Superficial foveal avascular zone area changes before and after idiopathic epiretinal membrane surgery

Abstract

To investigate the foveal morphological changes and foveal avascular zone (FAZ) area before and after epiretinal membrane (ERM) surgery. Twenty-two eyes with treatment-naive ERM were included in this retrospective study. The central foveal thickness (CFT) and FAZ area were measured via swept-source optical coherence tomography (SS-OCT) and OCT angiography pre- and postoperatively. The unaffected fellow eyes were used as controls. The preoperative superficial FAZ area was significantly smaller in patients (0.08±0.04 mm²) than in controls (0.33±0.09 mm²; P<0.001). The postoperative superficial FAZ (0.12±0.06 mm²) area was significantly greater than the preoperative area (P<0.001). The preoperative superficial FAZ area was strongly negatively correlated with CFT (P<0.001, rho=-0.763). ERM induced significant foveal morphological changes and reduction of the superficial FAZ area. Foveal thickness was restored and FAZ area increased postoperatively. However, the process is rather slow and the recovery is incomplete.

Keywords: central foveal thickness; epiretinal membrane; foveal avascular zone; optical coherence tomography angiography.

Figure 1. OCTA images of a 55 years old female patient with unilateral ERM

The SCL of the affected eye before ERM surgery (A), and of the affected right eye at postoperative 5mo (B), and of the unaffected fellow eye (C). Longitudinal scans showed the corresponding segmentation layers (D-F). The superficial FAZ was shown within the green line. Preoperative OCTA image (G) showed the distortion of the superficial retinal vasculature, the reduction and deformation of the FAZ area (0.058 mm²). Postoperative OCTA image at 5mo (H) showed the increase in the superficial FAZ area (0.108 mm²) and partial normalization of the vascular structure. The OCTA image of the SCL in the unaffected fellow eye (I). Its FAZ area measured 0.455 mm².

Figure 2. The relationship between superficial FAZ area and CFT

The area of the preoperative superficial FAZ was strongly negatively correlated with the preoperative CFT (A; P<0.001, rho=-0.763). The areas of the FAZ in the postoperative (B) and control groups (C) were moderately negatively correlated with the respective CFTs (P=0.032, rho=-0.379 and P=0.007, rho=-0.555, respectively).