathology*; D009898:Optic Disk / Q000002:abnormalities*; D010781:Photography; D011680:Pupil / Q000187:drug effects; D012029:Refraction, Ocular; D012030:Refractive Errors / Q000150:complications*; D012165:Retinal Ganglion Cells / Q000473:pathology*; D012846:Singapore; D014054:Tomography / Q000379:methods
chemical_list: D009184:Mydriatics; D003519:Cyclopentolate