Measurement Of Retinal Vascular Density And Choroid Microvasculature Dropout In Primary Angle Closure Glaucoma By OCTA

Objective: To investigate whether the retinal vascular density of the papilla in primary angle closure glaucoma(PACG)is lower than in normal eyes.Calculate the incidence of choroidal microvasculature dropout(CMvD)in PACG patients.And explore the relationship between extent and location of CMvD and retinal nerve fiber layer(RNFL)defect.And assess the association of CMvD and visual field injury degree.Methods: In this study,55 patients(55 eyes)with primary angle closure glaucoma and30 normal people(30 eyes)with roughly matched age and sex ratio were selected from Shantou International Eye Center from December 2019 to April 2022.After obtaining their informed consent,they underwent detailed ophthalmic examination,including best corrected visual acuity,intraocular pressure measurement,slit lamp fundus examination,OA-2000 ocular biological parameters measurement.The thickness of RNFL was measured by optical coherence tomography(OCT).The each layer vascular images of the papillary area were obtained from optical coherence tomography angiography(OCTA).1.Evaluate the normality of continuous variable data by Shapiro Wilk test.2.The general data,circumpapillary vascular density,RNFL and visual field injury parameters of 55 PACG eyes and 32 normal eyes were compared by independent t-test or Mann-Whitney test,and the differences of continuous variable between PACG patients with or without CMvD.3.Chi square test was used to compare the differences of categorical variables in PACG patients.4.Kappa coefficient,intraclass correlation coefficient(ICC)and Bland-Altman diagram were used to evaluate the consistency of the two observers’ measurement for the existence,range and location of CMvD in OCTA.5.Use binary logistic regression to count the factors that may be related to CMvD and establish the prediction model.Result: Except for the nasal side,the overall mean RNFL thickness of the optic disc in PACG eyes(47.14um±5.63um)and the RNFL thickness in other quadrants were significantly lower than those of normal eyes(p<0.001).The overall mean circumpapillary vessel density(cpVD)of patients with PACG(47.14%±5.63%)and the vascular density of each quadrant were lower than those of normal eyes(54.60%±2.50%)(P < 0.001).There was good agreement between the two observers for the detection of CMvD(Kappa=0.915).The incidence of CMvD in 55 PACG eyes was 47.3%.None of the normal eyes developed CMvD.The visual field mean deviation(MD)(-17.1d B±8.9d B)and pattern standard deviation(PSD)(8.1d B±3.4d B)of the group with CMvD showed a worse data than MD(-10.3d B±9.2d B)and PSD(6.1d B±3.7d B)of the group without CMvD(p < 0.05).Except for the nasal side,the mean RNFL thickness of the optic disc(68.1um±20.8um)and the other three quadrants of the group with CMvD were significantly lower than those of the group without CMvD(P<0.001).Similarly,cpVD in the group with CMvD(44.2% ± 4.9%)was also lower than that in the group without CMvD(49.8% ± 5.0%)(P < 0.05).The ICC for inter-observer reliability was 0.987(95% CI = 0.975–0.993)and 0.941(95%CI = 0.882–0.970)for the extent and location of the CMvD defect.For the extent and location of the RNFL defect,they were 0.999(95%CI=0.999-1.000)and 0.997(95%CI=0.994-0.998).Between CMvD and RNFL defects,the extent and location of CMvD was in good agreement with that of RNFL defects(circumferential extent:P=0.301;location: P=0.537,paired samples t-test).Logistic regression statistics showed that only RNFLt was statistically significant in the prediction model.For every1 um decrease in RNFLt,the incidence of CMvD increased by 4.5%.Conclusion: Compared with patients in PACG group,cpVD in normal group was significantly decreased.CMvD was detected in nearly half of the patients in the PACG group,and CMvD was not detected in the normal control group.Visual field injury was more significant in patients with CMvD than in patients without CMvD,and RNFL thickness and cpVD were also lower than those without CMvD.The extent and location of the CMvD were highly consistent with that of the RNFL defect.The results of this study suggest that choroidal microvasculature dropout and glaucomatous optic nerve injury are highly correlated.