Foveal Avascular Zone Diameter Research Articles

Investigation of OCTA Biomarkers in Fabry Disease: A Long Term Follow-Up of Macular Vessel Area Density and Foveal Avascular Zone Metrics.

Retinal microvasculature is known to be altered in patients with Fabry disease (FD). We aimed to investigate the long-term changes in macular microvasculature and explore a reliable retinal biomarker for treatment monitoring in FD. Prospective study of 26 eyes with FD followed up to 48months (mean 24, range 8-48). OCT angiography (OCTA) images (2.9 × 2.9mm) were obtained using Heidelberg Spectralis II at baseline and follow-up. Macular vessel area density (VAD, %) was measured in three layers: superficial vascular plexus (SVP), intermediate capillary plexus (ICP) and deep capillary plexus (DCP) in three peri-macular circular sectors (c1, c2, c3). Additionally, foveal avascular zone (FAZ) area (mm2) and horizontal and vertical diameters (µm) were assessed. VAD decreased over time in SVP, ICP (in sectors c2 and c3) and DCP (all sectors) (p < 0.04). VAD reduction was predominantly seen in treated FD patients. FAZ and horizontal diameters increased at follow-up in FD patients compared to baseline (p ≤ 0.025). Correlation analysis showed a moderate to strong negative correlation between VAD of SVP and DCP in the innermost circle and FAZ in treated patients (r = - 0.6; p < 0.0001). This is the first long-term follow-up OCTA study in FD to our knowledge. A decrease in VAD, pronounced in the peripheral circle and deeper layers, as well as an enlargement of the FAZ could be observed over time. These changes reflect the vascular remodelling during the course of the disease. Interestingly, the reduction of VAD was more pronounced in treated patients. This could be a result of enzyme replacement therapy and could be potentially used as a reliable biomarker for monitoring the treatment of the disease. A baseline examination of VAD and FAZ before treatment initiation is meaningful. Larger studies are needed to establish the use of VAD and FAZ as biomarkers for treatment monitoring.

Foveal Avascular Zone in diabetic hypertensive patients

Purpose To evaluate changes that occur in foveal avascular zone (FAZ) in diabetic hypertensive patients by optical coherence tomography angiography (OCTA). Patients and methods OCTA was performed for 60 eyes of 35 diabetic hypertensive patients. This study was done in Benha University Hospital between February and June 2021. FAZ area was measured by a frame that was centered around it. Moreover, the vessel density was measured also by detecting the superficial vessel density (SVD) and the deep vessel density (DVD). Results In diabetic hypertensive (60 eyes of 35 patients) with average age 55.52 (±6.88) years and mean duration of the disease 12.17 (±7.15) years, the mean value of the FAZ was 0.37 (±0.54) mm, denoting enlargement of the FAZ diameter. In addition, the vessel density showed that there is decreasing in the SVD (43.9±5.89) and it was correlated to the best-corrected visual acuity and age of the patients (P&lt;0.05), while it was highly correlated to the DVD (P&lt;0.001). On the other hand, there was a decrease in DVD with a mean of 43.17±7.44, which was statistically significant with the age of the patients (P&lt;0.05), but there was no significant relationship with duration of the disease, glycated hemoglobin, and best-corrected visual acuity. Conclusion OCTA is a noninvasive technique to image the retinal and choroidal vasculature. The study concluded that diabetic retinopathy in the presence of systemic hypertension leads to increasing of the FAZ area. Moreover, it leads to decreasing in both the SVD and DVD. Also, it allows for early detection and easy follow-up of the disease.

Quantitative OCT Angiography Assessment of the Effect of Peribulbar Anesthesia on Retinal Microvasculature in Primary Open-Angle Glaucoma Patients Undergoing Cataract Surgery.

