Foveal Avascular Zone Morphology Research Articles

Optical Coherence Tomography Angiography Morphology following Rhegmatogenous Retinal Detachment Repair: ALIGN Post-Hoc Analysis.

To compare foveal avascular zone (FAZ) geometric indices using optical coherence tomography angiography (OCTA) in pneumatic retinopexy (PnR) vs pars plana vitrectomy (PPV) for rhegmatogenous retinal detachment (RRD). FAZ morphology was assessed as a possible imaging feature of retinal displacement. ALING post-hoc analysis included primary fovea-off RRDs that underwent successful PnR or PPV and OCTA and FAF at 3 months postoperatively, at St. Michael's Hospital, Toronto, Canada. FAZ area(mm2), axial ratio, circularity, and roundness were measured and FAF images were assessed for displacement. 72 patients were included, 78%(56/72) male, mean age of 60±9 years and 60%(43/72) phakic. 65%(47/72) and 35%(25/72) underwent PnR and PPV, respectively. Mean logMAR baseline visual acuity was 1.49±0.76. FAZ circularity was lower following PPV(0.629±0.120) versus PnR(0.703±0.122);p=0.016. 66 patients had gradable FAFs. Retinal displacement was present in 29%(19/66), 84.2%(16/19) of which had macular displacement. FAZ circularity was lower in eyes with macular displacement(0.613±0.110) versus those without displacement(0.700±0.124);p=0.015. There was a moderate negative correlation between 12-month aniseikonia and FAZ circularity(r=-0.262;p=0.041). FAZ circularity was lower following PPV and in eyes with macular displacement, and it was negatively correlated with 12-month aniseikonia scores. FAZ circularity may be another imaging feature to consider postoperatively following RRD repair.

An Open-source Image Analysis Toolbox for Quantitative Retinal Optical Coherence Tomography Angiography.

Qualitative and quantitative assessment of retinal perfusion using optical coherence tomography angiography (OCTA) has shown to be effective in the treatment and management of various retinal and optic nerve diseases. However, manual analyses of OCTA images to calculate metrics related to Foveal Avascular Zone (FAZ) morphology, and retinal vascular density and morphology are costly, time-consuming, subject to human error, and are exposed to both inter and intra operator variability. This study aimed to develop an open-source software framework for quantitative OCTA (QOCTA). Particularly, for analyzing OCTA images and measuring several indices describing microvascular morphology, vessel morphology, and FAZ morphology. In this analytical study, we developed a toolbox or QOCTA using image processing algorithms provided in MATLAB. The software automatically determines FAZ and measures several parameters related to both size and shape of FAZ including area, perimeter, Feret's diameter circularity, axial ratio, roundness, and solidity. The microvascular structure is derived from the processed image to estimate the vessel density (VD). To assess the reliability of the software, three independent operators measured the mentioned parameters for the eyes of 21 subjects. The consistency of the values was assessed using the intraclass correlation coefficient (ICC) index. Excellent consistency was observed between the measurements completed for the superficial layer, ICC >0.9. For the deep layer, good reliability in the measurements was achieved, ICC >0.7. The developed software is reliable; hence, it can facilitate quantitative OCTA, further statistical comparison in cohort OCTA studies, and can assist with obtaining deeper insights into retinal variations in various populations.

Subclinical retinal angiopathy associated with hereditary transthyretin amyloidosis – assessed with optical coherence tomography angiography

