Analysis of retinal vasculature changes in indirect traumatic optic neuropathy using optic coherence tomography angiography

AIM:To assess the retinal vasculature alterations in indirect traumatic optic neuropathy(ITON)patients following craniofacial trauma by optic coherence tomography angiography(OCTA).METHODS:Patients diagnosed of monocular ITON were recruited from August 2016 to May 2020.OCTA was performed using the Angio Vue OCT-A system for two cube scans centered at the optic nerve head and fovea.OCTA data included thicknesses of peripapillary retinal nerve fiber layer(RNFL)and macular ganglion cell complex(GCC),as well as proportion of capillary perfusion and data were analyzed for correlation with post-injury timepoints:within 7,8-30,31-90,and 91-365d.RESULTS:A total of 73 ITON patients were studied.Significant thinning of RNFL and GCC layers and attenuation of microvascular perfusion were observed in ITON eyes as compared to contralateral unaffected eyes(for most of the analyzed sectors and quadrants,P<0.05).Without respect to surgical intervention and vision recovery,the decrease in retinal layer thicknesses and microvascular perfusion was time-dependent,and most significant within three months(P<0.001).CONCLUSION:ITON presents with time-dependent thinning of retinal layers and attenuation of microvasculature,indicating possible degeneration of retinal ganglion cells due to reduced retinal blood supply.

Automatic diagnosis of diabetic retinopathy using vision transformer based on wide-field optical coherence tomography angiography

Diabetic retinopathy(DR)is one of the major causes of visual impairment in adults with diabetes.Optical coherence tomography angiography(OCTA)is nowadays widely used as the golden criterion for diagnosing DR.Recently,wide-field OCTA(WF-OCTA)provided more abundant information including that of the peripheral retinal degenerative changes and it can contribute in accurately diagnosing DR.The need for an automatic DR diagnostic system based on WF-OCTA pictures attracts more and more attention due to the large diabetic population and the prevalence of retinopathy cases.In this study,automatic diagnosis of DR using vision transformer was performed using WF-OCTA images(12 mm×12 mm single-scan)centered on the fovea as the dataset.WF-OCTA images were automatically classified into four classes:No DR,mild nonproliferative diabetic retinopathy(NPDR),moderate to severe NPDR,and proliferative diabetic retinopathy(PDR).The proposed method for detecting DR on the test set achieves accuracy of 99.55%,sensitivity of 99.49%,and specificity of 99.57%.The accuracy of the method for DR staging reaches up to 99.20%,which has been proven to be higher than that attained by classical convolutional neural network models.Results show that the automatic diagnosis of DR based on vision transformer and WF-OCTA pictures is more effective for detecting and staging DR.

Aflibercept combined with triamcinolone acetonide in the treatment of diabetic macular edema:optical coherence tomography and optical coherence tomography angiography

AIM:To analyze the relationship between optical coherence tomography(OCT)and OCT angiography(OCTA)imaging in patients with diabetic macular edema(DME)who are treated with a combination of aflibercept and triamcinolone acetonide(TA).METHODS:A total of 76 eyes newly diagnosed DME were included in this study.They were randomly assigned to receive either aflibercept or a combination of aflibercept and TA.Injections once a month for a total of three injections.Central macular thickness(CMT),number of hyperreflective foci(HRF),height of subretinal fluid(SRF),and area of foveal avascular zone(FAZ)were evaluated using OCT and OCTA at baseline and after each monthly treatment.RESULTS:Both groups showed improvement in best corrected visual acuity(BCVA)and reduction in macular edema after treatment,and the difference in BCVA between the two groups was statistically significant after each treatment(P<0.05).The difference in CMT between the two groups was statistically significant after the first two injections(P<0.01),but not after the third injection(P=0.875).The number of HRF(1mo:7.41±8.25 vs 10.86±7.22,P=0.027;2mo:5.33±6.13 vs 9.12±8.61,P=0.034;3mo:3.58±3.00 vs 6.37±5.97,P=0.007)and height of SRF(1mo:82.39±39.12 vs 105.77±42.26μm,P=0.011;2mo:36.84±10.02 vs 83.59±37.78μm,P<0.01;3mo:11.57±3.29 vs 45.43±12.60μm,P<0.01)in combined group were statistically significant less than aflibercept group after each injection,while the area of FAZ showed no significant change before and after treatment in both groups.CONCLUSION:The combination therapy of aflibercept and TA shows more significant effects on DME eyes with decreased HRF and SRF.However,both aflibercept and combination therapy show no significant change in the area of FAZ.