ObjectiveTo assess the effect of peribulbar anesthesia on retinal microvasculature in primary open-angle glaucoma (POAG) patients undergoing cataract surgery using OCT Angiography.ParticipantsForty-nine patients undergoing cataract surgery were divided into two groups. Group I included patients with no history of glaucoma, while group II included patients previously diagnosed as POAG with controlled IOP. Each participant received 6 mL of peribulbar anesthetic injection of 4 mL lidocaine 2% containing 150 IU hyaluronidase and 2 mL bupivacaine 0.5%. They were scanned with the OCT-A 10 minutes before and 10 minutes after injection for foveal deep (DCP), superficial (SCP) capillary plexuses density and total vessel density, foveal avascular zone (FAZ) diameter, optic disc total vessel density, and radial peripapillary capillary (RPC) network density. In addition, IOP was checked before and 10 minutes after injection.ResultsMedian percent change in DCP post-injection was significantly greater in group II (−43%) than in group I (−2.5%) (P < 0.001). Also, DCP total density median percent change post-injection was significantly higher in group II (−21%) than in group I (−0.9%) (P < 0.001). Foveal SCP vessel density and total vessel density median percent change post-injection were −62.6% and −16.2%, respectively, in group II and were −2.6% and −1.1%, respectively, in group I, which are statistically significant (P < 0.001). The FAZ diameter median percentage change post-injection was higher in group II (40.6%) than in group I (2.5%) (P < 0.001). Optic disc total vessel density and radial peripapillary capillary (RPC) network density post-injection median percent change were significantly higher in group II (−13.6%) and (−13.1%) respectively than in group I (−1.1%) and (−1.25%) respectively (P < 0.001).ConclusionPeribulbar anesthesia harbors a deleterious ischemic effect on the retinal vascular tree of glaucoma patients, which could harmfully affect the vision and the visual field in those vulnerable patients.

Morphological Characteristics of Normal Foveal Avascular Zone by Optical Coherence Tomography Angiography.

Purpose To provide quantitative measurements for the foveal avascular zone (FAZ) and to describe its morphological characteristics by optical coherence tomography angiography (OCT-A). Design Cross-sectional observational case series. Methods Healthy volunteers were recruited and evaluated using Triton-DRI SS-OCT Angiography. A 4.5 × 4.5 mm square was evaluated by OCT-A center around the fovea. Superficial and deep capillary plexus were identified, and different quantitative measurements were conducted along with categorization of the FAZ pattern. Results Eighty-two eyes (41 volunteers) were evaluated. Mean age was 30.59 ± 7.6 years (23–42 years). Mean subcentral retinal thickness was 200.1 ± 5.66 um (192–210 um). The number of terminal vessels was variable (range, 8–11). Mean maximum terminal vessel-to-vessel intervening distance was 527.8 ± 60.3 um (471–674 um). Mean minimum terminal vessel-to-vessel intervening distance was 296.7 ± 45.8 um (233–373 um). Mean maximum horizontal diameter of FAZ (superficial) was 716.17 ± 124.09 um, while mean maximum vertical diameter of FAZ (superficial) was 667.76 ± 131.28 um. Mean maximum horizontal diameter of FAZ (deep) was 823.19 ± 144.92 um, while mean maximum vertical diameter of FAZ (deep) was 794.03 ± 150.28 um. OCT-A detected different FAZ patterns; horizontally oval configuration in 32 eyes (39%), rounded configuration in 24 eyes (29.3%), pentagon configuration in 14 eyes (17.1%), and vertically oval and nonspecific configuration in 6 eyes each (7.3%). Conclusion OCT-A could efficiently provide both quantitative and qualitative assessment of normal FAZ; such characterizations were difficult by standard FAZ assessment procedures like FFA.

Evaluation of retinal neurovascular structures by optical coherence tomography and optical coherence tomography angiography in children and adolescents with type 1 diabetes mellitus without clinical sign of diabetic retinopathy.

