The content of this research project is to identify the angiofibrotic switch, the transition from angiogenesis to fibrosis, in neovascular age-related macular degeneration (nAMD) longitudinally. Despite optimal treatment about 50% of eyes with nAMD develop fibrosis within 2 years, causing irreversible damage to the retina and functional loss. Objective measurement of fibrosis, however, is challenging, since clinical staging is subjective and current imaging modalities such as color fundus photography (CFP), fluorescein angiography (FA) and optical coherence tomography (OCT) often do not allow clear delineation. Novel imaging modalities such as polarization-sensitive OCT (PS-OCT), OCT angiography (OCTA) and adaptive-optics OCT (AO-OCT) offer identification of fibrous components and microvasculature of fibrotic lesions non-invasively with highest precision and shall thus be used in this study.

Hypotheses: The investigators hypothesize to detect and quantify subclinical (i.e. not detectable on dilated fundus examination) areas of fibrosis using PS-OCT and determine the rate and exact location within the neovascular lesion. Furthermore, the investigators expect neuroretinal and microvascular changes, which will be assessed by AO-OCT and OCTA.

Methods: Eighty eyes of 80 patients with chronic nAMD will be included and examined cross- sectionally to evaluate the accuracy of PS-OCT to detect and quantify fibrosis in comparison to gold standard imaging modalities. In addition, OCTA and AO-OCT will be performed to analyze the relationship between fibrous, neovascular and neuroretinal structures. Furthermore, forty eyes of 40 participants with treatment-naïve nAMD will be included and followed over 12 months with predefined follow-up intervals. Novel non-invasive imaging will be applied to objectively determine the exact time and extent of the angiofibrotic switch in nAMD during state-of-the- art therapy. This approach has not been done before and is clinically relevant for multiple reasons: Firstly, only little is known about the development of fibrosis in AMD during therapy. Secondly, the clinical diagnosis of subretinal fibrosis is subjective and does not allow reliable quantification. Thirdly, current gold standard imaging modalities (i.e. CFP and FA) for detection of fibrosis involve invasive and time-consuming procedures and do not allow three-dimensional analysis. Finally, our study may identify objective endpoints for future interventional trials.

Research questions/hypotheses: Age-related macular degeneration (AMD) is the main cause of legal blindness among elderly patients in industrialized countries. The main reason for severe and irreversible visual impairment among these patients is subretinal fibrosis (SF). Large-scale interventional trials (e.g. CATT) have shown that half of all eyes affected by choroidal neovascularization (CNV) develop clinically visible fibrotic scarring over two years despite optimal treatment, causing irreversible retinal damage and functional loss. Thus, prevention of fibrosis in AMD is currently the focus of researchers worldwide. Clearly defined end points for interventional trials, however, are lacking because detection and quantification of SF is challenging. Clinical staging of SF is subjective and current gold standard imaging modalities such as color fundus photography (CFP), fluorescein angiography (FA) and optical coherence tomography (OCT), even in concert, do not allow a distinct and early delineation of SF. Novel imaging modalities such as polarization-sensitive OCT (PS-OCT), OCT angiography (OCTA) and adaptive optics (AO)-OCT are promising means to objectively detect SF and provide detailed insights into the biology of the microvascular and neurosensory compartments. Our group recently demonstrated that PS-OCT offers automated identification and quantification of SF in AMD based on tissue-specific contrast. Aim of the proposed research project is to detect and characterize the angiofibrotic switch, i.e. the transition from active and reversible neovascularization to irreversible fibrosis, in neovascular AMD under anti-VEGF treatment. We hypothesize to detect the initiating events of fibrotic conversion including even subclinical stages of fibrosis by non-invasive PS-OCT and identify the association with fibrovascular and retinal changes by OCTA and AO-OCT, respectively.

Scientific/scholarly innovation/originality of the project: The combination of PS-OCT, OCTA and AO-OCTA to non-invasively detect pathognomonic features of fibrovascular conversion is a novel and unprecedented approach towards objective visualization and quantification of disease pathomechanisms. Outcomes of this study may provide clearly defined morphological endpoints for future interventional trials.

Methods: Eighty eyes of 80 patients with chronic nAMD will be included and examined cross-sectionally to evaluate the accuracy of PS-OCT to detect and quantify fibrosis in comparison to gold standard imaging. In addition, OCTA and AO-OCT will be performed to analyze the relationship between fibrous, vascular and retinal structures. Furthermore, forty eyes of 40 participants with treatment-naïve nAMD will be included in a prospective study and followed for one year under treatment. PS-OCT, AO-OCT and OCTA imaging will be performed according to a standardized protocol at predefined visits. Gold standard imaging will be performed for validation.

Inclusion Criteria:

• Chronic neovascular AMD with anti-VEGF treatment of a minimum duration of 12 months (cohort 1)
• Treatment-naïve active neovascular AMD (cohort 2)
• 50 years of age or older
• Visual acuity 20/25-20/320
• At least one druse (>63μm) in either eye or late AMD in the fellow eye
• Fibrosis <50% of total lesion area at baseline (cohort 2)

Exclusion Criteria:

• Previous treatment for CNV in the study eye (cohort 2)
• Presence of other progressive retinal disease likely to affect visual acuity
• Contraindications for treatment with anti-VEGF
• Pregnancy
• Dyslexia

There will be two study cohorts in this trial:

1. 80 participants with neovascular AMD and a minimum history of 12 months of anti- VEGF therapy will be included in cohort 1 and examined only once (1 study visit).
2. 40 participants with treatment-naive neovascular AMD receiving standardized anti- VEGF therapy will be included in cohort 2 and followed for 12 months (6 study visits).