Background Retinal angiopathy is a known ocular manifestation of hereditary transthyretin amyloidosis (ATTRv). Optical coherence tomography angiography (OCT-A) is a recent noninvasive imaging technique, used in other retinal vascular diseases. Our purpose was to analyse subclinical changes in retinal vessels, with OCT-A, in patients with ATTRv amyloidosis. Methods Observational cross-sectional study in Centro Hospitalar e Universitário do Porto in the cohort of patients with genetic diagnosis of ATTRv. Patients were included if they had just one eye with scalloped iris (the other eye without scalloped iris), postulating eyes were at different stages, in the same patient. Patients were excluded if they had other manifestations of ocular ATTRv amyloidosis, namely clinical retinal angiopathy and/or vitreous opacities. The group of eyes with scalloped iris were compared with eyes without scalloped iris, using paired tests. Values are shown as Δ = mean difference between groups; p = p-value, d = Cohen’s d for effect size measurement. Results Twenty-four patients (24 eyes in each group) were included. Mean age was 46.5 ± 5.0 years. Eyes with scalloped iris showed attenuated retinal vascular network: larger foveal avascular zone (FAZ) area (Δ = +0.02 mm2, p = 0.002, d = 0.70); decreased foveal vascular density (Δ = –3.57%, p = 0.001, d = –0.75); superficial (Δ = –1.50%, p = 0.049, d = –0.43) and deep (Δ = –2.53%, p = 0.023, d = –0.50) plexus vascular density. Acircularity index was superior in scalloped iris eyes (Δ = 0.04, p = 0.004, d = –0.65), representing an abnormal FAZ morphology. Conclusion Scalloped iris in ATTRv eyes are associated with a more advanced subclinical retinal angiopathy, than eyes without scalloped iris. Our results identify for the first time and in vivo, early changes in retinal vessels in ATTRv amyloidosis. Henceforward, OCT-A may play a role in the evaluation of ATTRv patients oculopathy and the effectiveness of future eye targeting treatments.

Glaucomatous Macular Vasculature: A Quantitative Analysis

Background: The aim of this study was to evaluate the characteristics of the macular vessel density (VD) and the foveal avascular zone (FAZ) in glaucoma quantitatively using the optical coherence tomography angiography (OCT-A).
 Methods: Twenty-five eyes of 13 patients with primary open angle glaucoma (POAG) and 12 eyes of 6 healthy participants were enrolled retrospectively. Functional visual field (VF) and structural Spectral-Domain optical coherence tomography (SD-OCT) Retinal Nerve Fiber Layer Thickness (RNFLT) were assessed in all participants. OCT-A was performed on a fovea centered, 15x10 degrees, macular region. OCT-A scans were processed with MATLAB software and automatically graded to define FAZ parameters. The parafoveal VD in the superficial and deep retinal vascular plexus (SVP and DVP) was analyzed by quadrant and circular segmented zones.
 Results: Foveal Avascular Zone -Major Axis Length (p=0.02), Area (p=0.04), Equivalent Diameter (p=0.04) and Perimeter (p=0.04) were significantly larger in glaucoma than the control group. Regarding SVP and DVP, the average macular total VD were lower in glaucoma patients compared to the control group (p<0.01; p<0.01). Additionally, the inner circular region (p=0.04; p<0.01 respectively for SVP and DVP) and all quadrants except for North had a lower VD in glaucoma group compared to the control group. Assessment of the total VD successfully predicted RNFLT (p<0.001) and was significantly associated with the probability of glaucoma (p=0.009).
 Conclusion: OCT-A parameters, namely the FAZ morphology and the macular VD, were associated with glaucomatous functional and structural changes. The macular VD showed a considerable diagnostic value. It may be a modern biomarker, representing microvascular network disruption of the macular perfusion in glaucoma.

Retinal Vessel Density in Exudative and Nonexudative Age-Related Macular Degeneration on Optical Coherence Tomography Angiography

Although the choroid contributes to the pathogenesis of age-related macular degeneration (AMD), the role of retinal perfusion is unclear. We sought to compare retinal vascular measurements between eyes with nonexudative and exudative AMD using optical coherence tomography angiography (OCT-A). Retrospective, cross-sectional study. OCT-A images were analyzed from 310 eyes of 182 patients (mean age ± standard deviation [SD], 78.8 ± 8.8 years) with nonexudative (54.2%) and exudative (45.8%) AMD to measure retinal vessel density (VD) from the superficial capillary plexus in the foveal, parafoveal, and full macular regions and foveal avascular zone (FAZ) area, perimeter, and circularity. Multivariate regressions were used to compare nonexudative and exudative AMD eyes and the impact of anti-vascular endothelial growth factor (anti-VEGF) treatments or geographic atrophy (GA). In eyes with AMD, VD decreases with age in the foveal (β=-0.211, P < .001), parafoveal (β=-0.305, P < .001), and full macular regions (β=-0.295, P < .001). Eyes with exudative AMD demonstrated lower VD, especially in the parafoveal (29.8% ± 6.3% vs 33.0% ± 5.7%, P < .001) and full regions (27.9% ± 6.2% vs 31.2% ± 5.5%, P < .001) compared with nonexudative AMD. There were no differences in FAZ area, perimeter, or circularity between the 2 groups (P= .503-.907). In eyes with exudative AMD, previous anti-VEGF treatments did not impact retinal vascular measurements (P= .324-.986). Nonexudative AMD severity and presence of central GA also impacted retinal VD and FAZ morphology. Retinal VD is decreased in eyes with exudative AMD compared with nonexudative AMD but is unaffected by anti-VEGF treatments, suggesting a retinal vascular contribution to the pathogenesis of AMD.

