The RTVue XR Avanti Spectral-Domain OCT system (Optovue, Inc.) with radial line scan was used to image the macular retina. All measurements were performed by a single, well-trained examiner. A radial scanning mode with 18 lines was applied to generate the 3D thickness maps (
Fig. 2A). After SD-OCT image acquisition, data derived from the images were processed automatically by using a custom software to segment the eight intraretinal layers (
Fig. 2C) as already described in our previously published articles.
21,22 Manual inspection and a few corrections were still required, especially in low-quality images. In the current study, the retina was divided into retinal nerve fiber layer (RNFL), ganglion cell layer and inner plexiform layer (GCIP), inner nuclear layer (INL), outer plexiform layer (OPL), Henle fiber layer and outer nuclear layer (HFL+ONL), myoid and ellipsoid zone (MEZ), outer segment of the photoreceptor cell (OS), and interdigitation zone and retinal pigment epithelium (IZ+RPE). For each eye included in this study, a 3D thickness map of the intraretinal layers in each eye was generated based on the segmented layers. For analysis, the macular thickness map was divided into nine sectors and was displayed in three concentric circles, including a central circular subfield (1-mm diameter), an internal ring (0.5–1.5 mm from the fovea), and an external ring (1.5–3.0 mm from the fovea) (
Fig. 2B). The three concentric areas were then divided into nine sectors, including the central (C) and S, I, T, and N regions of the internal ring (SI, II, TI, and NI, respectively) and the S, I, T, and N regions of the external ring (SE, IE, TE, and NE, respectively). The mean thickness for the total retinal in each sector was calculated.