Effect of refractive status on peripapillary retinal nerve fibre layer thickness: a study by RTVue spectral domain optical coherence tomography

Aim To evaluate the influence of axial length on retinal nerve fibre layer (RNFL) thickness in myopic, hyperopic and emmetropic eyes by spectral domain optical coherence tomography (OCT). Methods Subjects were divided into three groups: myopic (n=35), emmetropic (n=30) and hyperopic eyes (n=33). RNFL thickness was obtained from all octametric section parameters by RTVue OCT. Axial length and spherical equivalent values were determined for all patients. Results RNFL thickness values, except for lower and upper nasal sectors, were thinner in the myopic eyes than in the hyperopic eyes. Average RNFL thickness and the RNFL thicknesses of the superotemporal, superonasal, inferotemporal and lower temporal sectors were significantly different between the myopic and emmetropic eyes, and average RNFL thickness and the RNFL thicknesses of the upper temporal and inferonasal sectors were significantly different between the hyperopic and emmetropic eyes. The average peripapillary RNFL thickness had a negative correlation with axial length (r=-0.741, p<0.001). However, after correction of the magnification effect, the significant differences disappeared. Conclusions We have shown that axial length/refractive status affected the peripapillary RNFL thickness profile measured by RTVue OCT. To make a correct diagnosis for glaucoma, either the axial length-induced magnification effect should corrected by ophthalmologists or the RTVue OCT database should be improved by taking axial length into account.