The aim of the study was to investigate whether retinal neurovascular structural impairment in children and adolescents with type 1 diabetes mellitus (T1D) without clinical signs of diabetic retinopathy (DR) could be detected early via optical coherence tomography (OCT) and OCT angiography (OCTA). In the current prospective, cross-sectional, observational clinical study children and adolescents with T1D without DR were evaluated between December 2018 and May 2019. Retinal neurovascular structures in the macular and optic disc regions were examined in detail and quantitatively assessed using OCT and OCTA. Data from subjects with T1D were compared with data from healthy controls. Whether retinal neurovascular structural changes were significantly associated with puberty stage, diabetes duration, and HbA1c level was also investigated. The T1D group included 110 eyes and the control group included 84 eyes. In the T1D group the mean inside disc vessel density (VD) was significantly lower than that of the control group (p < 0.001), as was the mean superior temporal disc VD (p < 0.043). Puberty stage was significantly associated with retinal thickness, parafoveal superficial capillary plexus VD, and peripapillary retinal nerve fiber layer thickness (p < 0.05). Diabetes duration and HbA1c level was significantly correlated with retinal layer thickness, foveal avascular zone diameter, and superficial and deep capillary plexus VDs. In children and adolescents with T1D without clinical signs of DR, the VD of the disc region is affected earlier than the macular region. In these patients, early neurovascular impairment can be detected non-invasively via OCT and OCTA.

Effect of Prematurity on Foveal Development in Early School-Age Children

To evaluate the foveal development in preterm children with optical coherence tomography and OCT angiography. Retrospective cohort study. This study included children aged 6-8 years who were born prematurely and who did not receive retinopathy treatment. They were evaluated between September 2018 and July 2019, categorized according to gestational age (GA) (group I: GA ≤30weeks; group II: GA between 31 and 34weeks), and compared with full-term children (group III). Central foveal thickness (CFT), inner retinal thickness (IRT), outer retinal thickness (ORT), subfoveal choroidal thickness (CT), temporal and nasal CT, foveal avascular zone (FAZ) diameter, and vessel densities of superficial (SCP-VD) and deep capillary plexuses (DCP-VD) of the foveal and parafoveal areas were examined in detail. The study included 126 eyes of 63 patients (group I: 40 eyes; group II: 46 eyes; and group III: 40 eyes). In group I, CFT, IRT, ORT, foveal SCP-VD, and foveal DCP-VD were significantly greater than those in the other groups, and temporal CT and FAZ diameter were significantly lower (P < .05). GA showed a significant negative correlation with CFT, IRT, ORT, foveal SCP-VD, and foveal DCP-VD and a significant positive correlation with subfoveal CT, temporal and nasal CT, and FAZ diameter (P < .05). The morphological and vascular foveal structures in early school-age children who were born premature were different from those of full-term children. These differences were correlated with GA and more pronounced in those with GA of ≤30weeks.

THE RAP STUDY, REPORT TWO

To explore the regional distribution of macular neovascularization type 3 (MNV3). Seventy-eight eyes of 78 patients were reviewed. We defined the location of each lesion after applying a modified ETDRS grid and the incidence of simultaneous MNV1 or 2. Also, we investigated the distribution of MNV3 at the outline of the foveal avascular zone and when the diameter of foveal avascular zone was less than 325 µm. The distribution of MNV3 was 4 lesions (5%) from the center to 500 µm, 72 (92%) from 500 µm to 1500 µm, and 2 (3%) from 1,500 µm to 3000 µm. The distribution in respect of the ETDRS fields was 7 (9%) nasal, 16 (20%) superior, 32 (40%) temporal, and 23 (31%) inferior. No additional MNV1 or 2 were found elsewhere. Most lesions tended to distribute along straight bands radiating from the perifoveal area, mainly in the temporal half (72%). None of the cases had MNV3 at the boundary of the foveal avascular zone. Only five cases had foveal avascular zone diameter of less than 325 µm, the closest lesion was 425 µm away from the center. MNV3 lesions are most likely neither symmetrical nor uniformly distributed. They have a higher affinity to distribute radially in the temporal perifoveal area.

Foveal Avascular Zone Distortion in Epiretinal Membrane by Optical Coherence Tomography Angiography.

