Foveal Avascular Zone Area Measurements Research Articles

Foveal avascular zone area measurement in diabetic patients: Superficial, deep or combined retinal vascular complex?

PurposeTo compare differences in the foveal avascular zone (FAZ) area, measured in the Superficial Vascular Complex (SVC), Deep Vascular Complex (DVC) and a combined analysis of both (SDVC), using two Spectral Domain OCT angiography (OCT-A) protocols, High Speed (HS) and High Resolution (HR). MethodsA total of 26 eyes of diabetic patients, with and without macular oedema, were examined with two different fovea centered OCT-A volume scans. The two protocols were HS and HR volume scans, and the foveal avascular zone was manually measured in the SVC, DVC, and SDVC slabs by two masked investigators. Inter and intraoperator variability was analysed using Intraclass Correlation Coefficient (ICC) and differences were compared between the HR and HS acquisitions throughout the different vascular slabs. ResultsIntraoperator variability was low in all slabs (ICC > 0.9) and interoperator variability was lower for HR (ICC 0.835–0.911) compared to HS (ICC between 0.604 and 0.865). Comparing HS and HR measurements for the same slab, the correlation was only moderate in SVC and DVC (ICC was 0.640 and 0.568 respectively) but was good in the SDVC (ICC = 0.823). FAZ area measurement in SDVC also showed the smallest bias (mean difference 0.009 mm2) and the narrowest limits of agreement (−0.175 to 0.193 mm2). ConclusionsEven in cases of diabetic macular oedema, when measuring the FAZ area, the reproducibility was better between HS and HR protocols when using the SDVC slab, compared to the SVC or DVC slabs alone. Further studies should evaluate the use of the combined SDVC slab for the FAZ assessment, compared to the SVC and DVC slabs alone, in the detection and progression of different retinal diseases.

Intrasession Repeatability of OCT Angiography Parameters in Neurodegenerative Disease.

To assess the intrasession repeatability of macular OCT angiography (OCTA) parameters in Alzheimer's disease (AD), mild cognitive impairment (MCI), Parkinson's disease (PD), and normal cognition (NC). Cross sectional study. Patients with a clinical diagnosis of AD, PD, MCI, or NC were imaged. Images with poor quality and of those with diabetes mellitus, glaucoma, or vitreoretinal disease were excluded from analysis. All participants were imaged using the Zeiss Cirrus HD-5000 with AngioPlex (Carl Zeiss Meditec, Software Version 11.0.0.29946) and repeat OCTA images were obtained for both eyes. Perfusion density (PFD), vessel density (VD), and Foveal avascular zone (FAZ) area were measured from 3×3 mm and 6×6 mm OCTA images centered on the fovea using an ETDRS grid overlay. Intraclass correlation coefficients were used to quantify repeatability of PFD, VD, and FAZ area measurements obtained from imaging. 3×3 mm scans of 22 AD, 40 MCI, 21 PD, and 26 NC participants and 6×6 mm scans of 29 AD, 44 MCI, 29 PD, and 30 NC participants were analyzed. Repeatability values ranged from 0.64 (0.49-0.82) for 6×6 mm PFD in AD participants to 0.87 (0.67-0.92) for 3×3 mm PFD in AD participants. No significant differences were observed in repeatability between NC participants and those with neurodegenerative disease. Overall, similar OCTA repeatability was observed between NC participants and those with neurodegeneration. Regardless of diagnostic group, macular OCTA metrics demonstrated moderate to good repeatability. The authors have no proprietary or commercial interest in any materials discussed in this article.