Foveal avascular zone morphology and parafoveal capillary perfusion in sickle cell retinopathy

Background/aimsTo assess foveal avascular zone (FAZ) morphology and parafoveal capillary perfusion in patients with various stages of sickle cell retinopathy (SCR) using optical coherence tomography angiography (OCT-A).MethodsThis is a multi-institutional...

Within-subject assessment of foveal avascular zone enlargement in different stages of diabetic retinopathy using en face OCT reflectance and OCT angiography.

Enlargement of the foveal avascular zone (FAZ) due to progressive capillary nonperfusion is associated with visual deterioration in patients with diabetic retinopathy. The FAZ area has long been considered an important clinical marker of advancing retinopathy. However, a large body of literature shows that the FAZ area varies considerably in healthy eyes, resulting in substantial overlap between controls and diabetics, thus reducing its discriminatory value. In this study, within-subject FAZ area enlargement was obtained by the comparison of the structural FAZ area to the functional FAZ area using simultaneously-acquired, corresponding en face OCT reflectance and OCT angiography images. Our study suggests that en face OCT reflectance images provide useful anatomic baselines of structural FAZ morphology prior to the onset of disease. Measurements of within-subject FAZ area enlargement appear to be a more sensitive method for identifying the onset of diabetic retinopathy as compared to using OCT angiographic measurements of FAZ alone.

Variability of Foveal Avascular Zone Metrics Derived From Optical Coherence Tomography Angiography Images.

PurposeTo characterize sources of inter- and intrasubject variability in quantitative foveal avascular zone (FAZ) metrics.MethodsTwo 3×3-mm optical coherence tomography angiography scans (centered on the fovea) were acquired in both eyes of 175 subjects. An image of the superficial plexus was extracted from each scan and segmented twice by a single observer. Four quantitative FAZ morphology metrics (area, axis ratio, acircularity, major horizontal axis angle) were calculated, and a variance components analysis was performed.ResultsMean (±SD) age was 27.9 ± 11.9 years, and 55% were female. Area had the largest amount of variance resulting from intersubject differences (93.1%). In contrast, there was large interocular variance for axis ratio, acircularity, and major horizontal axis angle (55.0%, 53.7%, 70.7%, respectively), though only axis ratio showed significant asymmetry between fellow eyes (P < 0.05). Neither repeated images from the same eye nor repeated segmentation on the same image were significant sources of variance.ConclusionsMetrics of FAZ morphology show excellent repeatability and reliability. Excluding FAZ area, there was a high amount of variance attributed to interocular differences for the other FAZ metrics; therefore, the fellow eye should not be considered a control for FAZ studies when using these metrics.Translational RelevanceVision scientists must be prudent when choosing FAZ metrics, as they display varying degrees of within-subject differences relative to between-subject differences. It seems likely that different metrics will be best suited for different tasks, such as monitoring small changes over time within a single subject or assessing whether a given FAZ is abnormal.

Algorithm for predicting macular dysfunction based on moment invariants classification of the foveal avascular zone in functional retinal images

Abstract Introduction A new method for segmenting and quantifying the macular area based on morphological alternating sequential filtering (ASF) is proposed. Previous studies show that persons with diabetes present alterations in the foveal avascular zone (FAZ) prior to the appearance of retinopathy. Thus, a proper characterization of FAZ using a method of automatic classification and prediction is a supportive and complementary tool for medical evaluation of the macular region, and may be useful for possible early treatment of eye diseases in persons without diabetic retinopathy. Methods We obtained high-resolution retinal images using a non-invasive functional imaging system called Retinal Function Imager to generate a series of combined capillary perfusion maps. We filtered sequentially the macular images to reduce the complexity by ASF. Then we segmented the FAZ using watershed transform from an automatic selection of markers. Using Hu’s moment invariants as a descriptor, we can automatically classify and categorize each FAZ. Results The FAZ differences between non-diabetic volunteers and diabetic subjects were automatically distinguished by the proposed system with an accuracy of 81%. Conclusion This is an innovative method to classify FAZ using a fully automatic algorithm for segmentation (based on morphological operators) and for the classification (based on descriptor formed by Hu’s moments) despite the presence of edema or other structures. This is an alternative tool for eye exams, which may contribute to the analysis and evaluation of FAZ morphology, promoting the prevention of macular impairment in diabetics without retinopathy.

