Reduced vessel density in the superficial and deep plexuses in diabetic retinopathy is associated with structural changes in corresponding retinal layers.

Carlo Lavia,Ali Erginay,Aude Couturier,Alain Gaudric,Bénédicte Dupas,Ramin Tadayoni,Demetrios G Vavvas

doi:10.1371/journal.pone.0219164

Abstract

PurposeTo explore the relationships between vessel density (VD) in the retinal vascular plexuses with the thickness and structural changes of their corresponding retinal layers in patients with diabetic retinopathy (DR).MethodsRetrospective analysis of 17 eyes of 17 Type 1 diabetes (T1D) patients with severe non-proliferative or proliferative DR and no current or past macular edema. Seventeen age- and sex-matched healthy subjects were included as controls. Using optical coherence tomography (OCT) and OCT-angiography (OCTA), VD was measured in the superficial vascular plexus (SVP) and deep vascular complex (DVC) that includes the intermediate (ICP) and deep capillary plexuses (DCP), and compared to the retinal thickness (RT) of the inner (from the inner limiting membrane to the inner plexiform layer) and intermediate (inner nuclear and outer plexiform layer) retinal layers. The correlation between the inner and intermediate RT and the VD of the corresponding vascular networks (SVP and DVC, respectively) was assessed. All OCT and OCTA examinations were performed using the RTVue XR Avanti (Optovue, Fremont, CA).ResultsThe inner RT and VD in all plexuses were significantly reduced in T1D patients compared to healthy subjects. The capillary drop-out patterns were polygonal and well-defined in the SVP while the ICP and DCP showed a more diffuse capillary rarefaction and a VD that varied in the same proportion. The inner RT significantly correlated with VD in the SVP (r = 0.71 in healthy subjects and r = 0.62 in T1D patients, p <0.01). The intermediate RT did not significantly correlate with VD in the DVC.ConclusionsIn T1D subjects, OCTA allowed observing different capillary drop-out patterns in the SVP and in the ICP-DCP, with different structural changes in the corresponding retinal layers, suggesting that they should be considered as distinct anatomical and functional entities.

Highlights

Macular thickening was the first optical coherence tomography (OCT) parameter found to be correlated with visual acuity (VA) in the context of macular edema (ME) [1,2]
The inner retinal thickness (RT) and vessel density (VD) in all plexuses were significantly reduced in Type 1 diabetes (T1D) patients compared to healthy subjects
The capillary drop-out patterns were polygonal and well-defined in the superficial vascular plexus (SVP) while the intermediate capillary plexus (ICP) and deep capillary plexuses (DCP) showed a more diffuse capillary rarefaction and a VD that varied in the same proportion

Summary

Introduction

Macular thickening was the first optical coherence tomography (OCT) parameter found to be correlated with visual acuity (VA) in the context of macular edema (ME) [1,2]. On the other hand, an excessive thinning of the macula appears to be associated with a poorer VA [4,5]. With more detailed retinal structure analysis provided by spectral-domain OCT (SD-OCT), the concept of disorganization of retinal inner layers (“DRIL”) has emerged to characterize cases in which a retinal thinning is associated with the loss of recognizable boundaries between retinal cellular layers in the context of capillary non-perfusion, suggesting some degree of cellular loss [6,7].

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