Correcting magnification error in foveal avascular zone area measurements of optical coherence tomography angiography images with estimated axial length

BackgroundTo generate and validate a method to estimate axial length estimated (ALest) from spherical equivalent (SE) and corneal curvature [keratometry (K)], and to determine if this ALest can replace actual axial length (ALact) for correcting transverse magnification error in optical coherence tomography angiography (OCTA) images using the Littmann-Bennett formula.MethodsData from 1301 participants of the Raine Study Gen2-20 year follow-up were divided into two datasets to generate (n = 650) and validate (n = 651) a relationship between AL, SE, and K. The developed formula was then applied to a separate dataset of 46 participants with AL, SE, and K measurements and OCTA images to estimate and compare the performance of ALest against ALact in correcting transverse magnification error in OCTA images when measuring the foveal avascular zone area (FAZA).ResultsThe formula for ALest yielded the equation: ALest = 2.102K − 0.4125SE + 7.268, R2 = 0.794. There was good agreement between ALest and ALact for both study cohorts. The mean difference [standard deviation (SD)] between FAZA corrected with ALest and ALact was 0.002 (0.015) mm2 with the 95% limits of agreement (LoA) of − 0.027 to 0.031 mm2. In comparison, mean difference (SD) between FAZA uncorrected and corrected with ALact was − 0.005 (0.030) mm2, with 95% LoA of − 0.064 to 0.054 mm2.ConclusionsALact is more accurate than ALest and hence should be used preferentially in magnification error correction in the clinical setting. FAZA corrected with ALest is comparable to FAZA corrected with ALact, while FAZA measurements using images corrected with ALest have a greater accuracy than measurements on uncorrected images. Hence, in the absence of ALact, clinicians should use ALest to correct for magnification error as this provides for more accurate measurements of fundus parameters than uncorrected images.

Area of the foveal avascular zone in patients with refractive errors

To investigate the dependence of the area of the foveal avascular zone (FAZ) on axial eye length (AL) and to develop a feasible method for correcting this dependence. The study involved 209 patients over the age of 18 years (209 eyes), of them 52 patients with AL of 20-22 mm (hyperopia group), 60 patients with AL of 25.5-28.5 mm (myopia group) and 97 patients with AL of 22.5-24.5 mm (emmetropia group). Optical coherence tomography angiography (OCTA) examination was performed on Cirrus HD-OCT 5000 with AngioPlex («Carl Zeiss Meditec», Germany). FAZ area was corrected using the Littmann-Bennett formula modified by A.A. Shpak and M.V. Korobkova. FAZ area values both in emmetropic patients and in patients with refractive errors varied over a very wide range. Before correction, AL had a significant influence on the FAZ area (mm2), which compared to the emmetropia group (0.27±0.09) was significantly reduced in the myopia group (0.21±0.07; p<0.000) and increased in the hyperopia group (0.31±0.11; p=0.015). The corrected FAZ area values did not differ in the compared groups. After correction the FAZ area decreased on average by 19% in the hyperopia group and increased by 25% in the myopia group. A chart and an Excel (Microsoft)/LibreOffice Calc program have been developed for correction of the FAZ area depending on the AL. Refractive errors, especially high-degree ones, have a significant effect on the FAZ area. This study proposes an original chart and a calculation program for correct interpretation of FAZ area measurements in patients with refractive errors, providing an accessible and quick way to assess the obtained results.

Assessment of the retinal vasculature in healthy Chinese preschool children aged 4\u20136\u2009years old using optical coherence tomography angiography

PurposeTo establish normal parameters of macular and optic disc vasculature by optical coherence tomography angiography (OCTA) in healthy preschool children aged 4–6 years old in China. OCTA reflects retinal metabolism and development in children at these ages and could be used clinically and in future studies to aid diagnosis and prediction of retinal abnormalities and developmental stagnation.MethodsIn this cross-sectional study, we measured foveal, parafoveal, and perifoveal vessel density in the superficial capillary plexus (SCP); the deep capillary plexus (DCP), the foveal avascular zone (FAZ), and the radial capillary peripapillary (RPC) in the optic disc using investigational spectral-domain OCTA. The magnification effect of the FAZ area and microvasculature measurements was corrected by Littman and the modified Bennett formula.ResultsA total of 242 eyes (116 males and 126 females, 5.31 ± 0.73 years) were recruited for the analysis. The mean macular vessel density was 48.10 ± 2.92% and 48.74 ± 6.51% in the SCP and the DCP, respectively. The RPC vessel density was 47.17 ± 2.52%, 47.99 ± 4.48%, and 48.41 ± 3.07% in the whole image, inside disc, and peripapillary, respectively; and the mean FAZ area was 0.28 ± 0.11 mm2. A significant difference between male and female participants was found in the retinal vasculature (DCP, SCP, and RPC). None of these parameters were significantly different in age (P > 0.05), except that DCP slightly increased with aging. The right and left eyes had good consistency in the parameters of the macula and optic disc.ConclusionsOur study establishes the macular and optic disc OCTA reference values in 4- to 6-year-old healthy preschool children. They may be used in longitudinal OCTA studies and clinical applications.

