Foveal Avascular Zone Measurements Research Articles

Investigation of Retinal Alterations in Patients Recovered from COVID-19: A Comparative Study

ABSTRACT Aim : To evaluate any abnormalities on retinal examination and retinal microvascularity in patients recovered from COVID-19. Materials and Methods : Cross-sectional, case- control study. Patients between 18 and 65 years old with PCR-confirmed SARS-CoV-2 infection and age matched controls were included. Macular and retinal nerve fiber layer thickness, vessel density of the superficial (SCP) and the deep retinal capillary plexus (DCP) and the foveal avascular zone (FAZ) were measured and compared with controls. Results : This study included 200 eyes of 200 cases totally. Of them 105 cases were patients and 95 cases were controls. Retinal abnormalities were detected by indirect ophthalmoscopic examination in ten patients of 105 cases (10.5%). There was no statistically significant difference in the vessel density of the SCP and the DCP and the mean FAZ measurements. Conclusion : There isn’t any relevant difference between early post-COVID-19 patients and general population in terms of retinal microvascularity.

Retinal Vessel Parameters and Choroidal Thickness using Optical Coherence Tomography and OCT Angiogram in Normal Children: A Cross-sectional Study

Introduction: Optical Coherence Tomography (OCT) and OCT Angiogram (OCT-A) are non invasive techniques for imaging the microvasculature of retina and choroid. OCT is a method of analysing the in-vivo retinal architecture. OCT uses low coherence interferometry to create a cross-sectional map of the retina with a resolution of 10-15 µm. Swept Source OCT utilises light source of 1050 nm wavelength and can reproducibly measure choroidal thickness. OCT-A uses the principle of motion contrast, where the moving red blood cells are traced to depict vessels through different segments of the retina. The same tissue area is imaged repeatedly and differences are analysed between scans to detect area with high flow rates, low flow and no flow at all. Only a few studies have been reported on baseline choroidal thickness and retinal vessel parameters in children. This study was conducted to measure these parameters using Swept source OCT in normal children. Aim: To measure retinal vasculature parameters and choroidal thickness using OCT and OCT-A in normal children. Materials and Methods: A cross-sectional study was conducted on 68 children between 5-15 years of age in Department of Ophthalmology, Christian Medical College and Hospital, Vellore, Tamil Nadu, India between February 2018 to July 2018, after obtaining the Ethical clearance from the Institutional review board. The children were divided into two groups, 5-10 years and >10-15 years. Children with Best Corrected Visual Acuity (BCVA) <6/6, axial length< 20/ >25 mm, any systemic disease or ocular pathology were excluded. All underwent comprehensive ophthalmic examination along with fundus photography, OCT and OCTA imaging. Retinal artery and vein calibre at the disc margin and Subfoveal Choroidal Thickness (SFCT) were measured. Measurement of Foveal Avascular Zone (FAZ) both superficial and deep, vascular density (VD) of perifoveal, papillary and peripapillary area were obtained from OCT-A. T-test was used to compare the parameters with p value <0.05 considered as significant. Results: A total of 136 eyes were included. Mean retinal artery measured at superior and inferior disc margin was 176.84±43.88 µm and 177.78±41.69 µm respectively. Mean retinal vein measured at superior and inferior disc margin was 218.90±46.36 µm and 235.37±48.07 µm respectively. Perifoveal images were clear and vessel densities could be anlaysed but papillary and peripapillary vessel densities were not analysed due to poor image quality in many subjects. The mean retinal artery caliber in the age group 5-10 years was 179.85±45.62 µm and 174.00±42.30 µm in the age group >10-15 years at the superior disc margin with p-value of (0.4403). There was no statistical difference retinal vessel caliber between the two groups. The mean SFCT in the 5-10 years group was 344.42±86.77 µm and 343.40± 93.56 µm in the other with a p value 0.9474. The mean superficial FAZ (SFAZ) was189.79±117.11 µm2 in the first group and 264.88±169.91 µm2 in the second group,( p=0.0034). There was no statistical difference among these parameters between the two groups except SFAZ, p=0.0034. Conclusion: Present study describes the normative data on retinal vasculature parameters and choroidal thickness in Indian paediatric population aged 5 to 15 years using OCT and OCT-A. The study findings will further help in screening and monitoring the subjects in this age group.

