Subtle outer retinal and choroidal alterations in patients at high risk of progression to age-related macular degeneration

Aim To explore the changes in the microstructure and blood supply of the outer retina in eyes at high risk of progression to age-related macular degeneration (AMD). Methods Forty-seven patients with unilateral neovascular AMD (nAMD) were enrolled. Twenty-two of the contralateral eyes were considered at high risk of progression to nAMD (Group 1), while the remaining 25 eyes had dry AMD (Group 2) Fifty healthy subjects (50 eyes) were enrolled as control. Swept-source optical coherence tomography (SS-OCT) equipped with angiovue (OCTA) was used to obtain three-dimensional retinal thickness maps and microvascular images of the superficial and deep retinal capillary plexuses (SCP and DCP) around the macula and choroid vessel index (CVI). Quantitative analysis was automatically calculated by an inbuilt algorithm in the SS-OCTA (VG200; SVision Imaging, Ltd., Luoyang, China). One-way analysis of variance (ANOVA) was used to compare the differences among the groups, and post hoc procedures were used to compare differences between the two groups. Associations between OCTA-derived parameters and retinal/choroidal thickness were evaluated using Pearson correlation coefficients. Results Compared to the controls, the densities of the SCP and DCP were significantly decreased in Group 2 in some regions ( p < 0.05). However, the CVI of patients in superior (S) and temporal (T) regions was significantly decreased compared to the controls ( P : 0.009, 0.020). The outer retinal thickness of Group 2 in the central (C), S, and temporal (T) regions were significantly decreased compared to the controls and Group 1 ( P : 0.004–0.048). Meanwhile, compared to the controls, the thickness of total retina and choroid of Group 2 were significantly decreased in most regions ( P : 0.001–0.034). The outer retinal thickness was significantly correlated to choroidal thickness in AMD patients ( r = 0.346, p = 0.034). Conclusion Significant thinning of outer retina and choroid were observed in patients with dry AMD. In eyes at high risk of progression to AMD, choroidal thickness and CVI tend to be decreased. SS-OCTA might be useful in evaluating microstructural and blood supply disorders of the outer retinal layers in healthy eyes of unilateral nAMD patients, which might be helpful to identify the earliest progression of AMD.