Macular and peripapillary microvasculature after dexamethasone injection in diabetic macular edema.

To evaluate the microvascular changes in the macular and peripapillary area after intravitreal dexamethasone implant in diabetic macular edema (DME). We included 31 eyes of 31 patients treated with a single dose dexamethasone implant for DME. All subjects underwent swept-source optical coherence tomography (OCT) and OCT angiography imaging before (T0), and one month (T1), two months (T2), and four months (T4) after dexamethasone injection. The foveal avascular zone (FAZ) area of superficial and deep capillary plexus (SCP and DCP) was calculated by delineating the FAZ border using the measurement tool of the device. The vessel density (VD) of SCP and DCP and choriocapillaris (CC) in the macular and peripapillary area were automatically calculated. There was an insignificant reduction in FAZ area measurements of SCP after dexamethasone injection in DME patients (p = 0.846). The FAZ area of DCP were significantly smaller compared to T0 measurements at T1, T2, and T4 (p = 0.013, p = 0.031, and p = 0.029, respectively). The mean average parafoveal VD measurements were significantly decreased after dexamethasone injection in SCP and DCP (p = 0.004, p = 0.005). The peripapillary VD in retinal capillary plexuses and choriocapillaris showed no significant difference after dexamethasone injection. Intravitreal dexamethasone leads to a significant FAZ area decrease in DCP with a reduction in parafoveal VD measurements. In addition, no significant VD changes were observed in the peripapillary area after dexamethasone. These findings indicate that dexamethasone may improve macular ischemia with no significant effects on peripapillary microvasculature in DME patients.

The predictive value of ectopic inner retinal layer staging scheme for idiopathic epiretinal membrane: surgical results at 12 months.

To assess the effect of ectopic inner foveal layers (EIFL) based staging scheme, foveal avascular zone (FAZ) alterations and other microstructural optical coherence tomography (OCT) findings on visual function for patients undergoing idiopathic epiretinal membrane (iERM) surgery. In this retrospective study, patients who underwent 27 G pars plana vitrectomy (PPV) for idiopathic ERM with a minimum follow-up of 12 months were included. Preoperative and postoperative OCT scans, FAZ area measurements on en face OCT angiography images and mean retinal sensitivity (MRS) using microperimetry were recorded in all cases. The correlation of FAZ area, EIFL and other OCT parameters with preoperative and postoperative best-corrected visual acuity (BCVA) was analysed. In all, 112 eyes of 112 patients were included. Visual acuity improvement was statistically significant in all four stages; however, differences between Stages 2, 3 and 4 ERMs remained significant (p < 0.05). The presence and thickness of the EIFL was associated with worse baseline (p = 0.013; p = 0.005, respectively) and final (p < 0.001 for both) BCVA. The presence of cystoid macular oedema was associated with worse BCVA at baseline (p = 0.027) and postoperative month-6 (p = 0.04). The mean FAZ area was significantly reduced in all stages of ERM compared with the fellow eyes (p < 0.05 for all). Postoperative retinal sensitivity improvement was statistically significant in Stage 1 and Stage 2. The presence of EIFL is an independent predictor of worse postoperative BCVA. Accordingly, despite significant BCVA improvements in all stages of ERM, visual acuity gain remains limited in eyes with Stage 3 and Stage 4 ERM.

