The effect of myopia on retinal nerve fibre layer measurement: a comparative study of spectral-domain optical coherence tomography and scanning laser polarimetry.

Background/aim To evaluate the effect of myopia on retinal nerve fibre layer (RNFL) thickness measurement by using spectral domain optical coherence tomography (Cirrus HD OCT) and scanning laser polarimetry with enhanced corneal compensator (GDx ECC). Methods One hundred and forty-nine eyes of 149 myopic subjects were recruited and subdivided into three groups according to their refractive errors: high myopia group (spherical equivalent (SE)<=-6 D); moderate group (-3 D >= SE>-6 D); low group (-0.5 D >= SE>-3 D). RNFL thickness was measured by Cirrus High Definition (HD) OCT and GDx ECC. Associations between RNFL thickness and axial length/SE were evaluated by using Pearson correlation analysis. Results Average RNFL thickness measured with Cirrus OCT correlated significantly with axial length (r=-0.322, p<0.001) and SE (r=0.291, p<0.001). No significant correlation was detected between axial length (r=-0.068, p=0.407)/SE (r=0.109, p=0.187) and RNFL thickness measured with GDx ECC. Conclusion Average RNFL thickness measured with Cirrus HD OCT decreases as the degree of myopia increases while no such correlation was detected in GDx ECC. Histological studies are warranted to further our understanding of the relationship between RNFL thickness and myopia.