To show the morphologic changes on the foveal avascular zone (FAZ) in patients with epiretinal membrane (ERM) using optical coherence tomography angiography (OCTA) and to demonstrate the correlation between distortion of FAZ and features of the ERM. FAZ eccentricity index (longest diameter of FAZ/shortest diameter of FAZ) was measured in 52 patients with ERM and compared with 27 healthy subjects' values. The density of the ERM was quantified using a grading scale (0-3) on multicolor scanning laser images, and spectral-domain OCT characteristics of the eyes were assessed. Of the 52 eyes with ERM, 31 eyes (59.61%) showed some foveal remodeling, including full (13.46%) or partial (30.76%) apparent vascularization of FAZ, presence of a vessel crossing the fovea (9.61%), and horizontal or vertical elongation of FAZ (5.76%). The mean FAZ eccentricity index was 0.84 ± 0.46 (range: 0.0-1.86) in eyes with ERM and 0.98 ± 0.07 (range: 0.96-1.02) in the control subjects, respectively (P = .02). There was a negative significant correlation between FAZ eccentricity index and central macular thickness (P = .04). Thickening of the central fovea leads to foveal remodeling in ERM eyes, and OCTA enables the visualization of architectural FAZ changes. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:295-301.].

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.

Relationship between the morphology of the foveal avascular zone, retinal structure, and macular circulation in patients with diabetes mellitus

Diabetic Retinopathy (DR) is an extremely severe and common degenerative disease. The purpose of this study was to quantify the relationship between various parameters including the Foveal Avascular Zone (FAZ) morphology, retinal layer thickness, and retinal hemodynamic properties in healthy controls and patients with diabetes mellitus (DM) with and with no mild DR (MDR) using Spectral-Domain Optical Coherence Tomography (Spectralis SDOCT, Heidelberg Engineering GmbH, Germany) and the Retinal Function Imager (Optical Imaging, Ltd., Rehovot, Israel). Our results showed a higher FAZ area and diameter in MDR patients. Blood flow analysis also showed that there is a significantly smaller venous blood flow velocity in MDR patients. Also, a significant difference in roundness was observed between DM and MDR groups supporting the development of asymmetrical FAZ expansion with worsening DR. Our results suggest a potential anisotropy in the mechanical properties of the diabetic retina with no retinopathy that may trigger the FAZ elongation in a preferred direction resulting in either thinning or thickening of intraretinal layers in the inner and outer segments of the retina as a result of autoregulation. A detailed understanding of these relationships may facilitate earlier detection of DR, allowing for preservation of vision and better clinical outcomes.

Pathophysiological correlations between fundus fluorescein angiography and optical coherence tomography results in patients with idiopathic epiretinal membranes.

The aim of the current study was to determine the association between fundus fluorescein angiography (FFA) image results, optical coherence tomography (OCT) imaging results and visual functions in patients with idiopathic epiretinal membranes (ERMs). A total of 80 eyes from 40 patients diagnosed with ERM were analyzed. Best-corrected visual acuity (BCVA) and metamorphopsia were measured using the Early Treatment Diabetic Retinopathy Study eye chart and M-charts, respectively. Macular thickness and volume were determined using OCT. Macular vascular leakage and distortion, and foveal avascular zone (FAZ) diameters were assessed using FFA. BCVA and M-chart results confirmed macular degeneration in the affected eyes. The area of macular vascular leakage was positively correlated with macular volume (r=0.50; P=0.001). The ratio of FAZ diameters was negatively correlated with central macular thickness (r=−0.41; P=0.008). The grade of macular vascular distortion was positively correlated with macular thickness (all r≥0.47; P<0.01) and volume (r=0.53; P<0.001). The results of the current study demonstrated that FFA may effectively identify the degree of changes in retinal macular vasculature. Vascular distortion, measured by FFA, may reflect changes in macular structure and visual functions. These results suggest a potential application of FFA in the pre- and post-surgical evaluation of patients with ERMs.