Foveal avascular zone area measurements in a normal Egyptian population using Heidelberg optical coherence tomography angiography and its various correlations

Purpose The aim of this study was to measure the foveal avascular zone (FAZ) area at both superficial and deep retinal capillary plexus levels in normal emmetropic and highly myopic eyes, using the Heidelberg optical coherence tomography angiography (OCTA) and to find its correlation with central macular thickness and volume and best-corrected visual acuity.Patients and methods This is a prospective cross-sectional observational study that involved 69 normal emmetropic and highly myopic eyes of Egyptian patients. FAZ area (both at the superficial and deep capillary plexus levels), central macular thickness, and volume were measured by the Heidelberg OCTA. Best-corrected visual acuity in Illiterate E lines was also reported.Results In normal individuals, the mean value of the FAZ was 0.38±0.11 mm2 for the superficial FAZ and 0.29±0.10 mm2 for the deep FAZ, with higher statistically significant values for the superficial FAZ size (P<0.05, t test=13.64). Pearson correlation test revealed a statistically significant negative correlation (P<0.05) between central macular thickness and both the superficial FAZ size (r=−0.33) and deep FAZ size (r=−0.39) and a highly significant negative correlation (P<0.01) between central macular volume and both superficial FAZ size (r=−0.40) and deep FAZ size (r=−0.42). Best-corrected visual acuity showed an insignificant correlation (P>0.05) with both superficial and deep FAZ size. Neither high myopia nor sex influenced the results.Conclusion Using the Heidelberg OCTA in normal Egyptian individuals, the superficial FAZ size ranged from 0.19 to 0.85 mm2, which was larger than the deep FAZ, which ranged from 0.09 to 0.73 mm2. FAZ size measurements were strongly correlated with central macular thickness and volume. Neither high myopia nor sex influenced the results.

Repeatability of Manual Measurement of Foveal Avascular Zone Area in Optical Coherence Tomography Angiography Images in High Myopia

PurposeTo analyze the repeatability of manual measurement of foveal avascular zone (FAZ) area in an optical coherence tomography angiography (OCTA) image in high myopia.MethodsThis study comprised patients with high myopia and controls. Two consecutive FAZ areas of the superficial and deep capillary plexus were obtained using OCTA. The intraclass correlation coefficient (ICC) and coefficient of variation (CV) were assessed, and univariate and multivariate generalized linear mixed models were conducted to identify factors related to repeatability.ResultsThirty eyes with high myopia and 34 eyes of healthy subjects were included in the study. The mean age in high myopia and control subjects was 55.5 and 60.8 years, respectively, the mean spherical equivalent was −9.98 and −0.55 diopters, and the mean axial length was 28.0 and 23.9 mm. The ICCs of FAZ area of the superficial capillary plexus (SCP) were 0.891 and 0.919, while the CVs were 8.8% and 8.5%. In measurement of the deep capillary plexus, the ICCs were 0.788 and 0.907, while the CVs were 11.2% and 11.0%, which were acceptable but exhibited lower repeatability than those of SCP. Multivariate analyses showed that older age (p = 0.030) and greater axial length (p = 0.005) were significantly associated with lower repeatability of SCP FAZ area measurements. In addition, greater axial length (p = 0.044) was a significant factor for lower repeatability of deep capillary plexus FAZ area measurements.ConclusionsManual measurement of FAZ area using OCTA exhibited relatively good repeatability for high myopia. Age and axial length affected repeatability and should be considered when analyzing FAZ areas in high myopia patients.

