Long-term Microvascular,Neural And Choroidal Changes After Panretinal Photocoagulation In Diabetic Retinopathy

Purpose:To evaluate the long-term retinal microvascular,neural,and choroidal changes in patients with severe non-proliferative diabetic retinopathy(NPDR)and proliferative diabetic retinopathy(PDR)following panretinal photocoagulation(PRP)using multimodal imaging technology.Methods:Our study included forty-five eyes with treatment-naive severe NPDR and PDR from 28 patients with type 2 diabetes including 14 severe NPDR patients(23 eyes),14 PDR patients(22 eyes),14 males(23eyes),14 females(23eyes),mean age(57.46±8.67)years old.All participants received the first PRP session after the baseline evaluation.And PRP was performed in three or four sessions with an interval of one week between sessions.The optical coherence tomography angiography(OCTA)and optical coherence tomography(OCT)examination was performed before PRP(baseline)and at 1 months,3 months,6 months,and 12 months after PRP.The optical coherence tomography angiography(OCTA)images were processed to qualitatively observe the macular arch,retinal non-perfusion area and retinal neovascularization,and quantify macular vessel density(VD),retinal thickness,foveal avascular zone(FAZ),peripapillary VD,retinal nerve fiber layer(RNFL)thickness and ganglion cell complex(GCC)thickness.Subfoveal choroidal thickness(SFCT)was measured using optical coherence tomography with enhanced depth-imaging technique(OCT-EDI).Neovascularization of the disc(NVD)and neovascularization elsewhere(NVE)were qualitatively observed by the leakage of fluorescein from areas of NV in fundus fluorescein angiography(FFA).At the same time,the changes of best corrected visual acuity(BCVA)before and after PRP were recorded and compared.Linear mixed-effects model was used to highlight differences for variables after adjusting for sex,age,and axial length.Results:Compared to baseline,there were no statistical differences in macular and peripapillary VD and SFCT following PRP(P>0.05).Macular thickness significantly increased at 1 month,3 months and 6 months after PRP(P=0.005,P=0.025,P=0.042,respectively),while peripapillary RNFL and GCC thickness significantly increased at 1 month postoperatively(P<0.001,P=0.006,respectively).Global loss volume(GLV)and focal loss volume(FLV)significantly decreased at the same timepoint(P<0.001,P=0.004,respectively).Regression of neovascularization after PRP was documented in 18 eyes(18/22,82%)in FFA images.Correspondingly,reduced area of neovascularization was clearly could also be observed on OCTA images.Conclusion:(1)OCT-EDI and OCTA can qualitatively observe and quantitatively analyze the microvascular,neural,and choroidal changes in patients with DR after PRP,and it is useful to evaluate the therapeutic efficacy of PRP.(2)The unchanged VD and thickness in macular and peripapillary area in the long-term postoperative period suggest that PRP may stabilize or relieve the microvascular and neural damage in eyes with severe NPDR and PDR.