The Impact of Axial Eye Growth on Foveal Avascular Zone Measurements in Children.

SIGNIFICANCEFoveal avascular zone (FAZ) area is a frequently used biomarker in diseases impacting the retinal vasculature in pediatric populations. Variation in axial length between individuals results in differences in lateral image scale, which affect the accuracy of FAZ area measurements. Accordingly, changes in axial length over time within individual children would affect estimates of FAZ area change.PURPOSEThis study aimed to quantify how changes in axial length over time affect estimates of FAZ area change using optical coherence tomography angiography (OCT-A) images.METHODSTwenty pediatric participants (<18 years old) and 40 adult participants were imaged on Optovue's Avanti system (Fremont, CA) and had axial length measurements acquired at two time points. The FAZ was segmented twice using the OCT-A image at each time point. Foveal avascular zone area was estimated at both time points using the assumed/fixed axial length of the OCT-A device (unscaled) and using the participant's axial length (scaled). Changes in FAZ area over time were compared between the pediatric and adult groups using both unscaled and scaled data.RESULTSThe average ± standard deviation follow-up time was 3.35 ± 1.66 years for the pediatric group and 2.90 ± 1.65 years for the adult group. Using unscaled data, FAZ area seemed to decrease between visits in the pediatric group (P = .004), whereas the FAZ area increased between visits in the adult group (P = .003). When correctly scaled data were used, the FAZ area still increased between visits for the adult group (P < .001), although the FAZ area no longer showed a significant change between visits for the pediatric group (P = .37). When comparing the normalized FAZ area change across visits between unscaled and scaled data, a significant difference was found between the adult and pediatric groups (P < .001).CONCLUSIONSScaled data should be used when measuring FAZ area in pediatric populations, especially in longitudinal studies.

Stability of OCT and OCTA in the Intensive Therapy Unit Setting.

To assess the stability of retinal structure and blood flow measures over time and in different clinical settings using portable optical coherence tomography angiography (OCTA) as a potential biomarker of central perfusion in critical illness, 18 oesophagectomy patients completed retinal structure and blood flow measurements by portable OCT and OCTA in the eye clinic and intensive therapy unit (ITU) across three timepoints: (1) pre-operation in a clinic setting; (2) 24–48 h post-operation during ITU admission; and (3) seven days post-operation, if the patient was still admitted. Blood flow and macular structural measures were stable between the examination settings, with no consistent variation between pre- and post-operation scans, while retinal nerve fibre layer thickness increased in the post-operative scans (+2.31 µm, p = 0.001). Foveal avascular zone (FAZ) measurements were the most stable, with an intraclass correlation coefficient of up to 0.92 for right eye FAZ area. Blood flow and structural measures were lower in left eyes than right eyes. Retinal blood flow assessed in patients before and during an ITU stay using portable OCTA showed no systematic differences between the clinical settings. The stability of retinal blood flow measures suggests the potential for portable OCTA to provide clinically useful measures in ITU patients.

Spatial positional relationship between macular superficial vessel density and ganglion cell-inner plexiform layer thickness in primary angle closure glaucoma

