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

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.

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.

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.

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.