Predictive visual field outcomes after optic chiasm decompressive surgery by retinal vessels parameters using optical coherence tomography angiography

AIM:To evaluate the predictive value of superficial retinal capillary plexus(SRCP)and radial peripapillary capillary(RPC)for visual field recovery after optic cross decompression and compare them with peripapillary nerve fiber layer(pRNFL)and ganglion cell complex(GCC).METHODS:This prospective longitudinal observational study included patients with chiasmal compression due to sellar region mass scheduled for decompressive surgery.Generalized estimating equations were used to compare retinal vessel density and retinal layer thickness preand post-operatively and with healthy controls.Logistic regression models were used to assess the relationship between preoperative GCC,pRNFL,SRCP,and RPC parameters and visual field recovery after surgery.RESULTS:The study included 43 eyes of 24 patients and 48 eyes of 24 healthy controls.Preoperative RPC and SRCP vessel density and pRNFL and GCC thickness were lower than healthy controls and higher than postoperative values.The best predictive GCC and pRNFL models were based on the superior GCC[area under the curve(AUC)=0.866]and the tempo-inferior pRNFL(AUC=0.824),and the best predictive SRCP and RPC models were based on the nasal SRCP(AUC=0.718)and tempo-inferior RPC(AUC=0.825).There was no statistical difference in the predictive value of the superior GCC,tempo-inferior pRNFL,and tempo-inferior RPC(all P>0.05).CONCLUSION:Compression of the optic chiasm by tumors in the saddle area can reduce retinal thickness and blood perfusion.This reduction persists despite the recovery of the visual field after decompression surgery.GCC,pRNFL,and RPC can be used as sensitive predictors of visual field recovery after decompression surgery.

Automated evaluation of parapapillary choroidal microvasculature in crowded optic discs:a controlled,optical coherence tomography angiography study

AIM:To compare superficial and deep vascular properties of optic discs between crowded discs and controls using optical coherence tomography angiography(OCT-A).METHODS:Thirty patients with crowded discs,and 47 control subjects were enrolled in the study.One eye of each individual was included and OCT-A scans of optic discs were obtained in a 4.5×4.5 mm^(2) rectangular area.Radial peripapillary capillary(RPC)density,peripapillary retinal nerve fiber layer(pRNFL)thickness,cup volume,rim area,disc area,cup-to-disc(c/d)area ratio,and vertical c/d ratio were obtained automatically using device software.Automated parapapillary choroidal microvasculature(PPCMv)density was calculated using MATLAB software.When the vertical c/d ratio of the optic disc was absent or small cup,it was considered as a crowded disc.RESULTS:The mean signal strength index of OCT-A images was similar between the crowded discs and control eyes(P=0.740).There was no difference in pRNFL between the two groups(P=0.102).There were no differences in RPC density in whole image(P=0.826)and peripapillary region(P=0.923),but inside disc RPC density was higher in crowded optic discs(P=0.003).The PPCMv density in the inner-hemisuperior region was also lower in crowded discs(P=0.026).The pRNFL thickness was positively correlated with peripapillary RPC density(r=0.498,P<0.001).The inside disc RPC density was negatively correlated with c/d area ratio(r=-0.341,P=0.002).CONCLUSION:The higher inside disc RPC density and lower inner-hemisuperior PPCMv density are found in eyes with crowded optic discs.

Retinal capillary plexus in Parkinson’s disease using optical coherence tomography angiography

AIM:To evaluate the alterations of the retinal microvasculature and foveal avascular zone in patients with Parkinson’s disease(PD)using optical coherence tomography angiography(OCT-A).METHODS:A retrospective study of PD patients examined in the Ophthalmology Department of the General Hospital of Athens,“Georgios Gennimatas”from March 2021 to March 2022 was conducted.Totally 44 patients with PD were included and 18 healthy controls were examined,hence a total of 124 eyes were enrolled in the study.The foveal and parafoveal superficial and deep capillary plexus vascular density(fSCP-VD,fDCP-VD,pSCP-VD,pDCP-CD)and foveal avascular zone(FAZ)were quantified with OCTA.Optical coherence tomography(OCT)was used to measure macular thickness.Our statistical analysis was conducted by using a mixed effect linear regression model.RESULTS:After adjustment for age and gender,the mean parafoveal superficial capillary plexus vascular density(pSCP-VD)and mean parafoveal deep capillary plexus vascular density(pDCP-VD)were significantly decreased in individuals with PD(P<0.001 in both)by-2.35(95%CI-3.3,-1.45)and-7.5(95%CI-10.4,-4.6)respectively.fSCP-VD and fDCP-VD didn’t approach statistical significance.The FAZ area and perimeter were significantly decreased(P<0.001 in both)by-0.1 mm^(2)(95%CI-0.13,-0.07)and-0.49 mm^(2)(95%CI-0.66,-0.32)respectively.Circularity didn’t approach statistical significance.Central retinal thickness(CRT)was significantly decreased in individuals with PD(P<0.001)by-23.1μm(95%CI-30.2,-16)and temporal retinal thickness(TRT)was decreased(P=0.025)by-11μm(95%CI-22,-1.5)while nasal retinal thickness(NRT)only approached statistical significance(P=0.066).CONCLUSION:The mean pSCP-VD,pDCP-VD,CRT and TRT are significantly decreased and FAZ is altered in individuals with PD.These findings can be potentially used as biomarkers for the diagnosis and evaluation of early PD.

