Effect of myopia and optic disc area on ganglion cell-inner plexiform layer and retinal nerve fiber layer thickness

Purpose: The aim of this work was to study the impact of myopia and different optic disc areas on ganglion cell-inner plexiform layer (GCIPL) and retinal nerve fiber layer (RNFL) thickness profiles in myopic patients by spectral-domain optical coherence tomography (SD-OCT). Methods: This was a cross-sectional study of 100 eyes of 50 myopic individuals. All patients underwent complete ophthalmic evaluation and SD-OCT examination. According to spherical equivalent (SE), patients were divided into M1, M2, and M3 (low, moderate, and high myopia group). According to optic disc area values, patients were divided into D1, D2 and D3 (small, medium and large disc groups). Average GCIPL and RNFL thickness recorded globally and separately for all quadrants and also according to 12 clock hours and analyzed with respect to different myopic groups, optic disc area groups, and axial length. Results: Quadrantic RNFL thickness profiles and their average RNFL thickness were significantly thinner in high myopic group compared to low myopic group, except for the temporal quadrant (P < 0.05). Average RNFL and RNFL thickness of all quadrants were significantly thicker in the large disc group than in the small disc group (P < 0.05). Average GCIPL and GCIPL thicknesses of all sectors were significantly thinner in high myopic group compared to low myopic group (P < 0.05). No significant correlation was observed between GCIPL and disc area changes. Average RNFL thickness correlated significantly with SE (3.667 μm/diopter), axial length (–5.3805 μm/mm) and optic disc area (9.4617 μm/mm2). Also, average GCIPL thickness correlated statistically significantly with SE (1.6807 μm/diopter) and axial length (–2.626 μm/mm). Conclusion: Myopia and axial length significantly reduce RNFL and GCIPL thickness profiles but the optic disc area significantly increases RNFL thickness, but not GCIPL thickness.