Evaluation of macular and peripapillary vessel flow density in eyes with no known pathology using optical coherence tomography angiography

PurposeTo assess normal vessel flow density (VFD) in macular and peripapillary regions of eyes with no known ocular pathology using optical coherence tomography angiography (OCTA).MethodsAngioVue (Optovue, Fremont, CA, USA) was used to capture OCTA images. A 3 × 3 mm grid and a 4.5 × 4.5 mm grid was used to scan parafoveal and peripapillary regions, respectively. ReVue software was utilized to measure VFD in five sectors within the inner two circles of ETDRS grid in macular region and correlated to retinal thickness of same sectors. At optic disc, VFD was calculated in six sectors based on Garway-Heath map. Area and morphology of foveal avascular zone (FAZ) was correlated with VFD in central 1 mm. The influence of myopia on mean VFD was also assessed.ResultsTwenty-four eyes (mean age: 30 years) were analyzed. Mean VFD in macular sectors was 43.5 (±4.5) and 45.8 (±5.0) % in superficial and deep retinal plexuses, respectively. Mean VFD was significantly higher in deep retinal plexus compared to superficial retinal plexus in all sectors except central 1 mm (p < 0.05). Mean VFD in central 1 mm increases with an increase in central retinal thickness in both superficial and deep retinal plexuses (p < 0.001). Mean parafoveal VFD at level of both superficial and deep retinal plexuses decrease with an increase in spherical equivalent in myopics (p < 0.05). Mean VFD in myopics was found to be significantly lower in parafoveal region of deep retinal plexus (p < 0.05). Mean area of FAZ was 0.33 (±0.15) and 0.47 mm2 (±0.15) in superficial and deep retinal plexuses, respectively. Area of FAZ decreases with an increase in central 1 mm thickness and foveal VFD (p < 0.001).ConclusionsOCTA may be used to measure VFD in macular and peripapillary regions. Vessels in the parafoveal region are more densely packed in the deep retinal plexus leading to higher VFD compared to superficial plexus. Thicker retina in fovea translates into higher foveal VFD due to more compact arrangement of retinal layers and continuity of inner nuclear layer (INL). Myopia is associated with lower VFD in parafoveal region at level of deep retinal plexuses which may explain thinning of INL in myopics.

Systematic Evaluation of Optical Coherence Tomography Angiography in Retinal Vein Occlusion

To evaluate the clinical utility of optical coherence tomography angiography (OCTA) in patients with retinal vein occlusion (RVO), and to systematically compare OCTA images with changes seen on color fundus photography and fluorescein angiography (FA). Reliability analysis. Eighty-one eyes of 76 patients with a history of RVO (branch, central, or hemicentral), both acute and chronic, underwent OCTA and color fundus photography. In 29 eyes, data were compared to FA imaging. Comparative and multimodal analysis of the 3 imaging procedures were performed. We identified good agreement between FA and OCTA scans centered on the macula for capillary nonperfusion (intraclass correlation coefficient [ICC] 0.825 for the 3 × 3-mm scan and 0.891 for the 8 × 8-mm scan). Agreement for area of capillary changes (dilation, pruning, and telangiectasia) was also substantial (ICC 0.712 for the 3 × 3-mm scan and 0.787 for the 8 × 8-mm scan). For foveal avascular zone grading, agreement was good for the 3 × 3-mm scan (kappa = 1.000 for radius and kappa = 0.799 for outline) but poor for the 8 × 8-mm scan (kappa = 0.156 for radius and kappa = 0.600 for outline). The quality of the images obtained was an important issue for OCTA, as 15.1% of scans were nongradable, particularly in patients unable to maintain fixation. OCTA is a quick, reliable, and noninvasive method to evaluate the area of capillary nonperfusion and foveal avascular zone morphology in patients with RVO. However, good fixation is a requirement for acquisition of good-quality images.