Retinal microcirculation changes in prediabetic patients with shortterm increased blood glucose using optical coherence tomography angiography

BACKGROUND Retinal microcirculation alterations are early indicators of diabetic microvascular complications.Optical coherence tomography angiography(OCTA)is a noninvasive method to assess these changes.This study analyzes changes in retinal microcirculation in prediabetic patients during short-term increases in blood glucose using OCTA.AIM To investigate the changes in retinal microcirculation in prediabetic patients experiencing short-term increases in blood glucose levels using OCTA.METHODS Fifty volunteers were divided into three groups:Group 1[impaired fasting glucose(IFG)or impaired glucose tolerance(IGT)],Group 2(both IFG and IGT),and a control group.Retinal microcirculation parameters,including vessel density(VD),perfusion density(PD),and foveal avascular zone(FAZ)metrics,were measured using OCTA.Correlations between these parameters and blood glucose levels were analyzed in both the fasting and postprandial states.RESULTS One hour after glucose intake,the central VD(P=0.023),central PD(P=0.026),and parafoveal PD(P<0.001)were significantly greater in the control group than in the fasting group.In Group 1,parafoveal PD(P<0.001)and FAZ circularity(P=0.023)also increased one hour after glucose intake.However,no significant changes were observed in the retinal microcirculation parameters of Group 2 before or after glucose intake(P>0.05).Compared with the control group,Group 1 had a larger FAZ area(P=0.032)and perimeter(P=0.018),whereas Group 2 had no significant differences in retinal microcirculation parameters compared with the control group(P>0.05).Compared with Group 1,Group 2 had greater central VD(P=0.013)and PD(P=0.008)and a smaller FAZ area(P=0.012)and perimeter(P=0.010).One hour after glucose intake,Group 1 had a larger FAZ area(P=0.044)and perimeter(P=0.038)than did the control group,whereas Group 2 showed no significant differences in retinal microcirculation parameters compared with the control group(P>0.05).Group 2 had greater central VD(P=0.042)and PD(P=0.022)and a smaller FAZ area(P=0.015)and perimeter(P=0.016)than Group 1.At fasting,central PD was significantly positively correlated with blood glucose levels(P=0.044),whereas no significant correlations were found between blood glucose levels and OCTA parameters one hour after glucose intake.CONCLUSION A short-term increase in blood glucose has a more pronounced effect on retinal microcirculation in prediabetic patients with either IFG or IGT.

Repeatability,interocular correlation and agreement of optic nerve head vessel density in healthy eyes:a sweptsource optical coherence tomographic angiography study

AIM:To assess the repeatability,interocular correlation,and agreement of quantitative swept-source optical coherence tomography angiography(OCTA)optic nerve head(ONH)parameters in healthy subjects.METHODS:Thir ty-three healthy subjects were enrolled.The ONH of both eyes were imaged four times by a swept-source-OCTA using a 3 mm×3 mm scanning protocol.Images of the radial peripapillary capillary were analyzed by a customized Matlab program,and the vessel density,fractal dimension,and vessel diameter index were measured.The repeatability of the four scans was determined by the intraclass correlation coefficient(ICC).The most well-centered optic disc from the four repeated scans was then selected for the interocular correlation and agreement analysis using the Pearson correlation coefficient,ICC and Bland-Altman plots.RESULTS:All swept-source-OCTA ONH parameters exhibited certain repeatability,with ICC>0.760 and coefficient of variation(CoV)≤7.301%.The obvious interocular correlation was observed for papillary vessel density(ICC=0.857),vessel diameter index(ICC=0.857)and fractal dimension(ICC=0.906),while circumpapillary vessel density exhibited moderate interocular correlation(ICC=0.687).Bland-Altman plots revealed an agreement range of-5.26%to 6.21%for circumpapillary vessel density.CONCLUSION:OCTA ONH parameters demonstrate good repeatability in healthy subjects.The interocular correlations of papillary vessel density,fractal dimension and vessel diameter index are high,but the correlation for circumpapillary vessel density is moderate.

