title: Predictors of normal optic nerve head, retinal nerve fiber layer, and macular parameters measured by spectral domain optical coherence tomography.
abstract: OBJECTIVE
  To evaluate the effects of signal strength, age, sex, optic disc size, and axial length on the normal optic nerve head (ONH), retinal nerve fiber layer (RNFL), and macular measurements with spectral domain optical coherence tomography (SD-OCT).
  
  
  METHODS
  In an observational, cross-sectional study, 119 eyes of 60 normal subjects of Indian origin underwent ONH, RNFL, and macular imaging with SD-OCT during the same visit. Linear mixed-modeling methods were used to evaluate the effects of signal strength, age, sex, optic disc area, and axial length on ONH, RNFL, and macular measurements.
  
  
  RESULTS
  ONH rim measurements increased and cup measurements decreased with increasing signal strengths. For a 10-unit increase in signal strength, total rim area increased by a mean of 0.1 mm(2). ONH measurements also increased with increasing optic disc size. Rim measurements decreased and cup measurements increased with increasing axial length. None of the predictors influenced RNFL measurements. Macular inner retinal thickness decreased by a mean of 1.7 μm and macular full retinal thickness decreased by an average of 3.4 μm for every decade's increase in age. Sex did not influence any of the measurements.
  
  
  CONCLUSIONS
  Signal strength, optic disc size, and axial length had a significant effect on ONH measurements, whereas age had a significant effect on macular measurements. None of the predictors evaluated influenced the RNFL measurements. These predictors should be considered when evaluating change in the structural measurements in glaucoma over time.
authors.affiliation: VST Glaucoma Center, L. V. Prasad Eye Institute, Banjara Hills, Hyderabad, 500034, India. harshabl.76@gmail.com
authors.forename: Harsha L
authors.initials: HL
authors.lastname: Rao
authors.forename: Addepalli U
authors.initials: AU
authors.lastname: Kumar
authors.forename: Jonnadula G
authors.initials: JG
authors.lastname: Babu
authors.forename: Anjul
authors.initials: A
authors.lastname: Kumar
authors.forename: Sirisha
authors.initials: S
authors.lastname: Senthil
authors.forename: Chandra S
authors.initials: CS
authors.lastname: Garudadri
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008266:Macula Lutea / Q000033:anatomy & histology*; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers; D009898:Optic Disk / Q000033:anatomy & histology*; D012016:Reference Values; D012165:Retinal Ganglion Cells / Q000166:cytology*; D012737:Sex Factors; D041623:Tomography, Optical Coherence; D055815:Young Adult