Foveal avascular zone area measurements using OCT angiography in patients with type 2 diabetes mellitus associated with essential hypertension

Objective. This study followed the variability in the foveal avascular zone (FAZ) area measured using optical coherence tomography angiography (OCTA) in patients with type 2 diabetes mellitus and high blood pressure. Material and Methods. This prospective, non-randomized, cohort study evaluated 46 eyes in 26 patients with high blood pressure associated with diabetic non-proliferative retinopathy (mild, medium, and severe forms) and diabetic proliferative retinopathy. Results. Our results showed early macular alterations (microaneurysms, leakage, neovascularizations, intraretinal microvascular abnormalities), a higher class of severity despite a relatively normal clinical aspect and higher values of FAZ associated with neovascularization undetected by SD-OCT (spectral domain-OCT). Conclusion. Measurement of the foveal avascular zone area using OCTA early detects macular alterations that precede classical retinography and SD-OCT determinations. Abbreviations: FAZ = foveal avascular zone; OCTA = optical coherence tomography angiography; IRMA = intraretinal microvascular abnormalities; SD-OCT = spectral domain-optical coherence tomography; OU = both eyes; PD = papillary diameter; ETDRS = early treatment diabetic retinopathy study; BP = blood pressure; OD = right eye.

CAPILLARY NETWORK ALTERATIONS IN X-LINKED RETINOSCHISIS IMAGED ON OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY.

To assess foveal and parafoveal vasculature at the superficial capillary plexus, deep capillary plexus, and choriocapillaris of patients with X-linked retinoschisis by means of optical coherence tomography angiography. Six patients with X-linked retinoschisis (12 eyes) and seven healthy controls (14 eyes) were recruited and underwent complete ophthalmologic examination, including best-corrected visual acuity, dilated fundoscopy, and 3 × 3-mm optical coherence tomography angiography macular scans (DRI OCT Triton; Topcon Corp). After segmentation and quality review, optical coherence tomography angiography slabs were imported into ImageJ 1.50 (NIH; Bethesda) and digitally binarized. Quantification of vessel density was performed after foveal avascular zone area measurement and exclusion. Patients were additionally divided into "responders" and "nonresponders" to dorzolamide therapy. Foveal avascular zone area resulted markedly enlarged at the deep capillary plexus (P < 0.001), particularly in nonresponders. Moreover, patients disclosed a significant deep capillary plexus rarefaction, when compared with controls (P: 0.04); however, a subanalysis revealed that this damage was limited to the fovea (P: 0.006). Finally, the enlargement of foveal avascular zone area positively correlated with a decline in best-corrected visual acuity (P: 0.01). Prominent foveal vascular impairment is detectable in the deep capillary plexus of patients with X-linked retinoschisis. Our results correlate with functional outcomes, suggesting a possible vascular role in X-linked retinoschisis clinical manifestations.

COMPARING FUNDUS FLUORESCEIN ANGIOGRAPHY AND SWEPT-SOURCE OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY IN THE EVALUATION OF DIABETIC MACULAR PERFUSION.

To compare fundus fluorescein angiography (FFA) and swept-source optical coherence tomography angiography (SS-OCTA) in the evaluation of macular perfusion in diabetic patients. Forty-one eyes (21 diabetic patients) seen at Moorfields Eye Hospital (London) over a 1-month interval underwent color fundus photography, FFA, and SS-OCTA imaging of the capillary superficial plexus using 2 different protocols: 3 × 3 mm and 4.5 × 4.5 mm. Quantitative assessment (foveal avascular zone diameters and area), qualitative analysis (macroscopic and microscopic levels) and Early Treatment Diabetic Retinopathy Study diabetic macular ischemia grading were performed. Artifacts were recorded. Intraclass correlation coefficients and weighted kappa values were calculated. Mean (SD) foveal avascular zone area was 0.695 (0.52) mm on FFA, 0.627 (0.54) mm on SS-OCTA 3 × 3 and 0.701 (0.54) mm on SS-OCTA 4.5 × 4.5 protocol. Intraclass correlation coefficients showed good agreement between FFA and SS-OCTA for both vertical diameter and foveal avascular zone area measurements. The agreement between SS-OCTA 3 × 3 and 4.5 × 4.5 was good for all quantitative measurements. Weighted kappa for diabetic macular ischemia grading showed low to fair agreement between FFA and SS-OCTA, whereas the agreement was good between two different SS-OCTA protocols. Swept-source OCTA is a reproducible technique in the assessment of macular perfusion in diabetic patients with special regards to foveal avascular zone analysis. The agreement with FFA is limited especially for diabetic macular ischemia grading. Fundus fluorescein angiography is more sensitive in identifying microaneurysms.