Quantitative characteristics of sickle cell retinopathy in optical coherence tomography angiography

Early detection is an essential step for effective intervention of sickle cell retinopathy (SCR). Emerging optical coherence tomography angiography (OCTA) provides excellent three-dimensional (3D) resolution to enable label-free, noninvasive visualization of retinal vascular structures, promising improved sensitivity in detecting SCR. However, quantitative analysis of SCR characteristics in OCTA images is yet to be established. In this study, we conducted comprehensive analysis of six OCTA parameters, including blood vessel tortuosity, vessel diameter, vessel perimeter index (VPI), area of foveal avascular zone (FAZ), contour irregularity of FAZ and parafoveal avascular density. Compared to traditional retinal thickness analysis, five of these six OCTA parameters show improved sensitivity for SCR detection than retinal thickness. It is observed that the most sensitive parameters were the contour irregularity of FAZ in the superficial layer and avascular density in temporal regions, while the area of FAZ, tortuosity and mean diameter of the vessel were moderately sensitive.

Foveal Avascular Zone in Normal Tension Glaucoma Measured by Optical Coherence Tomography Angiography.

Aim To measure diameter of foveal avascular zone (FAZ), FAZ area, and vessel density using Optical Coherence Tomography Angiography (OCT-A) in patients with normal tension glaucoma (NTG) and to establish the possible role of OCT-A in diagnosis and follow-up of patients with NTG. Methods Twenty-one eyes of 21 patients with NTG and 30 eyes of 30 healthy subjects underwent complete ophthalmic examination as well as OCT-A on ZEISS AngioPlex. 3 × 3 macula scans were used to measure vertical, horizontal, and maximum diameter of FAZ by two graders. Mean values and interobserver variability were analyzed. Image J was used for analysis of FAZ area and vessel density. Results Mean vertical diameter (t = 5.58, p < 0.001), horizontal diameter (t = 3.59, p < 0.001), maximum diameter (t = 5.94, p < 0.001), and FAZ area (t = 5.76, p < 0.001) were statistically significantly enlarged in the NTG group compared to those in the control group. Vessel density (t = −5.80, p < 0.001) was statistically significantly decreased in the NTG group compared to that in the control group. Conclusion OCT-A could have an important role in the future in diagnosis of patients with NTG. In patients with NTG, there is larger FAZ area, while the vessel density is reduced in comparison to the control group.

Diametric measurement of foveal avascular zone in healthy young adults using optical coherence tomography angiography.

BackgroundThe objective of this study is to measure the diameter size of foveal avascular zone (FAZ) in both eyes of healthy young adults using optical coherence tomography (OCT) angiography.MethodsA cross sectional study to measure the foveal avascular zone in healthy young adults. Subjects underwent OCT angiography using Zeiss AngioPlex OCT angiography in both eyes.Results30 eyes of 15 healthy young adults were evaluated. The mean horizontal FAZ diameter of superficial vascular plexus was 661.166 ± 119.99 microns and mean vertical FAZ diameter was 660.033 ± 96.169 microns (P = 0.9442). The mean horizontal FAZ diameter of deep vascular plexus was 1011.2 ± 154.526 microns and the mean vertical FAZ diameter of deep vascular plexus was 818.033 ± 102.108 microns. There was no difference between the contralateral eyes of subjects in FAZ diameter of both superficial and deep capillary plexuses.ConclusionThe mean diametric size of FAZ in superficial capillary plexus is 660.599 ± 0.801 microns and deep capillary plexus is 914.616 ± 136.589 microns. There was no significant difference with the contralateral eyes.

Optical Coherence Tomography Angiography of the Foveal Avascular Zone in Retinal Vein Occlusion

