Measurement of Foveal Avascular Zone Dimensions and its Reliability in Healthy Eyes Using Optical Coherence Tomography Angiography

PURPOSE. To assess the relationship between the size of the foveal avascular zone (FAZ; area and perimeter) and vessel density (VD) at various retinal regions using optical coherence tomography angiography (OCTA) in patients with open-angle glaucoma (OAG).METHODS. In this retrospective cross-sectional study, OAG eyes were grouped according to the presence/absence of central visual field (CVF) defects. A control group of normal eyes was also included. OCTA images were obtained from the optic nerve (4.5 3 4.5 mm 2 ) and macular (3 3 3 mm 2 ) area, in which VDs were measured in the circumpapilla, parafovea, and fovea regions. Partial correlation analyses between FAZ parameters representing size and VDs at different retinal regions were performed. The correlation between FAZ parameters and macular ganglion cell-inner plexiform layer thickness (mGCIPLT) and CVF mean sensitivity (MS) was also assessed. For spatial correspondence, correlations between FAZ parameters and corresponding VD, mGCIPLT, and CVF-MS measurements were assessed at each hemiretina. RESULTS.A total of 126 OAG eyes and 40 controls were reviewed. Overall, FAZ parameters showed statistically significant correlations with VDs measured at the fovea, parafovea, and circumpapilla (FAZ area: r ¼ À0.603, À0.385, À0.256; P < 0.001, < 0.001, and 0.003, respectively). These correlations were observed regardless of the presence of CVF defects (all P < 0.05). FAZ size showed significant spatial correlations with VD, mGCIPLT, and CVF-MS measurements at each hemiretina.CONCLUSIONS. OCTA-derived FAZ area and perimeter showed statistically significant correlations with VDs measured at various retinal locations with spatial correspondence in OAG.

Section: Discussionsupporting

confidence: 77%

Section: Octa Image Acquisition and Processingmentioning

confidence: 99%

An Optical Coherence Tomography Angiography Study of the Relationship Between Foveal Avascular Zone Size and Retinal Vessel Density

Kwon

Choi²,

Shin

et al. 2018

“…Less but still satisfactory reliability was disclosed also for 12 3 12-mm angiocube at the same plexuses besides diabetic subgroup at all retina. As reported by other studies, 12 the interrater reliability was not as good for deep vascular plexus. Interestingly, good results were seen in the 3 3 3-mm scan, but not in the others.…”

Section: Discussionsupporting

confidence: 54%

“…Macular quantitative parameters vary across different instruments and techniques (i.e., manual versus automatic assessment); however, several studies demonstrated that they have a good inter-and intraoperator reliability in case of same machine, acquisition and postprocessing protocols. [7][8][9]11,12,23 Measurement at the superficial plexus is highly reliable, while manual demarcation at the deep plexus may be not easy due to less definite contours.…”

Section: Discussionmentioning

confidence: 99%

Macular Perfusion Parameters in Different Angiocube Sizes: Does The Size Matter in Quantitative Optical Coherence Tomography Angiography?

Rabiolo

Gelormini

Marchese

et al. 2018

PURPOSE. To investigate the macular quantitative parameters interchangeability of three different optical coherence tomography angiography (OCT-A) angiocubes (i.e., 3 3 3, 6 3 6, and 12 3 12 mm) on healthy subjects and patients affected by diabetic retinopathy (DR) and to assess the interrater reliability of such indices across the different scan protocols. METHODS.Retrospective study involving 20 eyes of healthy subjects and 20 eyes with DR. All eyes underwent swept-source OCT-A with 3 3 3-, 6 3 6-, and 12 3 12-mm angiocubes centered on the fovea. Foveal avascular zone (FAZ) area and vessel density on 3 3 3-, 6 3 6-, and 12 3 12-mm macular scans were calculated by three independent operators at all retina, superficial, deep, and choriocapillary vascular layers. Interchangeability and interrater reliabilities were estimated using intraclass correlation coefficient (ICC).RESULTS. Interscan reproducibility of FAZ area was very strong (ICC > 0.85) at every plexus. On the contrary, vessel density values significantly varied across different scan sizes (ICC < 0.51). Intrascan interrater reliability was high for all retina and superficial FAZ areas, while it was satisfactory at deep capillary plexus only for 3 3 3-mm scan.CONCLUSIONS. FAZ area at all plexuses is a robust parameter even if calculated on angiocubes with different size. However, interrater reliability is higher when measured in smaller scans. Conversely, vessel density results depend on the size of angiocube, although their interrater reliability is extremely high. Studies involving OCT-A should take into consideration that scan size may influence macular perfusion parameters and interrater reliability.

