Abstract
Purpose: :
To investigate the relationship between retinal nerve fiber layer (RNFL) thickness measured by spectral-domain optical coherence tomography (OCT) and axial length in a sample of healthy eyes.
Methods: :
RNFL thickness was measured by CirrusTM HD-OCT in 39 eyes of 39 healthy subjects whose axial length was assessed by ultrasound biometry.
Results: :
Axial length ranged between 20.80 and 22.5mm in 11 eyes, between 22.51 and 25.0mm in 11 eyes and between 25.01 and 28.85 mm in 17 eyes. Analysis of variance showed a statistical difference (p=0.0016) among the 3 groups, whose average 360° RNFL thickness was respectively 102.63±12.33, 93.63±6.36 and 87.41±10.21 microns. Linear regression disclosed a statistically significant relationship between axial length and average 360° RNFL thickness (r=-0.6147, p<0.0001), superior quadrant (r=-0.4822, p=0.0019), nasal quadrant (r=-0.5918, p<0.0001) and inferior quadrant (r=-0.6409, p<0,0001), but not temporal quadrant (r=-0.07493, p>0.05).
Conclusions: :
Our data confirmed previous results obtained by time-domain OCT, as RNFL thickness measured by spectral-domain OCT is influenced by axial length. This phenomenon should be considered when interpreting a glaucoma suspect's Cirrus HD-OCT measurements compared with the normative database.
Keywords: optic nerve • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • nerve fiber layer