PurposeTo evaluate the spatial relationship between macular superficial vessel density (SVD) and macular ganglion cell-inner plexiform layer (GCIPL) thickness in primary angle closure glaucoma (PACG), and to investigate diagnostic abilities of macular SVD and foveal avascular zone (FAZ) parameters.MethodsThis was a cross-sectional study on 38 PACG patients (38 eyes) and 25 healthy subjects (25 eyes). Macular region was imaged using a 1050-nm-wavelength swept-source optical coherence tomography (OCT) angiography (OCTA) system (DRI OCT Triton, TOPCON). Vessel density of the macular region was quantified by ImageJ software. The peripapillary retinal nerve fiber layer (pRNFL) thicknesses and macular GCIPL thickness were obtained by swept-source OCT. Pearson correlation analysis was used to evaluate the spatial positional relationship between macular SVD and macular GCIPL thickness. At the same time, the correlation between macular SVD and pRNFL thickness was evaluated. Areas under the receiver operating characteristics curves (AUCs) of OCT, OCTA and FAZ measurement metrics were calculated to assess the diagnostic ability for glaucoma.ResultsMacular GCIPL thickness had a moderate correlation with the macular SVD in the inferonasal sector (r = 0.426, P = 0.008). In addition, there was a strong correlation between inferonasal sector of macular vessel density and 5,6,7,8 clock-hour regions of the pRNFL thicknesses (all r > 0.5). Inferoinferior sector of macular SVD and 6,7 clock-hour regions of pRNFL thicknesses also had strong correlation (all r > 0.5). The AUCs of macular SVD ranged between 0.61 (superonasal sector) and 0.76 (inferoinferior sector). The FAZ circularity index showed the highest diagnostic power (AUC = 0.94;95% CI, 0.85–0.99), followed by superotemporal sector of macular GCIPL thicknesses (0.93;95% CI,0.83–0.98).ConclusionsSector of macular SVD not only had a spatial positional correlation with corresponding macular GCIPL thickness, but also with clock-hour regional pRNFL thicknesses in PACG eyes. FAZ circulation index might be a useful diagnostic parameter.

Evaluation of migraine patients with optical coherence tomography angiography.

To compare optical coherence tomography angiography (OCTA) findings in cases with migraine and healthy controls. Thirty-eight eyes of 19 patients with migraine with aura and 38 eyes of 19 healthy subjects were enrolled in this prospective and comparative study. All patients and healthy controls were evaluated with OCTA (Triton, Topcon®, Tokyo, Japan). Central macular thickness (CMT), optic disc parameters (such as retinal nerve fibre layer [RNFL] thickness and rim and disc areas), foveal avascular zone (FAZ) and parafoveal superficial vessel density (VD) measurements were analysed. The optic disc rim area was significantly larger in the migraine group compared to the control group (p = 0.009). In OCTA measurements, the FAZ area was significantly larger in migraine patients (p = 0.001). The parafoveal superficial VD measurements were found to be lower in the migraine patients in all quadrants, but not statistically significant. Weak negative correlations were found between superior parafoveal VD and disease duration in migraine patients. Migraine with aura was associated with optic disc rim changes, but without any remarkable foveal vascular decrements. It is possible for migraine to cause structural changes due to its chronic nature.

Diabetic Macular Ischemia Diagnosis: Comparison between Optical Coherence Tomography Angiography &amp; Fundus Fluorescein Angiography

Background: OCT-A is developing as a new non-invasive rapid technique which may replace FFA as a gold standard procedure for diagnosis of DMI. Aim of the Work: Comparison between fluorescein angiography (FA) and optical coherence tomography angiography (OCTA) for imaging of foveal avascular zone (FAZ) in diabetic retinopathy patients (DR) affected and not affected by diabetic macular ischemia, (DMI). Subjects and Methods: In this prospective study, 30 eyes for 30 patients and separated by macular status as 19 eyes with DMI and 11 eyes without DMI instructed to undergo OCT-A scan, FFA. Full ophthalmological examination was done and patients signed their informed consents. Results: Of the 30 patients, 13 females and 17 males with a mean age of 52.63 ± 11.9 years. 17 eyes with DMI and 13 eyes without DMI have underwent full ophthalmological examination, BCVA measurement, FFA and OCT-A. BCVA was higher among eyes without DMI (0.5 ±0.2) as compared with eyes with DMI (0.25 ±0.2). Mean time for FFA was 9.4 ± 3.2 m and for OCT-A was 1.5 ± 0.8 m. OCTA can save time than FFA by 85%. 57% was affected with artifacts with OCT-A while 7% has allergic reactions to flourescien dye. Subjects with DMI presented a mean area on FA and OCTA of 0.85 ± 0.2 mm2 and 0.79± 0.2 mm2, respectively (p = 0.001). Patients without DMI presented a mean area on FA and OCTA of 0.39 ± 0.1 mm2 and 0.36 ± 0.1 mm2, respectively (p = 0.01). The ICC for the FAZ measurements between the 2 observers on FA and OCTA was 0.98 and 0.99, respectively. Conclusion: OCTA represents a novel technique to diagnose DMI and it may become an alternative to FA for this purpose.

