## 4 Discussion  
Previous studies also compared combination therapy of PDT with IVA or IVR for treating PCV. [PERSON] et al. and [PERSON] et al. reported no significant differences in changes in BCVA or CRT between the two groups 12 months after treatment [20; 21], which were similar to our results at the 12-month follow-up. However, [PERSON] et al. demonstrated significantly better BCVA in the IVA/PDT group at 18 and 24 months [22]. In our study, the BCVA improvement was significant in the IVA/PDT group, but not significant in the IVR/PDT group at the 18-month and 24-month follow-ups compared to baseline. However, there was no significant difference in the change of BCVA between the two groups. As for the change of CRT, previous studies reported significant reduction of CRT and subfoveal choroidal thickness in either the IVA/PDT group or the IVR/PDT group during a one-year follow-up period [20; 21]. Additionally, [PERSON] et al. demonstrated the change in subfoveal choroidal thickness was significantly larger in the IVA/PDT group than that in the IVR/PDT group [21]. In our study, the CRT reduction was not significant in the IVR/PDT group at the 18-month follow-up when compared to baseline. There was a significant difference in the dry macula rate at 18 months between the two groups, and the result was consistent with poor BCVA and CRT in the IVR/PDT group at the 18-month period. At the 24-month follow-up, the CRT reduced and the dry macula rate was achieved in 92.0% of patients in the IVR/PDT group, but the BCVA did not improve. This implies that, after retreatment for the recurrent disease, choriorental atrophy might develop, and the visual outcome was not as favorable as the anatomical outcome. As for the rate of complete polyp regression, [PERSON] et al. reported 76.9% in the IVA/PDT group and 78.2% in the IVR/PDT group at 12 months after treatment, without a significant difference between the two groups (\(p=0.57\)). Other studies reported 70.0% to 87.5% of the 3-month period for the complete polyp regression rate in patients receiving IVA/PDT [17; 18], and 77.8% of the 6-month period for the complete polyp regression rate in patients receiving IVR/PDT. In our study, the 3-month polyp regression rate in both groups was inferior to that of previous studies (53.3% in the IVA/PDT group and 52.0% in the IVR/PDT group). In this present study, there was significantly less retreatment, additional IVI monotherapy, and additional combination therapy in the IVA/PDT group than those in the IVR/PDT group. [PERSON] et al. also reported less additional combination therapy in the IVA/PDT group than that in the IVR/PDT group but without a statistically significant difference (\(p=0.08\)) [20]. [PERSON] et al. reported no differences in the retreatment rate, additional PDT, or IVI number between the two groups [22]. We demonstrated that younger patients and patients with better baseline BCVA had better visual outcome. [PERSON] et al. reported better visual outcome was correlated with better initial BCVA, a smaller greatest linear dimension, and greater subfoveal choroidal thickness [20]. [PERSON] et al. reported better final BCVA was associated with the female sex, better initial BCVA, IVA/PDT treatment, and a smaller greatest linear dimension [22]. This is the first study of comparison of the two-year outcome of combination therapy of PDT with IVA or IVR for PCV, which only enrolled participants in Taiwan. However, there were some limitations of the study. First, this study was retrospective and we could not control for certain confounding factors, including patients' physical condition and lifestyle. Second, our case number was relatively small. Third, there was a significant difference of gender between the two groups in our study, and this may be attributed to the small sample size. Finally, only patients with persistent or recurrent disease received repeated ICGA examination during 6 months to 24 months, so we could not obtain the data of a complete polyp regression rate through the whole period of the study.