Peripapillary Retinal Nerve Fiber Layer ThicknessMeasurement by Three-Dimensional OpticalCoherence Tomography in a Normal Population

Purpose: to determine peripapillary retinal nerve fiber layer (rnfl) thickness valuesby three-dimensional optical coherence tomography (3d-oct) in a normal iranianpopulation and to evaluate the concordance of these measurements with those obtainedby the second generation of optical coherence tomography (oct ii).methods: in a cross-sectional observational study, 96 normal iranian subjects 20-53years old were enrolled. peripapillary rnfl thickness in one randomly selected eye ofeach subject was measured by 3d-oct and also by oct ii. standard achromaticperimetry, 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) ìm was significantly less than that measured by oct ii (144.10±33.32 ìm) (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 cornealthickness (p=0.66) and disc area (p=0.31). however, a positive correlation was foundbetween peripapillary rnfl thickness and corneal diameter (p=0.03).conclusion: 3d-oct seems to yield lower rnfl thickness values as compared to octii. it seems advisable to obtain separate baseline measurements when using differentgenerations of oct machines.