Repeatability of Optical Coherence Tomography Angiography Measurements in Patients with Retinal Vein Occlusion.

PurposeTo analyze the repeatability of vessel density (VD) measurements and manual foveal avascular zone (FAZ) measurements using optical coherence tomography angiography (OCTA) in patients with retinal vein occlusion (RVO) without macular edema.MethodsThe study population consisted of patients with RVO and central macular thickness <300 μm. For each subject, measurements were performed twice with a 5-minute interval. The intraclass correlation coefficient (ICC) and coefficient of variation (CV) were calculated to analyze the repeatability of results obtained with the OCTA device. To identify factors related to repeatability, we performed Pearson correlation analyses based on the CV of potential factors.ResultsA total of 48 eyes were included in the study. The ICCs of the VDs in superficial capillary plexus (SCP) and the deep capillary plexus (DCP) were 0.748 and 0.665, respectively, and the CVs of the VDs in SCP and DCP were 9.1% and 12.6%, respectively. The ICCs associated with the FAZ of the superficial layer (SFAZ) and that of the deep layer (DFAZ) were 0.965 and 0.956, respectively, and the CV of the SFAZ and DFAZ were 8.8% and 9.7%, respectively. From Pearson correlation analyses, OCTA quality was significantly correlated with the CV of the VDs of SCP and DCP. However, there were no variables that were significantly correlated with the CV of SFAZ and DFAZ, including OCTA quality.ConclusionsVD measurements in the SCP layer using OCTA exhibited good repeatability, and VD measurements in the DCP layer exhibited relatively low repeatability compared to that of SCP layer measurements in patients with RVO without macular edema after treatment with bevacizumab. Manual measurement of the FAZ area in both SCP and DCP layers resulted in good repeatability. In addition, the repeatability of VD measurements in SCP and DCP layers was correlated with OCTA image quality.

Reduction of Foveal Avascular Zone After Vitrectomy Demonstrated by Optical Coherence Tomography Angiography.

Purpose: To investigate the effect of pars plana vitrectomy on foveal circulation, and in particular the foveal avascular zone (FAZ), using optical coherence tomography angiography (OCTA).Methods: This was a prospective, non-randomized, comparative case series of patients that underwent vitrectomy. Twenty-six eyes of 26 patients that underwent vitrectomy were studied postoperatively by OCTA. Our patients underwent 23 or 25G pars plana vitrectomy (PPV) for any posterior segment pathology. Three-dimensional OCTAs (DRI Triton Swept Source OCT; Topcon) of the capillary plexus were obtained three months post-operatively. The FAZ measurements of the fellow eyes were used as controls.Main outcome measures: Change in FAZ area between vitrectomized eyes and controls.Results: From a total of 26 patients, 17 underwent vitrectomy due to retinal detachment (RD). Almost all patients demonstrated a statistically significant reduction in FAZ size based on the OCTA measurements. Τhe mean difference in FAZ size for the superficial capillary plexus (SCP) was -93.77 ± 71.73 μm and for the deep capillary plexus (DCP) -88.87 ± 75.41 μm, both statistically significant (p=0.000), while the amount of reduction in μm was the same for both SCP and DCP.Conclusion: The foveal avascular zone seems to be reduced following vitrectomy as shown by optical coherence tomography angiography. It is postulated that this may be the result of changes in the physiology of the vitrectomized eye, and that this change should be attributed to the removal of the vitreous itself rather than other structures such as the internal limiting membrane.