Evaluation of optic nerve head vessels density changes after phacoemulsification cataract surgery using optical coherence tomography angiography

·AIM:To evaluate optic nerve head(ONH)vessel density(VD)changes after cataract surgery using optical coherence tomography angiography(OCTA).·METHODS:This was a prospective observational study.Thirty-four eyes with mild/moderate cataracts were included.ONH scans were obtained before and 3mo after cataract surgery using OCTA.Radial peripapillary capillary(RPC)density,all VD,large VD and retinal nerve fiber layer thickness(RNFLT)in total disc,inside disc,and different peripapillary sectors were assessed and analyzed.Image quality score(QS),fundus photography grading and bestcorrected visual acuity(BCVA)were also collected,and correlation analyses were performed between VD change and these parameters.·RESULTS:Compared with baseline,both RPC and all VD increased in inside disc area 3mo postoperatively(from 47.5%±5.3%to 50.2%±3.7%,and from 57.87%±4.30%to 60.47%±3.10%,all P<0.001),but no differences were observed in peripapillary area.However,large VD increased from 5.63%±0.77%to 6.47%±0.72%in peripapillary ONH region(P<0.001).RPC decreased in inferior and superior peripapillary ONH parts(P=0.019,<0.001 respectively).There were obvious negative correlations between RPC change and large VD change in inside disc,superior-hemi,and inferior-hemi(r=-0.419,-0.370,and-0.439,P=0.017,0.044,and 0.015,respectively).No correlations were found between VD change and other parameters including QS change,fundus photography grading,postoperative BCVA,and postoperative peripapillary RNFLT.·CONCLUSION:RPC density and all VD in the inside disc ONH region increase 3mo after surgery in patients with mild to moderate cataract.No obvious VD changes are found in peripapillary area postoperatively.

In vivo quantification of human aqueous veins by enhanced depth imaging optical coherence tomography and optical coherence tomography angiography images

AIM:To investigate the aqueous vein in vivo by using enhanced depth imaging optical coherence tomography(EDI-OCT)and optical coherence tomography angiography(OCTA).METHODS:In this cross-sectional comparative study,30 healthy participants were enrolled.Images of the aqueous and conjunctival veins were captured by EDI-OCT and OCTA before and after water loading.The area,height,width,location depth and blood flow of the aqueous vein and conjunctival vein were measured by Image J software.RESULTS:In the static state,the area of the aqueous vein was 8166.7±3272.7μm^(2),which was smaller than that of the conjunctival vein(13690±7457μm^(2),P<0.001).The mean blood flow density of the aqueous vein was 35.3%±12.6%,which was significantly less than that of the conjunctival vein(51.5%±10.6%,P<0.001).After water loading,the area of the aqueous vein decreased significantly from 8725.8±779.4μm^(2)(baseline)to 7005.2±566.2μm^(2)at 45min but rose to 7863.0±703.2μm^(2)at 60min(P=0.032).The blood flow density of the aqueous vein decreased significantly from 41.2%±4.5%(baseline)to 35.4%±3.2%at 30min but returned to 45.6%±3.6%at 60min(P=0.021).CONCLUSION:The structure and blood flow density of the aqueous vein can be effectively evaluated by OCT and OCTA.These may become biological indicators to evaluate aqueous vein changes and aqueous outflow resistance under different interventions in glaucoma patients.

Changes of retinal vessel density in low to moderate myopic eyes with orthokeratology evaluated by optical coherence tomography angiography

AIM:To explore the effect of orthokeratology(OK)fitting on retinal vessel density in low to moderate myopia adolescents by using optical coherence tomography angiography.METHODS:Children aged 10 to 14y with a cycloplegic spherical equivalent refraction of−0.50 diopter(D)to−5.00 D and astigmatism with more than−1.50 D were recruited.The enrolled adolescents were divided into OK group and spectacle group.During regular followup,adolescents were measured respectively at pre-wear,1,3,and 6mo after treatment.The follow-up included uncorrected distance visual acuity(UDVA),axial length(AL),superficial capillary plexus density(SCPD),deep capillary plexus density(DCPD),central retinal thickness(CRT),foveal avascular zone area(FAZ-A),foveal avascular zone perimeter(FAZ-P)and foveal vessel density in a 300-μmwide region around foveal avascular zone(FD-300).The collected data were analyzed using statistical methods.RESULTS:By one month,SCPD significantly increased in the fovea and superior retina,and DCPD significantly increased inferiorly in OK group compared to spectacle group(P<0.05).By three months,there were significant increases in SCPD in the fovea and inferior retina,and DCPD in the parafovea,superior,and inferior retina in OK group(P<0.05),while the increase in SCPD and DCPD in the fovea were observed by six months(P<0.05).The FD-300 significantly increased at every follow-up in OK group compared to spectacle group(P<0.05).No significant differences in the CRT,FAZ-A and FAZ-P and FD-300 were observed between two groups(P>0.05).OK group showed a significant improvement in UDVA after wearing OK,compared to spectacle group(P<0.01),while the AL did not show a significant difference between two groups(P>0.05).CONCLUSION:Short-term OK worn can increase local retinal vessel density in adolescents with low-to-moderate myopia.

