OCT Biomarkers in Neovascular Age-Related Macular Degeneration: A Narrative Review

Abstract

Age-related macular degeneration (AMD) is the leading cause of legal blindness in elderly people. Neovascular AMD (nAMD) is responsible for the majority of cases of severe visual loss in eyes with AMD. Optical coherence tomography (OCT) is the most widely used technology for the diagnosis and follow-up of nAMD patients, which is widely used to study and guide the clinical approach, as well as to predict and evaluate treatment response. The aim of this review is to describe and analyze various structural OCT-based biomarkers, which have practical value during both initial assessment and treatment follow-up of nAMD patients. While central retinal thickness has been the most common and one of the first OCT identified biomarkers, today, other qualitative and quantitative biomarkers provide novel insight into disease activity and offer superior prognostic value and better guidance for tailored therapeutic management. The key importance of retinal fluid compartmentalization (intraretinal fluid, subretinal fluid, and subretinal pigment epithelium (RPE) fluid) will be discussed firstly. In the second part, the structural alterations of different retinal layers in various stages of the disease (photoreceptors layer integrity, hyperreflective dots, outer retinal tubulations, subretinal hyperreflective material, and retinal pigment epithelial tears) will be analyzed in detail. The last part of the review will focus on how alterations of the vitreoretinal interface (vitreomacular adhesion and traction) and of the choroid (sub-RPE hyperreflective columns, prechoroidal clefts, choroidal caverns, choroidal thickness and choroidal volume, and choroidal vascular index) interact with nAMD progression. OCT technology is evolving very quickly, and new retinal biomarkers are continuously described. This up-to-date review article provides a comprehensive description on how structural OCT-based biomarkers provide a valuable tool to monitor the progression of the disease and the treatment response in nAMD patients. Thus, in this perspective, clinicians will be able to allocate hospital resources in the best possible way and tailor treatment to the individual patient's needs.

Figure 1

Fluid distribution in neovascular AMD.

Figure 2

Structural OCT biomarkers: photoreceptors layer degeneration (white arrow).

Figure 3

Structural OCT biomarkers: hyperreflective dots (HRD; white arrows) and RPE detachment (black arrow).

Figure 4

Structural OCT biomarkers: outer retinal tubulations (black arrows).

Figure 5

Structural OCT biomarkers: subretinal hyperreflective material (SRHM; white arrow) and pigment epithelium detachment (white stars).

Figure 6

Structural OCT biomarkers: RPE tear (white bracket) and RPE layer retraction (white arrow).

Figure 7

Structural OCT biomarker: (a) vitreomacular adhesion (VMA, white arrows). The posterior hyaloid is partially detached, with a continuous adhesion on the foveal surface; (b) vitreomacular traction. The posterior hyaloid is fully detached but a foveal adhesion is present on the fovea with an evident traction.

Figure 8

Structural biomarker: prechoroidal clefts (white arrow).

Figure 9

Structural biomarker: choroidal caverns (white arrow).

Figure 10

Structural biomarker: manual caliper to measure choroidal thickness (CT).