Evaluation of retinal vessel density and foveal avascular zone measurements in patients with obstructive sleep apnea syndrome.

To compare retinal capillary plexus vessel densities, choroidal thickness, optic disc vessel densities and foveal avascular zone measurements between normal subjects and subjects with obstructive sleep apnea syndrome (OSAS) using spectral-domain OCT angiography (OCTA). Forty eyes of patients with overall OSAS, 20 eyes of patients with mild-moderate OSAS, 20 eyes of patients with severe OSAS on polysomnography and 21 controls were evaluated with the RTVue-XR Avanti OCTA (Optovue, Inc., Fremont, CA). Superficial and deep retinal capillary plexus vessel densities, choroidal thickness and foveal avascular zone (FAZ) parameters (area, diameter, acircularity index of the FAZ, foveal density-300) were measured for all subjects. Superficial capillary plexus vessel densities of the groups were similar. Deep capillary plexus (DCP) vessel densities of all three OSAS groups decreased in the parafoveal region (< 0.001). In the perifoveal region, DCP vessel densities were decreased in the Overall OSAS group (p = 0.023) and in the Severe OSAS group (p = 0.021), whereas it was similar in the Mild-moderate OSAS group. Choroidal thickness decreased in all three OSAS groups (p < 0.001). All FAZ measurements and foveal density-300 measurements were similar compared to the control group. Our findings indicate that in severe OSAS patients, deep parafoveal, perifoveal vascular densities decrease and the choroid layer becomes thinner. When evaluating a patient with OSAS, it should be kept in mind that there may be eye involvement due to the disease.

Comparison between two multimodal imaging platforms: Nidek Mirante and Heidelberg Spectralis.

To investigate the reliability and comparability of retinal measurements obtained with spectral-domain optical coherence tomography (OCT), optical coherence tomography angiography (OCTA), confocal scanning laser ophthalmoscopy (cSLO) colour images, and fundus autofluorescence (FAF) between two multimodal imaging platforms in eyes with macular pathology and normal, healthy volunteers. This cross-sectional, multi-centre, instrument validation study recruited 94 consecutive subjects. All participants underwent a dilated examination and were scanned consecutively on the Heidelberg Spectralis (Heidelberg Engineering, Heidelberg, Germany) and Nidek Mirante (Nidek Co. Ltd., Gamagori, Japan) devices. Agreement between device images were evaluated from measures of the central retinal thickness (CRT), presence of segmentation and fixation imaging artefacts (IA), foveal avascular zone (FAZ) measurements; as well as sensitivity and specificity values from the detection of atrophy on fundus autofluorescence (FAF), drusen, subretinal drusenoid deposits, geographic atrophy, epiretinal membrane, fibrosis and haemorrhage on multicolour imaging, and agreement between devices and groups. Compared with reference clinical examination, sensitivity values for the identification of retinal features using sole device images ranged from 100% for epiretinal membranes to 66.7% for subretinal drusenoid deposits (SSD). Mean absolute difference for CRT between OCT devices was 3.78μm (95% confidence interval [CI]: - 21.39 to 28.95, P = 0.809). Differences in the superficial and deep capillary plexus FAZ area on OCTA between devices were not statistically significant (P = 0.881 and P = 0.595, respectively). IAs were significantly increased in the presence of macular pathology. Comparison of retinal measurements between the OCT devices did not differ significantly. Common ultrastructural biomarkers of multiple macular pathologies were identified with high sensitivities and specificities, with good agreement between graders, indicating that they can be identified with comparable confidence in retinal imaging between the two devices.

Evaluation of Peripapillary and Macular Vascular Flow Changes with OCT-A in Patients with Superficial Optic Disk Drusen.

