Multimodal evaluation of choroidal vascular alterations after panretinal photocoagulation in diabetic retinopathy

PURPOSE: To evaluate morphological and quantitative changes in the choroid after panretinal photocoagulation (PRP) for diabetic retinopathy using multimodal imaging and to identify factors associated with these changes. METHODS: This retrospective study included 48 eyes of 26 patients with severe non-proliferative or proliferative diabetic retinopathy. Ultra-widefield indocyanine green angiography (UWF-ICGA) and enhanced-depth imaging optical coherence tomography (EDI-OCT) were performed before and after PRP. Choroidal vessel density, fractal dimension (FD), and hyperpermeable area were quantified from fluorescein angiography-subtracted ICGA images using ImageJ and Fractalyse software. Choroidal vascularity index (CVI), subfoveal choroidal thickness (SFCT), and Haller's layer thickness were measured on EDI-OCT. CVI was calculated as the ratio of the luminal area to the total subfoveal choroidal area within a 1,500-µm region. Relationships among choroidal and retinal parameters were analyzed by multivariable regression. RESULTS: After PRP, the mean hyperpermeable area significantly decreased (8.78%→7.95%, p < 0.001), accompanied by reductions in choroidal vessel density (34.67%→33.34%, p < 0.001), FD (1.662→1.632, p = 0.003), SFCT (266.63→242.75 μm, p < 0.001), and CVI (64.34%→62.13%, p < 0.001). Haller's layer thickness was independently associated with the hyperpermeable area, while CVI correlated with central retinal thickness and Haller's layer thickness. CONCLUSION: PRP reduces choroidal vascular congestion and complexity, suggesting structural remodeling of the choroidal vasculature associated with reduced vascular permeability. Quantitative ICGA- and OCT-derived indices may serve as noninvasive biomarkers for evaluating choroidal remodeling and treatment response after PRP in diabetic retinopathy.