Background/aims To identify characteristic retinal pigment epithelium (RPE) changes in fellow eyes of patients with neovascular age-related macular degeneration (nAMD) using polarisation-sensitive optical coherence tomography (PS-OCT).

Methods Thirty-one fellow eyes of 31 patients with unilateral nAMD were evaluated in this cohort study of a prospective interventional trial. PS-OCT as well as conventional imaging including spectral-domain (SD)-OCT and fluorescein angiography (FA) were performed using a standardised protocol. Monitoring visits were performed continuously at 1-month intervals. Morphological RPE features associated with the development of choroidal neovascularisation (CNV) were systematically analysed.

Results Mean follow-up was 29 months (±17, SD). Thirteen (42%) of 31 eyes developed de novo CNV: 9 eyes type I CNV, 2 eyes type II CNV, 2 eyes a retinal angiomatous proliferation lesion. RPE thickening and reticular pseudodrusen (RPD) were observed significantly more often in eyes that developed CNV than in eyes without CNV development (p<0.01). Monthly increase in drusen volume was higher in the CNV group with a median increase of +2.2% in area and +2.9% in volume compared with +0.8% and +0.6% in the non-progressing group. RPE migration within the neurosensory retina and at the level of the RPE resulting in RPE thickening was seen topographically and chronologically associated with CNV development.

Conclusions Conversion to CNV is associated with RPE-related changes such as RPE migration, RPE thickening, drusen volume or the presence of RPD. Early detection of these features may allow more efficient screening in risk eyes and timely vision-preserving treatment in eyes developing neovascular disease.