ObjectiveTo observe and analyze the subfoveal choroidal thickness (SFCT), large choroidal vessel layer thickness (LCVT), and their early changes, and to evaluate their prognostic value for treatment outcomes in eyes with polypoidal choroidal vasculopathy (PCV) receiving anti-vascular endothelial growth factor (VEGF) therapy. MethodsA retrospective clinical study. A total of 120 patients (120 eyes) with unilateral PCV diagnosed and confirmed at Tangshan Eye Hospital from January 2020 to August 2024 were included. All affected eyes received intravitreal anti-VEGF injections. SFCT and LCVT were measured using swept-source optical coherence tomography (SS-OCT) before treatment and at 1, 3, 6, and 12 months after treatment. Based on the 12-month follow-up outcomes, the eyes were divided into a good prognosis group (69 eyes) and a poor prognosis group (51 eyes). Subretinal fluid (SRF) absorption was assessed by SS-OCT at 1 month after the first treatment (early stage). Repeated measures ANOVA was used to compare the dynamic changes of SFCT and LCVT between the two groups. Binary logistic regression, joint modeling, receiver operating characteristic (ROC) curves, decision curve analysis (DCA), and mediation analysis were used to evaluate the predictive value of SFCT and LCVT for prognosis. ResultsCompared with the good prognosis group, the poor prognosis group had significantly greater disease duration, best-corrected visual acuity, branching vascular network area, maximum linear lesion distance, proportion of choroidal vascular hyperpermeability, pigment epithelial detachment height, and pre-treatment SFCT and LCVT (P＜0.05). The good prognosis group had significantly lower SRF height (SRFH) before treatment and at 1 month after treatment, and a greater reduction in SRFH (ΔSRFH) within the first month, compared with the poor prognosis group (P＜0.05). At 1 month after treatment, complete SRF absorption was observed in 65 eyes (94.20%, 65/69) in the good prognosis group and 32 eyes (62.75%, 32/51) in the poor prognosis group; the complete SRF absorption rate was significantly higher in the good prognosis group (χ2=18.731, P＜0.001). Repeated measures ANOVA showed that SFCT and LCVT significantly decreased after treatment at different time points in both groups (P＜0.05); at each post-treatment time point, SFCT and LCVT were significantly higher in the poor prognosis group than in the good prognosis group (P＜0.05). Cohen's d effect size analysis showed that the intergroup difference in LCVT was greater than that in SFCT. ROC curve analysis showed that pre-treatment SFCT and LCVT effectively predicted early complete SRF absorption, and LCVT had significantly better diagnostic performance than SFCT [area under the ROC curve (AUC)=0.82, 0.76; P=0.025]. Joint modeling analysis showed that longitudinal changes in SFCT and LCVT were significantly associated with the risk of poor prognosis (P＜0.01); for every 50 μm increase in LCVT and SFCT, the relative risk of poor prognosis was 1.615 and 1.512, respectively. The Akaike information criterion value of the LCVT joint model (3 719.42) was lower than that of the SFCT model (3 852.67). At 1 month after treatment, ΔLCVT and ΔSFCT were both significant predictors of poor prognosis; in all adjusted models, the odds ratio of ΔLCVT was lower than that of ΔSFCT, indicating better predictive value. ROC curve analysis showed that both ΔSFCT and ΔLCVT had significant predictive value for poor prognosis, and ΔLCVT had significantly better predictive performance than ΔSFCT (AUC=0.81, 0.74). DCA showed that both ΔSFCT and ΔLCVT provided clinical net benefit, with ΔLCVT showing higher benefit. Mediation analysis showed that ΔLCVT and ΔSFCT partially improved prognosis by promoting early SRF absorption, with the indirect effect of ΔLCVT (39.35%) being higher than that of ΔSFCT (32.70%). ConclusionsBoth SFCT and LCVT can serve as predictors of prognosis in PCV eyes treated with anti-VEGF therapy. After controlling for the effect of SFCT, LCVT maintains independent predictive value, and its predictive efficacy is superior to that of SFCT.