ObjectivesThe purpose of this study was to compare the peripapillary and macular vascular flow changes between healthy adults and adult patients with superficial optic disk drusen (ODD), as evaluated by optical coherence tomography angiography (OCT-A).MethodsIn this retrospective study, 44 eyes of 22 patients with superficial ODD followed-up in our neuro-ophthalmology unit and 54 eyes of 27 healthy individuals admitted to our clinic for routine ophthalmological examination were included in the study. The superior, inferior, nasal, and temporal radial peripapillary capillary plexus (RPC) vessel density (VD) values; superior, inferior, nasal, and temporal parafoveal and foveal region superficial capillary plexus (SCP) and deep capillary plexus (DCP) VD values; and choriocapillaris flow (CCF) area and foveal avascular zone area were evaluated by OCT-A.ResultsThere was no statistically significant difference between groups in terms of age and sex. While there was a significant decrease in the temporal RPC VD values in cases with ODD (p=0.02), no significant difference was observed in other quadrants. No significant differences in either parafoveal zone four quadrant, foveal SCP and DCP VD values, or foveal avascular zone measurements were found between groups, while CCF area values were significantly higher in the study group (p=0.012).ConclusionCompared to healthy controls, our results showed a decrease in the RPC temporal quadrant VD values, and an increase in CCF area in cases with superficial ODD. To evaluate the effects of ODD on optic nerve head and macular perfusion, and to understand its underlying mechanisms and secondary complications, longer follow-up studies with larger case series are needed.

Autoimmune retinopathy: findings and limitations from optical coherence tomography angiography

Background and objectiveTo report novel findings and limitations from optical coherence tomography angiography (OCTA) in the evaluation of autoimmune retinopathy (AIR).Study designWe retrospectively reviewed features of five patients diagnosed with AIR and five controls. OCTA scans were obtained and manually segmented to provide accurate measurements of foveal avascular zone (FAZ), vessel density, and retinal thickness at different levels.ResultsThe total retina and superficial vessel density throughout the whole scan were similar between AIR and controls (p = 0.14 and p = 0.11), whereas deep vessel density was decreased in AIR compared controls (p = 0.02). Decreased vessel density was most pronounced in the parafoveal and perifoveal areas (p = 0.01 and p = 0.01). AIR patients also had reduction of total retinal thickness in the perifoveal zone (p = 0.03), corresponding to outer retinal thinning (p = 0.001).ConclusionThis small series shows that AIR patients have reduced deep vessel density, particularly in the parafoveal and perifoveal regions and a decrease in macular thickness. These findings show correlation with the classic “flying saucer” sign seen on OCT.

A quantitative comparison of four optical coherence tomography angiography devices in healthy eyes.

Optical coherence tomography angiography (OCT-A) is a novel imaging modality for the diagnosis of chorioretinal diseases. A number of FDA-approved OCT-A devices are currently commercially available, each with unique algorithms and scanning protocols. Although several published studies have compared different combinations of OCT-A machines, there is a lack of agreement on the consistency of measurements across OCT-A devices. Therefore, we conducted a prospective quantitative comparison of four available OCT-A platforms. Subjects were scanned on four devices: Optovue RTVue-XR, Heidelberg Spectralis OCT2 module, Zeiss Plex Elite 9000 Swept-Source OCT, and Topcon DRI-OCT Triton Swept-Source OCT. 3 mm × 3 mm images were utilized for analysis. Foveal avascular zone (FAZ) area was separately and independently measured by two investigators. Fractal dimension (FD), superficial capillary plexus (SCP), and deep capillary plexus (DCP) vessel densities (VD) were calculated from binarized images using the Fiji image processing software. SCP and DCP VD were further calculated after images were skeletonized. Repeated measures ANOVA, post hoc tests, and interclass correlation coefficient (ICC) were performed for statistical analysis. Sixteen healthy eyes from sixteen patients were scanned on the four devices. Images of five eyes from the Triton device were excluded due to poor image quality; thus, the authors performed two sets comparisons, one with and one without the Triton machine. FAZ area showed no significant difference across devices with an ICC of > 95%. However, there were statistically significant differences for SCP and DCP VD both before and after skeletonization (p < 0.05). Fractal analysis revealed no significant difference of FD at the SCP; however, a statistically significant difference was found for FD at the DCP layer (p < 0.05). The results showed that FAZ measurements were consistent across all four devices, while significant differences in VD and FD measurements existed. Therefore, we suggest that for both clinical follow-up and research studies, FAZ area is a useful parameter for OCT-A image analysis when measurements are made on different machines, while VD and FD show significant variability when measured across devices.