Purpose: The aim of the study was to visualize and to quantify pathological foveal avascular zone (FAZ) alterations through optical coherence tomography angiography (OCT-A) in eyes with retinal vein occlusion (RVO) in comparison to the unaffected fellow eyes. Procedures: OCT-A was conducted with the Avanti® RTVue 100 XR system (Optovue Inc., Fremont, Calif., USA). The borders of the superficial vascular layer (SVL) were defined as 3 μm below the internal limiting membrane and 15 μm below the inner plexiform layer, and for the deep vascular layer (DVL) as 15 and 70 μm below the inner plexiform layer, respectively. The length of the horizontal, vertical and maximum FAZ was manually measured for the SVL and DVL in each eye. Additionally, the angle between the maximum FAZ diameter and the papillomacular plane was measured. Results: OCT-A depicted defects within the perifoveal vasculature in eyes with branch retinal vein occlusion (BRVO; n = 11) and central retinal vein occlusion (CRVO; n = 8). These resulted in an enlargement of the maximum FAZ diameter in eyes with RVO (n = 19) in comparison to the healthy fellow eyes (n = 19; 921 ± 213 vs. 724 ± 145 µm; p = 0.008). Furthermore, a significant correlation was found between best-corrected visual acuity (BCVA) and the maximum FAZ diameter in the DVL (Spearman's ρ = -0.423, p < 0.01). Lastly, in the eyes with RVO, the angle between the papillomacular plane and the maximum FAZ diameter was only in 21.05% (SVL) and 15.79% (DVL) of the cases at 0 ± 15 or 90 ± 15°, respectively. In healthy eyes, these angles (which putatively represent a regular FAZ configuration) were more prevalent (SVL 68.42 vs. 21.05%, p = 0.003; DVL 73.68 vs. 15.79%, p < 0.001). Conclusion: OCT-A shows morphological alterations of the FAZ in eyes with CRVO and BRVO. The correlation of the maximum FAZ diameter with BCVA suggests that these alterations are functionally relevant.

Optical coherence tomography angiography of the foveal avascular zone in diabetic retinopathy.

PurposeTo analyze foveal avascular zone (FAZ) dimensions and symmetry in patients with diabetic retinopathy (DR) compared to healthy controls using optical coherence tomography angiography (OCT angiography).MethodsOCT angiography was performed via an Avanti® RTVue 100 XR OCT system (Optovue, Inc., Fremont, CA, USA) in patients with diabetes mellitus (DM) and healthy adults. A frame centered on the fovea was used for FAZ measurements. The borders of the superficial vascular layer were defined as 3 μm below the internal limiting membrane (ILM) and 15 μm below the inner plexiform layer (IPL), and for the deep vascular layer as15 μm and 70 μm below the IPL, respectively. Angles of maximum FAZ diameter were measured in all eyes by two graders.ResultsIn healthy eyes (N = 25), the FAZ surrounding vascular arcades were intact, showing a vertical or horizontal oval symmetrical formation with a maximum diameter usually on the horizontal or vertical axis. Diabetic eyes (N = 29) presented with disintegrity of the vascular arcades, resulting in an enlarged FAZ. In the superficial layer, the mean horizontal FAZ diameter was significantly larger in the DR group (753 μm ±272 μm) than in the control group (573 μm ±177 μm, p = 0.029). The difference was even more pronounced in the deep layer, with a mean value of 659 μm ±194 μm in the control group and 1009 μm ±342 μm in the DR group (p = 0.001). Furthermore, in the superficial layer, the angle of the maximum FAZ diameter was 0° (±15°) or 90° (±15°) in 72.0 % of healthy eyes. In eyes with DR, the angle was 0° (±15°) or 90° (±15°) in only 6.9 % of cases, due to the irregular configuration of the FAZ.ConclusionsOCT angiography is capable of imaging retinal vasculature without dye injection. Our data suggest that it can detect disintegrity of the vascular arcades surrounding the FAZ, thus differentiating DM from healthy eyes. Vascular abnormalities were more pronounced in the deep vascular layer.

