POLYPOIDAL CHOROIDAL NEOVASCULARIZATION VERSUS TYPE 1 CHOROIDAL NEOVASCULARIZATION IN AGE-RELATED MACULAR DEGENERATION: A Fractal Analysis Study

To compare quantitative optical coherence tomography angiography parameters between polypoidal choroidal neovascularizations (PCNVs) and Type 1 choroidal neovascularizations (CNVs) in patients with age-related macular degeneration. METHODS: PCNV and Type 1 CNV lesions were retrospectively recruited in a cohort of patients with age-related macular degeneration. All the patients underwent a comprehensive ophthalmic evaluation, including best-corrected visual acuity, fluorescein and indocyanine green angiography, structural optical coherence tomography (OCT), and optical coherence tomography angiography. Vascular perfusion density, fractal dimension, and lacunarity were computed by means of fractal analysis of neovascular en face optical coherence tomography angiography slabs. RESULTS: Sixty-eight eyes were included in the analysis. Of them, 35 of 68 eyes (51.5%) had PCNV and 33 of 68 (48.5%) had Type 1 CNV. Patients with PCNV were significantly younger (P = 0.0003) and had a higher best-corrected visual acuity (P < 0.0001). The mean vascular perfusion density was 0.83 ± 0.11% in PCNVs and 0.46 ± 0.10% in Type 1 CNVs (P < 0.0001). The mean fractal dimension was 1.44 ± 0.1 in PCNVs and 1.45 ± 0.09 in Type 1 CNVs (P = 0.86) while the mean lacunarity was 2.46 ± 1.03 in PCNVs and 1.86 ± 0.52 in Type 1 CNVs (P = 0.006). CONCLUSION: PCNVs resulted to be more heterogeneous and characterized by higher vascular perfusion density and lacunarity values than Type 1 CNVs. These interesting findings seem to support the idea that PCNVs and Type 1 CNVs are two separate clinical entities. However, future studies based on optical coherence tomography angiography fractal analysis, but also involving other relevant parameters such as demographics, presentation, morphology on multimodal imaging, and response to treatment, are necessary before drawing any definitive conclusions on whether PCNV is a specific clinical entity or a neovascular age-related macular degeneration variant.