Subtle outer retinal and choroidal alterations in patients at high risk of progression to AMD

Abstract 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 of unilateral neovascular AMD (nAMD) were enrolled, twenty-two of the healthy contralateral eyes were considered at high risk of progression to AMD (Group1), the other twenty-five eyes were of dry AMD (Group2). Fifty healthy subjects (50 eyes) were enrolled as control. Swept-source optical coherence tomography equipped with angiovue was used to obtain three-dimensional retinal thickness maps, microvascular images of the superficial and deep retinal capillary plexuses (SCP and DCP) around the macula and choroid vessel index (CVI). Quantitative analyze was automatically calculated by inbuilt algorithm in the SS-OCT. RESULTS Compared to the controls, the densities of the SCP and DCP tend to decrease in Group2 without significance in all regions (P > 0.05). However, the CVI of patients in S and T regions was significantly decrease compared to the controls (P < 0.05). The outer retinal thickness of the Group1 trend to be increased without significance compared to the controls, while the Group2 in the C, S and T regions were significantly decreased compared to the controls and Group1. Meanwhile, compared to the controls, the thickness of total retina and choroid of the Group2 were significantly decreased (P < 0.05). The outer retinal thickness was significantly correlated to choroidal thickness in AMD patients. CONCLUSION Significantly thinning of outer retina and choroid were observed in patients with dry AMD. For eyes at high risk of progression to AMD, the outer retinal thickness trend to be increased while the choroidal thickness and CVI trend to be decreased. SS-OCT might be useful in evaluating the microstructural and blood supply disorders of the outer retinal layers in healthy eyes of unilateral nAMD patients, which might be a quantitative approach to identify the earliest progression of AMD.