Optical coherence tomography angiography for macular microvessels in ischemic branch retinal vein occlusion treated with conbercept:predictive factors for the prognosis

AIM:To evaluate the predicative factors of visual prognosis using optical coherence tomography angiography(OCTA)in ischemic branch retinal vein occlusion(BRVO)patients with macular edema(ME)after anti-vascular endothelial growth factor(VEGF)treatment.METHODS:In this retrospective analysis,data from 60 patients(60 eyes)with a definite diagnosis of ischemic BRVO with ME by fundus fluorescein angiography(FFA)were studied.The eyes with ME according to spectral domain optical coherence tomography(SD-OCT)underwent intravitreal conbercept(IVC)and 3+pro re nata(PRN)regimen.The injection times were recorded.Two weeks after injection,fundus laser photocoagulation was performed in the non-perfusion area of the retina.The patients were followed up once a month for 6mo.The bestcorrected visual acuity(BCVA),foveal avascular zone(FAZ),and A-circularity index(AI),at 6mo and the baseline were compared.RESULTS:All patients showed significant improvement in BCVA from 0.82±0.32 to 0.39±0.11 logMAR(P<0.001).The mean central macular thickness(CMT)significantly decreased from 476.22±163.54 to 298.66±109.23μm.Both the FAZ area and AI at 6mo were significantly higher than those at the baseline:the FAZ area increased(0.38±0.02 vs 0.39±0.02 mm^(2),P<0.05);the AI increased(1.27±0.02 vs 1.31±0.01,P=0.000).The baseline BCVA showed a significantly positive correlation with the baseline FAZ area,FAZ perimeter(PERIM)and AI,final visual gain(FVG)and injection times,respectively(P<0.001).FVG showed a significantly negative correlation with the FAZ area,PERIM,AI and injection times,but a significantly positive correlation with vessel densities(VDs)300μm area around FAZ(FD-300;P<0.001).Injection times was positively correlated with the baseline FAZ area,and AI,but inversely correlated with the baseline FD-300(P<0.001).However macular ischemia was noted in 5 cases during follow-up.CONCLUSION:Using OCTA to observe macular ischemia and quantify parameters can better predict the final visual prognosis of patients before treatment.The changes in FAZ parameters may influence the visual prognosis and injection times.

Epiretinal membrane related vascular changes in diabetic eyes evaluated with optical coherence tomography angiography

AIM:To evaluate the retinochoroidal microvascular circulation and anatomical structure of diabetic and nondiabetic patients with epiretinal membrane(ERM)with the help of optical coherence tomography angiography(OCT-A)and compare them with healthy control subjects.METHODS:In this prospective,cross-sectional study,a total of 165 eyes were evaluated,including 50 eyes of patients with diabetic ERM,54 eyes of idiopathic ERM(iERM)patients,and 61 eyes of healthy controls.Macula and disc angiography was performed by OCT-A.Macular vessel density(VD)ratio was evaluated by dividing the VD of the foveal region by the VD of the parafoveal region.Statistical calculations were evaluated at the 95%confidence interval.RESULTS:Macula superficial VD values of ERM cases were lower than that in the control group,while foveal VD was higher in ERM cases.Macula deep VD values of ERM cases were lower in all quadrants,except the fovea.The width of the foveal avascular zone(FAZ)area was significantly lower in the ERM groups,and the FAZ width was lowest in iERM group.Macula superficial VD ratio was significantly higher in the ERM groups,but there was no significant difference between ERM groups.Macula deep VD ratio was significantly higher in the iERM group than in the control group.CONCLUSION:Diabetic and idiopathic ERMs differ in their mechanism of formation and clinical presentation,as well as their effect on retinal vascular structures.If the relationship of increase of retinal thickness with vascular integrity can be demonstrated with OCT-A,then,OCT-A can be used as a guide for ERM prognosis.

