Analysis Of Microvascular Abnormalities In Diabetic Retinopathy Using Optical Coherence Tomography Angiography

PURPOSE.Based on the latest research on optical coherence tomography angiography(OCTA),this study discussed the application of OCTA in the observation and analysis of retinal microvascular abnormalities and the treatment of DR patients.METHODS.Diabetes mellitus patients in ophthalmology and Endocrinology Department of the First Affiliated Hospital of Anhui Medical University and control group were collected.General ophthalmological examinations(vision,slit lamp examination,intraocular pressure examination),fundus examination after mydriasis,fundus photography and OCTA were completed in each eye.Patients with diabetic macular edema(DME)or proliferative DR were treated with intravitreal injection of Combercept and panretinal photocoagulation.The foveal avascular zone(FAZ)area,perimeter,acircularity index(AI)andvessel density within a 300-?m wide region of the FAZ(FD-300),parafoveal vessel density in the superficial capillary plexus(SCP)and deep capillary plexus(DCP)were collected in OCTA with the Angio-Retina mode.The blood flow density of radial peripapillary capillary(RPC)and the thickness of retinal nerve fiber layer(RNFL)in the peripapillary region were analyzed by OCTA scanningwith the Angio-Disc mode.The data were assessed for normality using the Shapiro-Wilk test.All data are presented as the mean ± standard deviation,median and interquartile range,or percentages as appropriate.Differences between the categorical data were assessed using Chi-square test or Fisher's exact test.Differences in the data obtained were assessed using Student's t-test,analysis of variance(ANOVA),or the Wilcoxon rank test,depending on their distribution.Since not all variances of the groups are equal,the nonparametric Kruskal-Wallis with Bonferroni correction for multiple comparisons were used to compare values between groups.The Kendall tau correlation coefficient was used to examine correlations between the OCTA parameters and severity of DR.All the statistical analyses were performed using SPSS 23.0 software.All statistical tests were considered significant when the p-value was < 0.05.RESULTS.In the first part,we analyzed 59 cases of diabetic patients(93 eyes),including 31 eyes without diabetic retinopathy(No DR),34 eyes with mild to moderate the none proliferation stage of diabetic retinopathy(Mild DR group)and 28 severe stage non proliferation to the proliferation of diabetic retinopathy(Severe DR group),in addition,there are 31 normal controls(Control group).There was no statistically significant difference in FAZ area between the four groups(P=0.162),FAZ circumference(P= 0.010)and AI(P <0.001).There was a correlation between AI and DR severity increase(p=0.010).Vessel density decreased significantly in FD-300,SCP and DCP(all p<0.001).The difference in vessel density of DCP between the control group and the No DR group was statistically significant(P=0.027).There was a significant correlation between vessel density and DR severity(P<0.001).In the second part,61 diabetic patients(97 eyes)were collected,including 36 eyes in the No DR group,29 eyes in the Mild DR group and 32 eyes in the Severe DR group,and 27 eyes in the Control group.The mean vessel density in RPC around the optic disc was significantly different between the four groups(p=0.000).The vessel density in RPC was closely related to DR severity(p=0.000),and decreased with DR aggravating.The differences in vessel density of nasal superior(NS),superior nasal(SN),nasal inferior(NI),inferior nasal(IN),inferior temporal(IT),temporal inferior(TI),temporal superior(TS),and superior temporal(ST)between the four groups were statistically significant(all p<0.001).There were significant correlations between DR severity and vessel density in all sectors(all p < 0.001)which decreased with DR aggravating.Among the four groups,the difference in average thickness of RNFL around the optic disc was statistically significant(p=0.015).There was no correlation between averagethickness of RNFL around optic disc and DR severity(p=0.085).The differences in RNFL thickness of NS,NI,IN,IT,TI,TS,and STbetween the four groups were statistically significant(p < 0.05),while the differences in RNFL thickness of SNbetween the four groups were not statistically significant(p > 0.05).Changes in RNFL thickness in the NS,IN,IT,TI and ST were correlated with DR severity(all p < 0.05),while changes in RNFL thickness in the NI,TS,SN were not correlated with DR severity(p > 0.05).In the third part,13 cases(16 eyes)withdiabetic macular edema(DME)were included.All eyes underwent Conbercept injection combined panretinal photocoagulation(PRP)The first visit was 2 weeks after the first injection of Conbercept,thesecond time visit was 1 month after the first Conbercept injection,the third time visit was 3 months after injection of Conbercept.All the best corrected visual acuity(BCVA),the FAZ and the foveal microcirculation parameters were collected before treatment and after treatment for analysis.BCVA of the first,second and third visits were improved.(all P < 0.05).There were no statistical differences in retinal thickness,FAZ area,perimeter,AI and vessel density between before and after treatment(all P > 0.05).In the fourth part,17 patients(20 eyes)with proliferative DR and neovascularization at the disc(NVD)underwent Conbercept injection combined with PRP.After routine ophthalmic examination and OCTA examination,eye data before treatment and 1 month after laser completion were collected for analysis.It was found that OCTA could clearly display the morphology of optic disc neovascularization,and the NVD area and Int Den gray value before and after the quantitative analysis showed statistically significant differences(all P < 0.05).CONCLUSIONS.OCTA can quantify the microcirculation in macular area and optic disc area of DR patients,and the vessel density in macular area and around optic disc of DR patients decreases with the disease progression.In addition,Parafoveal vessel density in the DCP after PAR might be a potential early biomarker of DR before appearance of clinically evident retinopathy and needs further investigation.Short-term anti-VEGF treatment did not aggravate the macular ischemia in DME patients.Quantitative information on NVD can be obtained with OCTA,which may be clinically useful in evaluating the therapeutic effect of treatments for NVD in PDR.