“…Manual measurement of FAZ area based on OCTA images at the superficial vascular network is a noninvasive, simple, and useful method for quantifying FAZ dimensions and architecture. [12][13][14][15][16][17] Clinical elements affecting FAZ area may include age, diabetic retinopathy (DR), and retinal vascular occlusive diseases.12,18-22 Foveal avascular zone circularity (roundness of the FAZ border) can also help characterize FAZ architecture, which can be reduced by vascular diseases in the macula, such as DR or retinal vein occlusion (RVO). 12,13,15,[17][18][19] Patients with microcirculatory deficiency involving the macula have been shown to have selective alteration in the FAZ area and circularity in the perifoveal region.…”

mentioning

confidence: 99%

Alterations of the Foveal Avascular Zone Measured by Optical Coherence Tomography Angiography in Glaucoma Patients With Central Visual Field Defects

Kwon

Choi²,

Shin

et al. 2017

Citation: Kwon J, Choi J, Shin JW, Lee J, Kook MS. Alterations of the foveal avascular zone measured by optical coherence tomography angiography in glaucoma patients with central visual field defects. Invest Ophthalmol Vis Sci. 2017;58:163758: -164558: . DOI: 10.1167 PURPOSE. To investigate whether the area and shape of the foveal avascular zone (FAZ) as assessed by optical coherence tomography angiography (OCTA) are altered in glaucomatous eyes with central visual field defects (CVFDs). METHODS.A total of 78 patients with open-angle glaucoma with central or peripheral visual field defects (PVFDs) confined to a single hemifield were studied retrospectively. Foveal avascular zone area and circularity were measured using OCTA images from the superficial retinal layer. Central retinal visual field (VF) sensitivity using Swedish Interactive Threshold Algorithm 24-2 VF and macular ganglion cell-inner plexiform layer (mGCIPL) thickness were measured. The FAZ area between VF-affected hemimacular segments and VF-unaffected hemimacular segments in eyes with CVFDs and matched hemimacular segments of eyes with PVFDs were compared. Factors associated with the presence and severity of CVFD at initial presentation were determined. RESULTS.Eyes with CVFDs showed a significantly larger FAZ area, lower FAZ circularity, and lower mGCIPL thickness than the PVFD group. The mean hemi-FAZ area of VF-affected hemimaculas in eyes with CVFDs was significantly larger than that of the PVFD group (0.256 6 0.07 mm 2 vs. 0.184 6 0.07 mm 2 ) and the VF-unaffected hemimaculas of the CVFD group (0.179 6 0.06 mm 2 ; P < 0.05). Age, mean deviation, mGCIPL thickness, FAZ area, and circularity were associated with CVFDs (P < 0.05).CONCLUSIONS. Microcirculatory alterations in the perifovea are spatially correlated with central VF loss. Loss of FAZ circularity was significantly associated with presence of CVFD, whereas FAZ area was significantly associated with severity of CVFD.Keywords: foveal avascular zone, central visual field defects, optical coherence tomography angiography G laucoma is a leading cause of irreversible blindness and is characterized by progressive retinal ganglion cell (RGC) death and axonal loss.1,2 Ocular blood flow (OBF) impairment and/or abnormal microcirculation along with elevated IOP may play an important role in glaucoma, particularly in normaltension glaucoma (NTG) [3][4][5][6][7] ; however, the exact pathogenesis of glaucoma is still unknown. To assess the vascular integrity of OBF, different types of imaging modalities have been introduced, including fluorescein angiography (FA), Heidelberg retina flowmeter, and color Doppler. Although FA remains the gold standard for detecting vascular pathology in the retina, it is invasive and requires exposure to an exogenous contrast agent. Moreover, the axial and lateral resolution of FA allows for limited visualization of capillaries, especially in macula in which there are overlapping capillary networks. 8 Recently, noninvasive retinal microvascular imaging has become availab...