title: Peripapillary retinal nerve fiber layer thickness measurement by three-dimensional optical coherence tomography in a normal population.
abstract: OBJECTIVE
  To determine peripapillary retinal nerve fiber layer (RNFL) thickness values by three-dimensional optical coherence tomography (3D-OCT) in a normal Iranian population and to evaluate the concordance of these measurements with those obtained by the second generation of optical coherence tomography (OCT II).
  
  
  METHODS
  In a cross-sectional observational study, 96 normal Iranian subjects 20-53 years old were enrolled. Peripapillary RNFL thickness in one randomly selected eye of each subject was measured by 3D-OCT and also by OCT II. Standard achromatic perimetry, corneal pachymetry and A-scan ultrasonographic biometry were also performed. Other study variables included age, gender, laterality (right versus left eye), refractive error, corneal diameter and disc area.
  
  
  RESULTS
  Mean peripapillary RNFL thickness measured by 3D-OCT (75.50±8.38) μm was significantly less than that measured by OCT II (144.10±33.32 μm) (P<0.001). Using 3DOCT, no significant difference in peripapillary RNFL thickness was observed by gender (P=0.90) or laterality (P=0.17); RNFL thickness had no correlation with age (P=0.95), axial length (P=0.32), spherical equivalent refractive error (P=0.21), central corneal thickness (P=0.66) and disc area (P=0.31). However, a positive correlation was found between peripapillary RNFL thickness and corneal diameter (P=0.03).
  
  
  CONCLUSIONS
  3D-OCT seems to yield lower RNFL thickness values as compared to OCT II. It seems advisable to obtain separate baseline measurements when using different generations of OCT machines.
authors: Labbafinejad Medical Center, Shahid Beheshti University, MC, Tehran, Iran.
authors: Mohammad
authors: M
authors: Pakravan
authors: Shila
authors: S
authors: Aramesh
authors: Shahin
authors: S
authors: Yazdani
authors: Mehdi
authors: M
authors: Yaseri
authors: Massih
authors: M
authors: Sedigh-Rahimabadi
keywords: Optical Coherence Tomography; Retinal Nerve Fiber Layer Thickness; Three-Dimensional Tomography