The superficial capillary plexus perivascular gliosis occurring in retinitis pigmentosa revealed by multimodal retinal imaging

Purpose: In this study, our goal was to deepen the understanding of the clinical significance and underlying pathogenic mechanisms of the hyperreflective ganglion cell layer (HGB) observed in optical coherence tomography (OCT) scans of patients with retinitis pigmentosa (RP). Methods: The study was designed as observational, cross-sectional. RP patients with and without HGB were recruited and underwent complete multimodal retinal imaging assessment, including OCT, OCT angiography (OCTA) and Dense Automatic-RealTime (DART) OCTA. Morphological outcome measures included OCTA vessel density (VD), foveal avascular zone area and ellipsoid zone (EZ) width. Functional outcome measures were LogMAR best-corrected visual acuity (BCVA) and retinal sensitivity. Results: Twenty eyes with HGB (20 RP patients) and 20 eyes without HGB (20 RP patients) were included. A reference control group was included as well. RP eyes with HGB were characterized by significantly worse LogMAR BCVA and retinal sensitivity, compared with RP eyes without HGB. Moreover, HGB subgroup showed significantly worse VD values of intraretinal capillary networks. The main superficial capillary plexus (SCP) VD reduction was detected in the extrafoveal region. DART OCTA allowed to support the SCP perivascular gliosis pathogenic origin of HGB. DART OCTA was able to detect (I) SCP perivascular hyperreflectivity; (II) SCP perfusion signal reduction and (III) peripheral SCP capillaries closure. Conclusions: The presence of HGB is identified as an adverse finding in a subset of eyes affected by RP. HGB correlates with markedly deteriorated retinal morphology and function. The possible pathogenic mechanism underlying HGB manifestation is the perivascular gliosis of the SCP.