Quantitative evaluation of damage to retinal capillaries caused by half-dose and half-time photodynamic therapy with optical coherent tomographic angiography

•In order to minimize the side effects of the laser therapy as much as possible, we further studied the influence of PDT with different parameters on normal retinal capillaries, trying to find a parameter with good therapeutic effect and small side effects. In this work, we compared the full-dose PDT of halving the time and the half-dose PDT of whole time for the treatment of patients with CSC and the effect on the normal retinal capillaries. : To determine and compare retinal capillaries damage in patients with chronic central serous chorioretinopathy (CSC) after half-dose and half-time photodynamic therapy (PDT) based on optical coherence tomographic angiography (OCTA). : Thirty-three eyes of 33 patients and 32 eyes of 32 patients with active CSC were treated with half-dose PDT and half-time PDT respectively and followed up for 3 months. Fundus fluorescein angiography (FFA) and indocyanine green angiography (ICGA) were performed at baseline; best corrected visual acuity (BCVA) and OCTA were performed at baseline, 3-day, 7-day, 14-day, 1-month, and 3-month follow-up visits. : Twenty-eight patients in half-dose group and 27 patients in the half-time group finished the 3-month follow-up visits. BCVA was significantly improved at post-PDT 1 month and 3 months (both P < 0.05) and central macula thickness (CMT) was significantly decreased at all post-PDT time points (all P < 0.05) in both groups. 22 patients (78.57%) in the half-dose group and 21 patients (77.78%) in the half-time group had complete absorption of subretinal fluid (SRF) at post-PDT 3 months. There was no significant difference in the above-mentioned prognostic measurements between two groups. The mean vessel densities of superficial retina (VDSR) and inner retina (VDIR) layers were decreased at all post-PDT time points in both groups. However, the decrease of VDIR and VDSR at post-PDT 3 days and 3 months in the half-dose group was much severe than those in the half-time group (P < 0.05). : Both half-dose and half-time modifications of PDT were similarly effective in improving the BCVA and decreasing the SRF for chronic CSC. However, the retinal capillaries damage in the half-time group was less severe than that in the half-dose group, so the half-time modification may be a more appropriate parameter for patients with chronic CSC.