ACUTE EFFECT OF CAFFEINE ON MACULAR MICROCIRCULATION IN HEALTHY SUBJECTS: An Optical Coherence Tomography Angiography Study.

To evaluate the acute effects of caffeine on macular microvasculature using quantitative optical coherence tomography angiography analysis. Fifty-two healthy subjects aged 24 to 48 years were randomly divided into 2 groups: a control group, which received placebo, and a study group, which was subjected to caffeine. All participants underwent optical coherence tomography angiography at baseline and 1 hour after 200-mg oral caffeine intake in the study group and after oral placebo in the control group. Macular flow area, macular vessel density, and foveal avascular zone (FAZ) area were analyzed in both the groups. The study group consisted of 14 men and 12 women with a mean age of 40.6 ± 8.9 years. The mean age of control group was 39.5 ± 9.4 years, which consisted of 13 men and 13 women. Baseline macular flow area, vessel density, and FAZ area measurements of the study and control groups showed no significant difference (P > 0.05). Oral caffeine intake caused a significant reduction in macular flow area (superficial, deep, and choriocapillaris) and vessel density (P < 0.05). However, there was no statistically significant difference in FAZ area after caffeine intake when compared with baseline measurements (P = 0.063). We found a significant decrease in macular flow area (superficial, deep, and choriocapillaris) and vessel density after caffeine intake. Our findings are consistent with previous studies using other techniques. We believe that the results of this preliminary study will be useful in future studies about this topic.

Improved analysis of foveal avascular zone area with optical coherence tomography angiography.

To investigate the relationship between the foveal avascular zone (FAZ) and the inner nuclear layer (INL)-free zone in the center of the fovea in order to provide an improved approach to evaluation of the FAZ area with optical coherence tomography angiography (OCTA). Thirty-six healthy individuals (36 eyes) and 15 age-matched patients (15 eyes) with nonproliferative diabetic retinopathy (nPDR) were included in this study. The FAZ, as well as INL-free zone, was measured on OCTA images. The FAZ area, INL-free zone area, and the ratio of the INL-free zone area to the FAZ area were compared between healthy subjects and nPDR patients. The mean FAZ area in healthy subjects and nPDR patients was 0.33 ± 0.1mm2 and 0.41 ± 0.19mm2 (p < 0.05), respectively. The mean INL-free zone area in healthy subjects and nPDR patients was 0.33 ± 0.07mm2 and 0.25 ± 0.09mm2 (p > 0.05), respectively. The INL-free zone area to the FAZ area ratio in healthy subjects and nPDR patients was 1.08 ± 0.25 and 0.56 ± 0.18 (p < 0.001), respectively. Receiver operating characteristic analysis showed that the INL-free zone area to the FAZ area ratio had a higher area under curve (0.94; 80.0% sensitivity and 97.2% specificity) compared to the FAZ area (0.61; 40.0% sensitivity and 94.4% specificity) for differentiating nPDR from healthy eyes. This study showed that analysis of the FAZ based on the ratio of the INL-free zone area to the FAZ area has better accuracy compared to the conventional FAZ area measurement in differentiating eyes with mild to moderate nPDR without any structural abnormalities in the fovea from healthy eyes.