Optical coherence tomography angiography characteristics of exudative and non-exudative treatmentnaive pachychoroid neovasculopathy

AIM:To describe the optical coherence tomography angiography(OCTA)characteristics of exudative and nonexudative treatment-naïve pachychoroid neovasculopathy(PNV).METHODS:Thirty-five patients with exudative treatmentnaïve PNV and 13 with non-exudative treatment-naïve PNV between March 2020 and December 2021 were included.All patients underwent ophthalmologic examination,including fluorescein angiography(FA),indocyanine green angiography(ICGA),spectral-domain OCT,and OCTA.The clinical data of the patients were retrospectively analyzed.RESULTS:The study included 51 eyes from 46 patients,of whom 33(71.7%)were male.The central macular thickness(CMT)in the exudative PNV group was significantly higher than that in the non-exudative PNV group(383.97±132.16μm vs 213.13±51.63μm;P<0.001).The maximum height of flat irregular pigment epithelial detachments(FIPED)was 45.40±11.86μm in the non-exudative PNV group,significantly lower than the 71.58±20.91μm(P<0.001)in the exudative PNV group.The area of PNV of the non-exudative PNV group was,significantly larger than that of the exudative PNV group(1.06±0.84 mm2 vs 0.63±0.80 mm2,P=0.016).There was a significant difference in PNV morphology between the two groups(P<0.001).Multivariate logistic regression analysis found that the maximum height of FIPED(OR=1.156,95%CI:1.019-1.312;P=0.024)and microvascular branches(OR=69.412,95%CI:3.538-1361.844;P=0.005)were independent predictors of PNV activity.CONCLUSION:The OCTA imaging finds that there are significant differences in CMT,maximum height of FIPED,PNV area,and morphology of exudative PNV and non-exudative PNV groups.OCTA can accurately identify the clinical and imaging features of exudative and nonexudative treatment-naïve PNV,and distinguish PNV activity.

Retinal thickness and vascular parameters using optical coherence tomography in Alzheimer's disease:a meta-analysis

Examining the retinal tissue has the potential to provide a unique method and technique to quantify Alzheimer’s disease-related changes in participants at various stages of the disease.In this metaanalysis,we aimed to investigate the association of various optical coherence tomography parameters with Alzheimer’s disease and whether retinal measurements can be used to diffe rentiate between Alzheimer’s disease and control subjects.Scientific databases including Google Schola r,Web of Science,and PubMed were systematically searched for published articles that evaluated retinal nerve fiber layer thickness and retinal microvascular network in Alzheimer’s disease and control subjects.Seventy-three studies(5850 participants,including 2249 Alzheimer’s disease patients and 3601controls) were included in this meta-analysis.Relative to controls,Alzheimer’s disease patients had a significantly lower global retinal nerve fiber layer thickness(standardized mean difference [SMD]=-0.79,95% confidence intervals [CI]:-1.03 to-0.54,P <0.00001) as well as each quadrant being thinner in Alzheimer’s disease versus controls.Regarding macular paramete rs,values measured by optical coherence tomography were significantly lower in Alzheimer’s disease than controls for macular thickness(pooled SMD:-0.44,95% CI:-0.67 to-0.20,P=0.0003),foveal thickness(pooled SMD=-0.39,95% CI:-0.58 to-0.19,P <0.0001),ganglion cell inner plexiform layer(SMD=-1.26,95% CI:-2.24 to-0.27,P=0.01) and macular volume(pooled SMD=-0.41,95% CI-0.76 to-0.07,P=0.02).Analysis using optical coherence tomography angiography parameters revealed mixed results between Alzheimer’s disease and controls.Superficial vessel density(pooled SMD=-0.42,95% CI:-0.68 to-0.17,P=0.0001) and deep vessel density(pooled SMD=-0.46,95% CI:-0.75 to-0.18,P=0.001) were found to be thinner in Alzheimer’s disease patients whereas the foveal avascular zone(SMD=0.84,95% CI:0.17-1.51,P=0.01) was larger in controls.Vascular density and thickness of various retinal laye rs were decreased in Alzheimer’s disease patients compared to controls.Our results provide evidence for optical coherence tomography technology having the potential to detect retinal and microvascular changes in patients diagnosed with Alzheimer’s disease and aid in monito ring and early diagnosis methods.

