Choroidal Modifications Preceding the Onset of Macular Neovascularization in Age-Related Macular Degeneration

Introduction Macular neovascularization (MNV) is a common complication of age-related macular degeneration (AMD). Although several biomarkers may help to estimate the risk of MNV onset, neovascular complication is difficult to predict. Previous studies showed that the quantitative assessment of choroidal and choriocapillaris changes is useful for the assessment of atrophy expansion. On the other hand, scant data are available regarding the role of this kind of assessment in the setting of MNV. The aim of the study is to analyze choroidal and choriocapillaris changes occurring before the onset of MNV in patients affected by AMD using quantitative optical coherence tomography (OCT) and OCT angiography (OCTA). Methods The study was designed as a retrospective case series. Patients affected by AMD, categorized in eyes complicated by MNV and eyes not developing MNV, were retrospectively analyzed for 1 year of follow-up. Choroidal thickness (CT), Sattler layer thickness (SLT) and Haller layer thickness (HLT) were measured on OCT scans. Vessel density (VD) and choriocapillaris (CC) porosity were quantified on OCTA reconstructions. The main outcome measure was the relationship between choroidal and CC parameters, and MNV onset. Results We included 50 eyes of 50 AMD patients (28 male; mean age 74 +/- 5 years). Over the 1-year follow-up, 15/50 eyes developed MNV (9 type 1; 3 type 2; 3 mixed type 1-2). Mean best-corrected visual acuity (BCVA) was 0.15 +/- 0.15 logMAR at baseline, remaining stable in eyes not developing MNV (0.15 +/- 0.12 logMAR; p > 0.05), and worsening to 0.38 +/- 0.20 logMAR in eyes developing MNV (p < 0.01). VD values were similar between eyes developing MNV and eyes not complicated by MNV at baseline, with significant worsening detected only in MNV eyes. CC porosity was significantly higher in MNV eyes already before the onset of MNV. Furthermore, SLT was significantly lower in eyes developing MNV. The onset of MNV was preceded by a significant increase in intraretinal hyperreflective foci, whereas choroidal hyperreflective foci showed no evident changes. Conclusions The degeneration of CC and the SLT thinning represent early an biomarker of MNV onset in AMD.