title: Influence of disc area on retinal nerve fiber layer thickness measurement by spectral domain optical coherence tomography.
abstract: BACKGROUND
  To examine the effect of optic disc area on peripapillary RNFLT (retinal nerve fiber layer thickness) measurement at circle diameter of 3.4 mm around optic nerve head using spectral OCT/SLO (Optical coherence tomography/scanning laser ophthalmoscope).
  
  
  METHODS
  In this prospective, cross sectional study, one hundred and two eyes of 102 normal subjects underwent RNFLT and disc area measurement using spectral OCT/SLO. Based on disc area, subjects were divided into three groups i.e., <3 mm2 (32 eyes), 3-4 mm2 (36 eyes) and >4 mm2 (34 eyes). The effect of disc area on RNFLT parameters was analyzed using linear regression analysis.
  
  
  RESULTS
  The mean and quadrant RNFLT did not show significant correlation with disc area in subjects with disc area of <4 mm2, however in eyes with disc area >4 mm2, average RNFLT, superior and temporal quadrant RNFLT showed negative correlation with disc area, which was statistically significant (P = 0.004, P = 0.005 and P = 0.002, respectively).
  
  
  CONCLUSIONS
  In healthy eyes of disc area <4 mm2, disc size does not appear to affect peripapillary RNFLT measurement by spectral OCT/SLO. Average, superior and temporal quadrant RNFLT measurements were inversely proportional to disc area in eyes with disc area >4 mm2. Hence, RNFLT measurement by OCT in eyes with optic disc area of >4 mm2 should be interpreted carefully.
authors.affiliation: Department of Glaucoma, Vasan Eye Care, 8-1-5/7, Janak Plaza, Opp Clock Tower, SD Road, Secunderabad, Andhra Pradesh, India.
authors.forename: Tarannum
authors.initials: T
authors.lastname: Mansoori
authors.forename: Nagalla
authors.initials: N
authors.lastname: Balakrishna
authors.forename: Kalluri
authors.initials: K
authors.lastname: Viswanath
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D005901:Glaucoma / Q000175:diagnosis*; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009898:Optic Disk / Q000473:pathology*; D011446:Prospective Studies; D015203:Reproducibility of Results; D012165:Retinal Ganglion Cells / Q000473:pathology*; D041623:Tomography, Optical Coherence / Q000379:methods*; D055815:Young Adult