Peripapillary retinal nerve fiber layer thickness measurement by three-dimensional optical coherence tomography in a normal population

ABSTRACT

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 [OCTII]. 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. Mean peripapillary RNFL thickness measured by 3D-OCT [75.50 +/- 8.38] micro m was significantly less than that measured by OCT II [144.10 +/- 33.32 pn] [P<0.001]. Using 3D-OCT, 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]. 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