Ocular axial length influence on peripapillary retinal nerve fiber layer thickness measurement with optical coherence tomography

Background: Optical coherence tomography (OCT) allows the measurement of the peripapillary optic nerve fiber layer (RNFL) thickness. The effect of ocular axial length (AL) on RNFL thickness measurement may be relevant in the interpretation of OCT results in diagnosing optic nerve diseases.

Purpose: To assess the influence of ocular AL on RNFL thickness and on optic disc topographic parameters (optic disc area, rim area and cup volume) measured by OCT, in healthy individuals.

Methods: A sample of 109 healthy eyes classified into 3 groups according to AL (A: AL<22mm; B: AL 22-24.5mm; C: AL>24.5mm) was studied. RNFL thickness and optic disc topographic parameters were measured using Swept-Source OCT Triton (Topcon) and were compared between groups using a variance analysis. Correlation between the AL and the study variables was performed using a Pearson's correlation coefficient test.

Results: The RNFL thickness was lower in eyes with higher AL in the superior (r=-0.41; p<0.001), inferior (r=0.58; p<0.001) and nasal (r=-0.43; p<0.001) quadrants, in the mean value of the RNFL (r=-0.49; p<0.001), optic disc area (r=-0.40; p<0.001) and rim area (r=-0.25; p=0.01).

Conclusions: AL is negatively correlated with RNFL thickness and optic disc topographic parameters measured by Swept-Source OCT Triton (Topcon).