Correlation analysis between foveal avascular zone and near peripheral retinal hypoperfusion in multiple sclerosis: a wide field optical coherence tomography angiography study

Abstract

The identification of non-invasive biomarkers to investigate and monitor retinal structural and vascular changes in multiple sclerosis (MS) represents an interesting source of debate. Until now optical coherence tomography angiography (OCTA) evaluated the foveal avascular zone (FAZ) and areas of retinal non-perfusion only in the macular region in MS patients. It could be interesting to identify possible biomarkers, useful in assessing the ischemic areas also in the near peripheral retina, since FAZ enlargement and the areas of peripheral retinal non-perfusions share common pathogenic processes. In this cross-sectional study, we investigated the correlation between the FAZ area and retinal vessel density (VD) in the near peripheral retina by new wide-field optical coherence tomography angiography (OCTA) in patients affected by relapsing-remitting multiple sclerosis (RR-MS). Moreover, we compared the FAZ area and the VD of superficial and deep capillary plexuses in the fovea region and in the near peripheral retina (6.4 × 6.4 mm) between RR-MS patients and healthy controls by means of a Solix full-range OCTA. Last, we also detected the changes in structural OCT parameters (ganglion cell complex and retinal nerve fiber layer). Thirty-three eyes of 33 RR-MS patients and 35 eyes of 35 healthy controls were enrolled. RR-MS patients showed a lower VD in the superficial capillary plexus and a significant increase in the FAZ area compared with controls. The deep capillary plexus revealed a reduced VD although not statistically significant in patients with respect to controls. In the patients' group, the FAZ area showed significantly negative correlations with VD of superficial capillary plexuses in the foveal and whole region, while the FAZ area did not negatively correlate with the VD of the deep capillary plexus. The significant correlations among OCTA parameters could demonstrate the FAZ area as a possible biomarker for assessing the perfusion status in the near peripheral retina, useful in RR-MS management. These findings could confirm the role of vascular dysfunction in the pathogenetic mechanisms of MS.

Keywords: FAZ; RRMS; multiple sclerosis; solix OCT; vessel density; widefield OCTA.

Figure 1

First row shows optical coherence tomography angiography (OCTA) images from a healthy subject's right eye (male, 30 years): normal superficial and deep capillary plexuses in terms of retinal vasculature texture (A,D) and in vessel density (B,E). The OCT B-scan (C,F) shows normal retinal profile, thickness. The foveal avascular zone (FAZ) shows a normal size of the area (G). Structural OCT reveals normal thicknesses of retinal nerve fiber layer (RNFL) (H) and ganglion cell complex (GCC) (I). The second row shows a patient's right eye (female, 31 years) affected by relapsing-remitting multiple sclerosis. OCTA images show in superficial capillary plexus a rarefaction in vascular texture (A1) and in vessel density (B1). The deep capillary plexus reveals focal rarefactions in terms of retinal vasculature texture (D1) and in vessel density (E1). The OCT B-scan (C1, F1) shows a normal retinal profile and thickness. The foveal avascular zone (FAZ) shows an evident enlargement of the area (G1). Structural OCT reveals several zones of reduced thicknesses of RNFL and GCC respect to healthy subject (H1, I1).