ASSOCIATION BETWEEN MACULAR PERFUSION AND PHOTORECEPTOR LAYER STATUS IN DIABETIC MACULAR EDEMA

To evaluate the relationship between the photoreceptor layer status (inner segment ellipsoid band and external limiting membrane) and the foveal avascular zone size, as a result of macular perfusion, in patients with diabetic macular edema. This observational case series study included 151 eyes of 118 patients with naive diabetic macular edema. The length of the disrupted photoreceptor layer was assessed by optical coherence tomography. The foveal avascular zone diameter was measured on fluorescein angiogram. No significant association was found between the foveal avascular zone size and the mean lengths of the disrupted inner segment ellipsoid band nor the external limiting membrane in patients with naive diabetic macular edema. Macular ischemia, which lengthens the distance from the perifoveal vessels to the center of the fovea and may disrupt the normal flow of nutrients by simple diffusion to the photoreceptor line, does not seem to influence on inner segment ellipsoid band nor external limiting membrane integrity. Future studies may evaluate the effect of choroidal vascularization on the photoreceptor layer status to enhance the knowledge about the photoreceptor layer nutrients source.

The Association Between the Foveal Avascular Zone and Retinal Thickness

To investigate the association between the size and shape of the foveal avascular zone and retinal thickness in healthy subjects. In vivo imaging of the foveal microvasculature was performed on 32 subjects by using an adaptive optics scanning laser ophthalmoscope (AOSLO). Motion contrast maps of the AOSLO images were used to generate a montage revealing the foveal capillary network. Foveal avascular zone (FAZ) diameters along the horizontal (FAZH) and vertical (FAZV) meridians were measured on the montages. An asymmetry index (AI) of the FAZ was then computed as the ratio of the FAZH to FAZV. Retinal thickness was investigated by using spectral-domain optical coherence tomography (SDOCT). Inner retinal layer (INLFAZ) thickness and outer nuclear layer (ONLFAZ) thickness were measured at the edges of the FAZ on the horizontal and vertical SDOCT scans on the same eye. The foveal capillary network was readily visualized in all subjects. As expected there was individual variation in the size and shape of the FAZ. Along the horizontal and vertical meridians, the mean±SD (μm) of the FAZ diameter was 607±217 and 574±155, respectively. The INLFAZ thickness was 68±9 and 66±9, and the ONLFAZ thickness was 103±13 and 105±11, respectively. The mean±SD of the AI was 1.03±0.27. The difference between FAZH and FAZV decreases with increasing FAZ area (P=0.004). Mean ONLFAZ was negatively correlated with FAZ effective diameter (P<0.0001). No significant correlation was found between mean INLFAZ and FAZ effective diameter (P=0.16). Despite large individual variations in size and shape of the FAZ, the INLFAZ has a relatively constant thickness at the margins of the FAZ, suggesting the presence of retinal capillaries is needed to sustain an INLFAZ thickness greater than 60 μm. A smaller FAZ area is associated with a vertically elongated FAZ.

Foveal avascular zone and foveal pit formation after preterm birth

BackgroundVascularisation of the macula takes place between 24 and 27 weeks post-conception. Preterm birth may affect the formation of the foveal avascular zone (FAZ) and foveal depression, and displacement of...

Relationship between the Foveal Avascular Zone and Foveal Pit Morphology

To assess the relationship between foveal pit morphology and size of the foveal avascular zone (FAZ). Forty-two subjects were recruited. Volumetric images of the macula were obtained using spectral domain optical coherence tomography. Images of the FAZ were obtained using either a modified fundus camera or an adaptive optics scanning light ophthalmoscope. Foveal pit metrics (depth, diameter, slope, volume, and area) were automatically extracted from retinal thickness data, whereas the FAZ was manually segmented by two observers to extract estimates of FAZ diameter and area. Consistent with previous reports, the authors observed significant variation in foveal pit morphology. The average foveal pit volume was 0.081 mm(3) (range, 0.022 to 0.190 mm(3)). The size of the FAZ was also highly variable between persons, with FAZ area ranging from 0.05 to 1.05 mm(2) and FAZ diameter ranging from 0.20 to 1.08 mm. FAZ area was significantly correlated with foveal pit area, depth, and volume; deeper and broader foveal pits were associated with larger FAZs. Although these results are consistent with predictions from existing models of foveal development, more work is needed to confirm the developmental link between the size of the FAZ and the degree of foveal pit excavation. In addition, more work is needed to understand the relationship between these and other anatomic features of the human foveal region, including peak cone density, rod-free zone diameter, and Henle fiber layer.