Reliability of foveal avascular zone measurements in eyes with retinal vein occlusion using optical coherence tomography angiography

BackgroundTo evaluate the reliability of foveal avascular zone (FAZ) area measurements using optical coherence tomography angiography (OCTA) in eyes with retinal vein occlusion (RVO).MethodsTwenty-five OCTA exams of patients with RVO were evaluated retrospectively. Three examiners performed manual measurements of the FAZ, and interrater and intrarater reliability were obtained.ResultsThe intraclass correlation coefficient (ICC) for interrater reliability for individual measurements was 0.62 (moderate) with a 95% confidence interval (CI) of 0.40 to 0.79 (p < 0.001). The ICC (95% CI) for intrarater reliability was 0.92 (0.82 to 0.96) for rater A, 0.96 (0.91 to 0.98) for B, and 0.88 (0.76 to 0.94) for C (p < 0.001). In all subanalyses including presence of edema and type of occlusion, interrater reliability was poor/moderate, and intrarater reliability was good/excellent.ConclusionThe FAZ varies significantly among eyes with RVO, so measurements obtained using OCTA should be analyzed with caution due to the moderate level of reliability among different examiners.

Different effect of media opacity on automated and manual measurement of foveal avascular zone of optical coherence tomography angiographies

BackgroundOptical coherence tomography angiography (OCTA) provides not only visualisation but also quantitative measurement of foveal avascular zone (FAZ). Media opacity is common in elderly subjects with cataracts. This study aimed...

Ethnic differences in normal retinal capillary density and foveal avascular zone measurements.

The purpose of this study was to quantify retinal capillary density and foveal avascular zone (FAZ) area in healthy subjects according to their ethnicity, using optical coherence tomography angiography (OCTA). In this cross-sectional study, all eyes underwent swept-source OCTA (Triton, Topcon, Tokyo, Japan). Macular OCTA scans (3 × 3mm) were obtained in healthy white Caucasian and black African subjects. The FAZ area and capillary density in both the superficial (SCP) and deep capillary plexuses (DCP) were automatically measured using a custom-made software combining vessel binarization and skeletonization. Twelve eyes of 12 healthy Caucasians and 15 eyes of 15 healthy black Africans were included in the analysis. The mean FAZ area was significantly smaller, and the overall vessel density (VD) was higher in the SCP and DCP of Caucasians compared to black Africans. The mean FAZ area was 0.26 ± 0.008mm2 in the SCP and 0.25 ± 0.05mm2 in the DCP in Caucasians versus 0.33 ± 0.08mm2 in the SCP (p = 0.01) and 0.37 ± 0.1mm2 in the DCP (p = 0.03) in Africans. In the SCP and DCP, the mean VD was, respectively, 40.5 ± 0.8% and 47.1 ± 0.5% in Caucasians versus 34.3 ± 1% (p = 0.008) and 40.6 ± 0.9% in Africans (p < 0.001). In the SCP and DCP, VD is lower in black Africans compared to Caucasians. In OCTA studies on vascular diseases, ethnicity-matched measurements from healthy subjects should be used for comparisons.

Evaluation of choroidal thickness and retinal vessel density in patients with inactive Graves' orbitopathy.

