Analysis of the inner and outer retinal layer thicknesses of patients with keratoconus

Clinical relevance The thickness of macular layers in healthy individuals and patients with keratoconus can be evaluated using segmentation analysis to identify potential relationships with clinical stages and to determine whether a more comprehensive approach to visual prognosis is needed.Background The aim of this study was to compare the retinal layer thicknesses of patients diagnosed with keratoconus with those of healthy controls.Methods This prospective study examined the right eyes of 75 patients with early, moderate and advanced keratoconus and those of 50 healthy individuals as controls. Patients with systemic diseases or additional ocular conditions were excluded. Keratoconus staging was performed according to the Belin ABCD system using Pentacam data. The central macular thickness and the thicknesses of both the inner retinal layers – retinal nerve fibre layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL) and inner nuclear layer (INL) – and outer retinal layers – outer nuclear layer (ONL), outer plexiform layer (OPL) and retinal pigment epithelium (RPE) – of all the subjects were assessed using spectral-domain optical coherence tomography segmentation analysis.Results The mean ages, gender distributions and axial lengths of the patients with keratoconus and those of the healthy controls were not significantly different (p = 0.560, p = 0.661, p = 0.117, respectively In the moderate and advanced stage groups, the mean thickness of the RNFL, GCL, IPL, and INL was statistically significantly higher compared to the mild stage and control groups (p = 0.041, p = 0.038, p = 0.032, and p = 0.029, respectively). Statistically significant thinning was detected in the ONL at the advanced stage (p = 0.001), with no statistically significant differences in the other outer layers.Conclusion The thicknesses of the retinal layers of keratoconus patients differ from those of healthy controls. Thickening of the inner retinal layers and thinning of the outer nuclear layer can be observed in advanced keratoconus. Long-term, multicentre observational studies are needed to clarify and explain the changes in the retinal layers of these patients.