Foveal avascular zone area and parafoveal vessel density measurements in different stages of diabetic retinopathy by optical coherence tomography angiography

AIM：To investigate foveal avascular zone（FAZ）and parafoveal vessel densities（PRVD）by means of optical coherence tomography angiography（OCTA）in diabetic patients with or without diabetic retinopathy（DR）and to assess the reproducibility of FAZ and PRVD measurements.METHODS：Sixty diabetic patients（60 eyes）with different stage of DR（graded according to the International Clinical Severity Scale for DR）and 20 healthy subjects underwent FAZ area and PRVD measurements using OCTA by two experienced examiners.FAZ area in all patients was also assessed using fluorescein angiography（FA）.RESULTS：In subject with proliferative DR and with moderate-severe non proliferative DR,FAZ area was significantly increased compared to healthy controls（P=0.025 and P=0.050 respectively measured with OCTA and P=0.025 and P=0.048 respectively measured with FA）.OCTA showed significantly less inter-observer variability compared to FA.Concordance correlation coefficient（CCC）for FAZ area measurements was 0.829（95%CI：0.736-0.891）P〈0.001 with FA and 1.000（95%CI：0.999-1.000）P〈0.001with OCTA.CCC was 0.834（95%CI：0.746-0.893）P〈0.001and 0.890（95%CI：0.828-0.930）P〈0.001 for parafoveal superficial and deep vessel density measurements,respectively.CONCLUSION：OCTA shows progressive increase of FAZ area and reduction of PRVD in both superficial and deep plexus at increasing DR severity.FAZ area and PRVD measurements using OCTA are highly reproducible.

Optical coherence tomography angiography of optic disc perfusion in non-arteritic anterior ischemic optic neuropathy

AIM：To compare the optic disc blood flow of non-arteritic ischemic optic neuropathy（NAION）eyes with normal eyes.METHODS：The optic disc blood flow densities of diagnosed non-acute phase NAION eyes（21 eyes,14 individuals）and normal eyes（19 eyes,12 individuals）were detected via Optovue optical coherence tomography angiography（OCTA）.The optic disc blood flow was measured via Image J software.Correlations between optic disc perfusion and visual function variables were assessed by linear regression analysis.RESULTS：The average percentage of the optic disc nonperfusion areas in the non-acute phase NAION patients（17.84%±6.18%）was increased,when compared to the normal control eyes（8.61%±1.65%）,and the difference was statistically significant（P〈0.01）.Moreover,there was a proportional correlation between the visual field mean defect（MD）and the optic disc non-perfusion area percentage,and the relationship was statistically significant（t=3.65,P〈0.01,R2=0.4118）.In addition,the critical correlation between the best corrected visual acuity（BCVA）and the optic disc non-perfusion area percentage was statistically significant（t=4.32,P〈0.01,R2=0.4957）.CONCLUSION：The optic disc non-perfusion area percentages detected via OCTA in NAION eyes were significantly increased when compared with the normal eyes.Both the BCVA and MD were correlated with the optic disc flow detected,revealing that OCTA may be valuable in the diagnosis and estimation of NAION.

Repeatability and Reproducibility of Quantitative Assessment of the Retinal Microvasculature Using Optical Coherence Tomography Angiography Based on Optical Microangiography

Objective The aim of this study was to determine the repeatability and reproducibility of optical coherence tomography angiography（OCTA） based on optical microangiography（OMAG） measurements of macular vessels in normal eyes. Methods In this prospective cohort study, 40 eyes of 40 healthy volunteers underwent repeated OCTA（Cirrus HD-OCT 5000 angiography system, Carl Zeiss Meditec, Inc.） scans on two separate visit days. On each visit day, the eyes were scanned three times. The following parameters were used to quantitatively describe the OCTA images of the superficial vascular network： vessel area density（VAD）, vessel skeleton density（VSD）, vessel diameter index（VDI）, vessel perimeter index（VPI）, vessel complexity index（VCI）, flux, and foveal avascular zone（FAZ）. Coefficient of variation（CV） and intraclass correlation coefficient（ICC） were calculated for evaluating intravisit and intervisit repeatability, as well as interobserver reproducibility. Results The measurements showed high repeatability [CVs ≤ 4.2%（intravisit） and ≤ 4.6%（intervisit）] and interobserver reproducibility（ICCs ≥ 0.923） for all parameters. Conclusion This study demonstrated good repeatability and reproducibility of OCTA based on OMAG for the measurement of superficial vessel parameters in normal eyes.