To investigate choroidal thickness using spectral domain-optical coherence tomography and retinal vessel density with optical coherence tomography angiography in patients with inactive Graves' orbitopathy. A total of 36 eyes of 36 patients with inactive Graves' orbitopathy (6 men and 30 women in Group 1) and 36 eyes from 36 controls (8 men and 28 women in Group 2) were recruited for this prospective case-control study. Choroidal thickness measurements were obtained using enhanced depth imaging with spectral domain-optical coherence tomography. Optical coherence tomography angiography images were generated with 6 × 6-mm angiographic optical coherence tomography scans. Retinal vessel densities of the superficial retinal layer and deep retinal layer of the macula and foveal avascular zone measurements were obtained for each eye. The mean age was 42.5 ± 9.9 years in Group 1 and 42.8 ± 6.5 years in Group 2 (p = 0.76). The mean choroidal thickness was 370.7 ± 83.5 μm and 338.2 ± 72.4 μm in Group 1 and 2, respectively (p = 0.09). There was no significant difference between the groups in retinal vessel density either in superficial or deep retinal layers (p > 0.05 for all), and no difference was found between the groups in foveal avascular zone area and perimeter (p = 0.69, p = 0.73, respectively). Similar retinal vessel density values were found in both superficial and deep retinal layers in Graves' orbitopathy compared with healthy subjects. Although statistically insignificant, choroidal thickness was slightly higher in patients with Graves' orbitopathy than in healthy subjects. Foveal avascular zone area and perimeter measurements were unaffected by the disease.

Multimodal imaging of aberrant macular microvessel crossing the foveal avascular zone in two young adults

BackgroundThe traditional view is that there are no vessels in the foveal avascular zone. The two cases we report show microvessels crossing the foveal avascular zone.Case presentationA man and a woman, both 25 years old, were both incidentally found on optical coherence tomography angiography (OCTA) to have unilateral aberrant microvessels crossing the foveal avascular zone in their left eyes. Visual acuity was preserved in both patients. The vessel density (VD) and perfusion density (PD) of the eyes with the aberrant microvessels were all higher than those of the contralateral eyes. Nevertheless, measurements of foveal avascular zone (FAZ) dimensions, including its area, perimeter and circularity, were smaller in the left eyes than in the right eyes. No complications were recorded.ConclusionsTo date, aberrant microvessels crossing the foveal avascular zone have not been found to impair visual function. OCTA is a non-invasive and quick method that does not require dilation or the use of fluorescein dye. It is a reliable tool for the detection of aberrant microvessels crossing the foveal avascular zone.

Evaluation of microvascular network with optical coherence tomography angiography (OCTA) in branch retinal vein occlusion (BRVO)

BackgroundTo evaluate changes of microvascular network of macular and peripapillary regions and to provide a quantitative measurement of foveal avascular zone (FAZ) in unilateral BRVO patients.MethodsForty-seven unilateral BRVO patients and forty-seven normal controls were enrolled. A 3*3 mm scan centered on fovea followed by a 4.5*4.5 mm scan centered on optic nerve head (ONH) were obtained in BRVO eyes, fellow eyes and control eyes of each individual using OCTA (Optovue Inc., Fremont, CA, USA). Vessel density (VD) in superficial (SVC) and deep vascular complex (DVC) of macula and radial peripapillary capillary (RPC) were automatically calculated. Parameters of FAZ region including size, perimeter, acircularity index (AI) and foveal vessel density 300 (FD-300) were measured.ResultsVDs of SCV and DVC were significantly lower, especially in affected regions, in BRVO eyes compared with fellow eyes (P < 0.05). BRVO affected eyes has larger FAZ size, FAZ perimeter, AI and lower FD-300 compared with fellow eyes (all P < 0.05). VD of SVC and FD-300 were lower in fellow eyes compared with normal control eyes (P < 0.05). The average vessel density in whole area and peripapillary area in BRVO eyes were significantly lower compared with fellow eyes (P < 0.05). VD of inside disc in fellow eyes was lower than normal eyes (P < 0.05).ConclusionsOCTA provided quantitative information of vascular changes in BRVO. FAZ in BRVO eyes showed significant morphological alterations and decreases of VD in surrounding area. Decreases of VD existed not only in SVC and DVC in macular region but also in RPCs in BRVO eyes. Unaffected eyes of unilateral BRVO showed vascular abnormalities in superficial retinal layer, peri-FAZ area and also peripapillary regions.