Purpose: Automated segmentation of retinal layers by spectral-domain optical coherence tomography (SD-OCT) is usually erroneous in the presence of retinal diseases. The purpose of this study is to report the changes in ganglion cell complex (GCC) comprising retina nerve fiber layer (RNFL), ganglion cell layer (GCL), and inner plexiform layer (IPL) in neovascular age-related macular degeneration (AMD) patients by manually correcting the automated segmentation errors.
Methods: Thirty eyes of 30 patients with new-onset choroidal neovascularization secondary to neovascular AMD and 30 eyes of 30 healthy subjects were included. The inner retinal thicknesses were measured using early treatment diabetic retinopathy circle in the central 1 mm (fovea) and surrounding 3 mm diameter (parafovea) after checking the accuracy of automated segmentation lines. Manual segmentation was done to ensure the accurate segmentation, when needed.
Results: Neovascular AMD patients had thicker mean RNFL, GCL, IPL, and GCC thicknesses within the fovea compared to healthy eyes (p = 0.04, p = 0.001, p = 0.032, and p = 0.005, respectively). In the parafoveal area, among the thickness-related measurements, the only significant difference was a thicker mean RNFL (p = 0.002).
Conclusion: Diffuse thickening of inner retinal layers in neovascular AMD may overestimate actual GCC thickness within fovea. This pseudo-increase in GCC thickness and inner retinal layers in general likely does not reflect more cells or tissue, but rather diffuse edema which leads to a falsely increased reading of layer thickness. Such false readings may also make the assessment of other conditions that lead to reduced inner retinal layer thickness such as glaucoma, optic nerve disease, or retinovascular occlusions more difficult.
Keywords: Choroidal neovascularization; GCC; Ganglion cell complex; Ganglion cell layer; Neovascular AMD; OCT; Segmentation.