Application of optical coherence tomography angiography in assessment of posterior scleral reinforcement for pathologic myopia

AIM： To investigate the effect of posterior scleral reinforcement （PSR） on circulation of pathologic myopia eyes with posterior staphyloma by optical coherence tomography angiography （OCTA）.METHODS： The study included 30 pathologic myopia eyes with posterior staphyloma which underwent PSR （PSR group） for 6 to 18mo ago, and 30 age and myopia matched eyes without PSR surgery as control group. Macular, choriocapillaris and radial peripapillary capillary （RPC） flow density were measured by OCTA, and the measurements were compared between groups. RESULTS： OCTA found no significant differences in macular flow density between PSR and control groups. For the superficial flow, whole enface flow density （WED）, fovea density （FD）, and parafoveal density （PD） were 46.55%±5.19% vs 47.29%±4.12% （P=0.542）, 31.45%±6.35% vs 31.17%±4.48% （P=0.841）, and 48.82%±5.66% vs 49.21%±4.15% （P=0.756） in PSR and control groups, respectively. For the deep flow, WED, FD, and PD were 52.07%±5.78% vs 53.95%±4.62% （P=0.168）, 29.62%±6.55% vs 29.50%±6.38% （P=0.940）, and 56.93%±6.17% vs 58.15%±5.13% （P=0.407） in PSR and control groups, respectively. The choriocapillary flow density was 61.18±3.25% in PSR group vs 60.88%±2.56% in control group （P=0.692）. Also, OCTA found no significant differences in RPCs flow density between PSR and control groups. The optic disc WED, inside disc flow density and peripapillary flow density were 48.47%±4.77% vs 48.11%±4.57% （P=0.813）, 45.47%±11.44% vs 46.68%±9.02% （P=0.709）, 54.32%±5.29% vs 52.47%±6.62% （P=0.349） in PSR and control groups, respectively.CONCLUSION： OCTA provides a non-invasive and quantitative approach for monitoring macular and papillary blood flow in pathologic myopia. PSR can not improve but may maintain the circulation of pathologic myopia eyes with posterior staphyloma.

Optical coherence tomography angiography assessment of 577 nm laser effect on severe non-proliferative diabetic retinopathy with diabetic macular edema

AIM:To quantitatively evaluate the effect of the combined use of 577-nm subthreshold micropulse macular laser(SML)and multi-point mode pan retinal laser photocoagulation(PRP)on severe non-proliferative diabetic retinopathy(NPDR)with central-involved diabetic macular edema(CIDME)using optical coherence tomography angiography(OCTA).METHODS:In this observational clinical study,86 eyes of 86 NPDR patients with CIDME who underwent SML and PRP treatment were included.Images were obtained 1 d before laser and post-laser(1 d,1 wk,1,3,and 6 mo)using AngioV ue software 2.0.Best corrected visual acuity(BCVA,LogM AR),foveal avascular zone area(FAZ),choriocapillary flow area(Ch F),parafoveal vessel density(PVD),capillary density inside disc(CDD),peripapillary capillary density(PCD),macular ganglion cell complex thickness(m GCCT),central macular thickness(CMT),and subfoveal choroidal thickness(ChT)were compared between pre-and post-laser treatment.RESULTS:BCVA remained stable during 6 mo postlaser therapy(pre-laser vs 6 mo post-laser:0.53±0.21 vs 0.5±0.15,P>0.05).PVD,ChF,ChT,CMT,and mGCCT significantly increased 1 d post-laser therapy[pre-laser vs 1 d post-laser:superficial PVD(%),40.51±3.42 vs 42.43±4.68;deep PVD(%),42.66±3.67 vs 44.78±4.52;ChF,1.72±0.21 vs 1.9±0.12 mm^2;ChT,302.45±69.74 vs 319.38±70.93μm;CMT,301.65±110.78 vs 320.86±105.62μm;m GCCT,105.71±10.72 vs 115.46±9.64μm;P<0.05].However,PVD,ChF and ChT decreased to less than baseline level at 6 mo postlaser therapy(pre-laser vs 6 mo post-laser:superficial PVD(%),40.51±3.42 vs 36.32±4.19;deep PVD(%),42.66±3.67 vs 38.76±3.74;Ch F,1.72±0.21 vs 1.62±0.09 mm^2;Ch T,302.45±69.74 vs 289.61±67.55μm;P<0.05),whereas CMT and mG CCT decreased to baseline level at 6 mo postlaser therapy(CMT,301.65±110.78 vs 297.77±90.23μm;m GCCT,105.71±10.72 vs 107.05±11.81μm;P>0.05).Moreover,FAZ continuously increased while CDD and PCD continuously decreased in 6 mo after laser therapy.CMT and ChT had a significant positive correlation with ChF and PVD in most post-laser stages.CONCLUSION:During a 6-month follow-up period after combined use of SML and PRP therapy,BCVA remained stable and there was a decreased trend in macular edema.Blood flow increased at 1 d post-laser therapy and reduced at 6 mo post-laser therapy.