Swept-source optical coherence tomography angiography metrics of retinal ischaemic perivascular lesions in patients being evaluated for carotid artery stenosis and controls

BACKGROUND/AIMS: Retinal microvascular ischaemia may produce localised middle retinal disruption with corresponding scotoma, a phenomenon termed paracentral acute middle maculopathy (PAMM). Small chronic middle retinal atrophic lesions termed retinal ischaemic perivascular lesions (RIPLs) appear qualitatively similar to PAMM lesions and have recently been hypothesised to result specifically from PAMM. However, no studies have quantitatively demonstrated an ischaemic origin of RIPLs. We quantitatively investigated the pathophysiology of RIPLs and their relationship with PAMM with swept-source optical coherence tomography angiography (SS-OCTA). METHODS: A total of 14 controls and 25 patients being evaluated for carotid artery stenosis (CAS) were enrolled. SS-OCTA imaging of each eye was taken. Projection-resolved en face 6 mm × 6 mm superficial capillary plexus (SCP) and deep capillary plexus (DCP) images were quantitatively analysed with two algorithms for changes in vessel linear density (VLD) and vessel tortuosity (VT) at RIPLs relative to both the immediately surrounding macula and the entire macula, as well as between eyes with RIPLs and eyes without RIPLs. RESULTS: All controls and 22 of 25 CAS patients were included in the analysis. RIPLs demonstrated a localised decrease in DCP VLD in CAS patients and controls. RIPLs tended to show a localised decrease in SCP VLD in CAS patients but a localised increase in controls. No changes in VT were found. Eyes with RIPLs had VLD and VT similar to their RIPL-free fellow eyes. CONCLUSION: RIPLs are associated with quantifiable local, but not global, ischaemia, supporting the idea of shared pathophysiology with classic PAMM lesions along a continuum of ischaemia severity.