Repeatability and Reproducibility of Foveal Avascular Zone Area Measurement on Normal Eyes by Different Optical Coherence Tomography Angiography Instruments

Purpose: To compare the foveal avascular zone (FAZ) area measurements produced by different optical coherence tomography angiography (OCTA). Methods: Healthy enrolled volunteers underwent OCTA using 2 different devices: Spectralis HRA+OCTA (Heidelberg Engineering, Heidelberg, Germany) and RS-3000 Advance (Nidek, Gamagori, Japan). Two graders measured FAZ in both superficial (SCP) and deep (DCP) retinal capillary plexuses. The SCP and DCP en face images were visualized automatically segmenting 2 separate slabs defined by the arbitrary segmentation lines created by the software of each OCT device. One grader repeated each measure twice. Results: Fifty-nine eyes were included. The mean FAZ was 0.33 ± 0.09 mm² at the SCP and 0.57 ± 0.17 mm² at the DCP measured with RS-3000 versus 0.30 ± 0.08 and 0.35 ± 0.08 mm², respectively, measured with Spectralis. The measurements of the 2 devices were significantly different (p < 0.0001). The intraoperator agreement was excellent at the SCP (intraclass correlation coefficient, ICC: 0.97 with Spectralis and 0.96 with RS-3000). At the DCP, it was good with Spectralis and fair with RS-3000 (ICC: 0.85 and 0.64, respectively). The interoperator agreement was excellent for Spectralis and good for RS-3000 at the SCP (ICC: 0.97 and 0.93, respectively). It was good at the DCP with both devices (ICC: 0.74 with RS-3000 and 0.81 with Spectralis). Conclusions: FAZ measurements obtained with different OCTA devices differ. These findings should be considered in follow-up studies of patients with retinal vascular diseases.

Personalized analysis of foveal avascular zone with optical coherence tomography angiography

Aim. To investigate the relationship between the foveal avascular zone (FAZ) and inner nuclear layer (INL) free zone in order to provide a personalized approach for evaluation of the FAZ area with optical coherence tomography-angiography (OCTA).&#x0D; Material and methods.Thirty-six healthy individuals (36 eyes) and 9 patients (12 eyes) with nonproliferative diabetic retinopathy (nPDR) were included in this study. The FAZ area as well as INL-free zone were measured in superficial capillary plexus on OCTA images. The FAZ area, INL-free area, and the ratio of the INL-free area to the FAZ area were compared between healthy subjects and nPDR patients.&#x0D; Results. The mean FAZ area in healthy subjects and nPDR patients was 0.33 0.1 and 0.56 0.28 mm2 (p 0.05), respectively. The mean INL-free zone in healthy subjects and nPDR patients was 0.33 0.07 and 0.28 0.1 mm2 (p 0.05), respectively. The ratio of the INL-free area to the FAZ area in healthy subjects and nPDR patients was 1.08 0.25 and 0.57 0.2 (p 0.001), respectively. Receiver operating characteristic analysis showed that the ratio of the INL-free area to the FAZ area had the higher area under curve (0.98; 91.7% sensitivity and 97.2% specificity) compared to the FAZ area (0.8; 66.7% sensitivity and 87.1% specificity) for differentiating nPDR from healthy eyes.&#x0D; Conclusion. This study showed that personalized analysis of the FAZ area based on the relationship between the actual FAZ and INL-free zone has better diagnostic accuracy compared to the conventional FAZ area measurement on OCTA images.

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

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. 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). 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<0.001 with OCTA. CCC was 0.834 (95%CI: 0.746-0.893) P<0.001 and 0.890 (95%CI: 0.828-0.930) P<0.001 for parafoveal superficial and deep vessel density measurements, respectively. 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.

Axial Length Variation Impacts on Superficial Retinal Vessel Density and Foveal Avascular Zone Area Measurements Using Optical Coherence Tomography Angiography.

