Influence of Axial Length on Peripapillary Retinal Nerve Fiber Layer Thickness in Children: A Study by RTVue Spectral-Domain Optical Coherence Tomography

Purpose: To evaluate the influence of axial length on peripapillary retinal nerve fiber layer (RNFL) thickness in myopic, hyperopic and emmetropic children eyes by RTVue optical coherence tomography (OCT). Methods: One hundred twenty eyes of 120 children including 40 myopic, 40 emmetropic and 40 hyperopic eyes were enrolled in the study. Peripapillary RNFL thickness measurements were performed using spectral-domain RTVue OCT (Optovue, Fremont, CA). RNFL thickness parameters were obtained from all octametric sections: upper temporal (TU), superotemporal (ST), superonasal (SN), upper nasal (NU), lower nasal (NL), inferonasal (IN), inferotemporal (IT) and lower temporal (TL). Spherical equivalent refractive error was determined via cycloplegic auto-refraction (Topcon, Tokyo, Japan). The axial length was measured using IOLMaster (Carl Zeiss MEDITEC). Littmann formula was used for correction of axial length-related ocular magnification effect. Results: Peripapillary RNFL thicknesses were significantly different among the three groups in all sectors except for NU and IT sectors. RNFL thicknesses in all sectors except for TU and TL sectors had significant negative correlations with axial length. However, these differences (excluding TU and TL sectors) and correlations disappeared after correction of magnification effect. Conclusion: In conclusion, axial length influences peripapillary RNFL thickness as measured by RTVue OCT. However, this appears to be due to the ocular magnification effects associated with axial length and can be corrected for with the application of the Littman formula.