Abstract:  Objective To study longitudinal changes in retinal and choroidal capillary circulation in eyes treated with iodine 125 (¹²⁵I) plaque brachytherapy for uveal melanoma with OCT angiography (OCTA), and to explore changes in ocular blood flow before radiation retinopathy (RR). Design Prospective cohort study. Participants 30 patients diagnosed with choroidal melanoma from May 2017 to July 2018 and underwent 125I scleral radiotherapy. Methods Patients underwent OCTA examinations before 125I plaque brachytherapy, 1 day, 1 month, 3 months, 6 months and 12 months after the surgery. Retinal vascular density and choroidal capillary density were measured respectively and the correlation between visual acuity and OCTA parameters were analyzed. Main Outcome Measures Best corrected visual acuity(BCVA), retinal thickness, vacular density of the superficial and deep retinal in parafovea area, foveal avascular zone (FAZ) area, FD-300 area density, FD-300 length density and choroidal capillary vascular density. Results Before plaque brachytherapy, compared with the contralateral uninvolved eye, the choroidal melanoma eyes had thicker central macular thickness (P=0.004), lower parafoveal vascular density in superficial (P=0.05) and deep (P<0.001) retinal layer, smaller FAZ area (P=0.002), lower FD-300 area density (P<0.001), lower FD-300 length density (P=0.042), and lower choroidal capillary density (P=0.001). Patients were followed up for up to 12 months and found that FD-300 area density (P<0.001) and length density (P=0.007) gradually decreased. Although without statistically significant (all P>0.05), the superficial retinal vascular density gradually decreased with time, while the choroidal capillary vascular density increase at first and then decreased. Prior to scleral radiation application, the visual acuity of the affected eye was significantly correlated with the distance of the tumor from the optic disc (P=0.006) and macula (P=0.021). Multivariate linear regression analysis showed that 1 month after scleral radiation application, after adjusting the age and the distance of the tumor from the optic disc, the BCVA of the affected eye was significantly negatively correlated with central macular thickness. Conclusion Patients with choroidal melanoma had undergone changes in retinal and choroidal blood flow before receiving scleral radiotherapy, and the superficial retinal blood flow density gradually decreased as time passed after the plaque brachytherapy. It suggests that there may have been retinal vascular changes before the occurrence of radiation retinopathy. The retinal vascular changes existed before the occurrence of RR, which provides a new basis for the diagnosis and treatment timing of RR. (Ophthalmol CHN,  2021, 30: 102-107)

Key words: radiation retinopathy, optical coherence tomography angiography, choroidal melanoma