To evaluate the impact of image magnification correction on superficial retinal vessel density (SRVD) and foveal avascular zone area (FAZA) measurements using optical coherence tomography angiography (OCTA). Participants with healthy retinas were recruited for ocular biometry, refraction, and RTVue XR Avanti OCTA imaging with the 3 × 3-mm protocol. The foveal and parafoveal SRVD and FAZA were quantified with custom software before and after correction for magnification error using the Littman and the modified Bennett formulae. Relative changes between corrected and uncorrected SRVD and FAZA were calculated. Forty subjects were enrolled and the median (range) age of the participants was 30 (18-74) years. The mean (range) spherical equivalent refractive error was -1.65 (-8.00 to +4.88) diopters and mean (range) axial length was 24.42 mm (21.27-28.85). Images from 13 eyes were excluded due to poor image quality leaving 67 for analysis. Relative changes in foveal and parafoveal SRVD and FAZA after correction ranged from -20% to +10%, -3% to +2%, and -20% to +51%, respectively. Image size correction in measurements of foveal SRVD and FAZA was greater than 5% in 51% and 74% of eyes, respectively. In contrast, 100% of eyes had less than 5% correction in measurements of parafoveal SRVD. Ocular biometry should be performed with OCTA to correct image magnification error induced by axial length variation. We advise caution when interpreting interocular and interindividual comparisons of SRVD and FAZA derived from OCTA without image size correction.

Visualization of changes in the foveal avascular zone in both observed and treated diabetic macular edema using optical coherence tomography angiography

BackgroundCentral vision loss in diabetic retinopathy is commonly related to diabetic macular edema (DME). The objective of this study was to describe changes between consecutive visits on optical coherence tomography angiography (OCTA) of the foveal avascular zone (FAZ) in eyes with DME.Methods20 eyes from 14 patients with DME were imaged on 2 successive clinic visits separated by at least 1 month. The mean interval between visits was 3.2 months. The only intervention used was intravitreal anti-VEGF in 11 eyes; the others were observed over time without treatment. Two different readers measured FAZ area using a pseudo-automated tool in comparison to a manual tracing tool. Qualitative changes in the appearance of the vasculature surrounding the FAZ were also recorded. The retinal capillary plexus was segmented into deep and superficial plexuses, and FAZ measurements were done on the superficial, deep, and summated plexuses.ResultsPseudo-automated and manual measurements of FAZ area decreased significantly (p < 0.05) between visits in the deep, superficial, and summated plexuses. Qualitative analysis of vasculature surrounding the FAZ showed that most of the vascular changes (65%) over time were visible in the deep plexus, compared to 30 and 20% in the superficial and summated plexuses, respectively.ConclusionsThe most significant differences in FAZ size over time were in the summated plexus (p < 0.001), while changes in FAZ appearance were most prominent in the deep plexus. Absolute decrease in FAZ size over visits was largest in the deep plexus. Our results demonstrate that OCTA can effectively be used to measure FAZ area in patients with DME, visualize qualitative changes in retinal vasculature, and visualize the segmentation levels at which these changes can be best appreciated. However, larger studies are needed to evaluate the reproducibility of manual and pseudo-automated measuring techniques.

Repeatability and Reproducibility of Foveal Avascular Zone Area Measurements Using AngioPlex Spectral Domain Optical Coherence Tomography Angiography in Healthy Subjects

Purpose: The aim of this study was to evaluate the repeatability and reproducibility of foveal avascular zone (FAZ) area measurements using AngioPlex spectral domain optical coherence tomography (OCT) angiography in normal subjects. Methods: Twenty-two healthy subjects (25 eyes) underwent FAZ area measurements with AngioPlex OCT. Each volunteer was separately examined 3 consecutive times by the 2 experienced observers. The FAZ area was measured using ImageJ software. Intraobserver repeatability was evaluated by calculating the coefficient of variation (CoV) and intraclass correlation coefficient (ICC). Interobserver reproducibility was also assessed using the Bland-Altman test and concordance correlation coefficient (CCC). Results: The FAZ areas were measured as 0.373 ± 0.109 and 0.377 ± 0.112 mm² by observers 1 and 2, respectively. The repeatability assessment of the FAZ area measurements yielded CoV values of 0.029 and 0.034 and ICC values of 0.997 and 0.996 by observers 1 and 2, respectively. The mean difference between the 2 observers was 0.004. CCC values ranged from 0.9705 to 0.9844. Conclusions: The FAZ area measurements obtained using AngioPlex OCT showed a good repeatability and reproducibility in healthy subjects. Excellent reliability makes AngioPlex OCT a valid device for measuring the FAZ area.