Imaging characterization of the fellow eye in patients with unilateral polypoidal choroidal vasculopathy.

Introduction: New insights on polypoidal choroidal vasculopathy (PCV) have shed light regarding its pathophysiology and associations. However, PCV characterization is still incomplete in Caucasians, which is due to presumed lower prevalence in this population. Features typically associated with AMD such as drusen, retinal pigmentary changes or atrophy are seen in PCV, as precursors and in the fellow eye. Pachychoroid spectrum, predisposing to PCV, also presents with chronic changes in the retinal pigment epithelium (RPE), such as drusen-like deposits (DLD), and in the choroid. The purpose of this study is to perform a multimodal imaging characterization of unaffected fellow eyes in a sample of Caucasian patients with unilateral PCV.

Methods: Multicenter retrospective cohort study with a sample of 55 unaffected fellow eyes from patients diagnosed with unilateral PCV confirmed by indocyanine green angiography. The sample was characterized in the baseline by color fundus photography, spectral domain optical coherence tomography (SD-OCT), fluorescein angiography and indocyanine green angiography. Morphological characteristics of both the retina and the choroid were evaluated. The SD-OCT of the last follow-up visit was also evaluated in order to exclude evolution to PCV or choroidal neovascularization. All images captured underwent evaluation by two independent graders. Informed consent was obtained from all participants.

Results: Fifty-five patients (median age, 74 ± 15 years) were included. After 15.5 ± 6.4 months of follow-up, only one developed disease (1.9%). Soft and/or hard drusen were present in 60% and pachydrusen in 23.6%. Pachychoroid signs were present in 47.2%, the double-layer sign in 36.4%, disruption of the RPE changes in 16.4% and RPE atrophy in 10.9%. ICGA revealed choroidal vascular dilation in 63.6% and punctiform hyperfluorescence in 52.7%. Branching vascular networks were identified in only 1.9% of cases.

Conclusion: The identification of pachychoroid signs in the OCT and ICGA were present in over half of the cases and the presence of the double-layer sign in more than a third provide crucial insights for enhanced characterization of this pathology and deeper understanding of its pathogenesis. These findings contribute significantly to the current knowledge, offering valuable markers to discern various phases of the pathology's progression.