Foveal Avascular Zone Diameter and Sickle Cell Disease

Abstract

background/aims To 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). Methods This is a multi-institutional retrospective study of patients with various stages of SCR compared with healthy controls. Parafoveal OCT-A images obtained using a commercial spectral domain-OCT system were reviewed. Foveal-centred 3×3 mm full vascular slab OCT-As were used for image processing and data analysis. FAZ area, perimeter, and acircularity index were determined on the OCT-A image after manual delineation of the FAZ border. Quadrant-based parafoveal capillary density and per cent area deviating from normal distribution were also measured. results Fifty-two patients with SCR (33 non-proliferative and 19 proliferative) and 20 age and race-matched healthy controls were included. One randomly selected eye per study participant was analysed. FAZ perimeter and acircularity index were significantly greater in SCR eyes when compared with the controls. While parafoveal capillary density was significantly lower, per cent area deviated from normal distribution was significantly higher in SCR eyes than that of the control. However, no statistically significant difference between the two SCR stages was observed. In quadrant-based analysis, the temporal quadrant showed greater parafoveal capillary dropout due to SCR, with the most profound effect in patients with proliferative SCR. Conclusions Abnormal FAZ morphology and altered parafoveal capillary perfusion were found in patients with SCR. Our customised OCT-A image analysis method uniquely highlights significant quantitative alterations in perfusion density mapping in a qualitative display, with minimal obscuration of OCT-A image detail.

Assessing the Accuracy of Foveal Avascular Zone Measurements Using Optical Coherence Tomography Angiography: Segmentation and Scaling

“…8 The FAZ is enlarged in patients with sickle cell disease. 9 In addition, retinal vascular changes around the FAZ also occur early in diabetes mellitus with capillary dropout occurring even before the onset of retinopathy, 10,11 leading to a significant increase in the size of the FAZ. Furthermore, FAZ size is correlated with visual acuity in patients with diabetic retinopathy, 12 suggesting that assessment of the FAZ could be a useful biomarker for studying diabetic patients.…”

Automated Quantitative Analysis of Retinal Microvasculature in Normal Eyes on Optical Coherence Tomography Angiography

“…5,6 FAZ borders are defined from the perifoveal capillary arcade, which consists of a ring of interconnected capillaries, formed by the superficial and deep vascular plexuses at the margin of the fovea. 3,7 The fovea centralis of the human provides high-resolution vision, and significant capillary dropout from this region, due to several retinal vascular diseases [8][9][10] , may cause severe visual loss. For this reason the perifoveal capillary network and FAZ have been studied in vitro and in vivo, using various methods, including histological techniques, high contrast entoptic view, fluorescein angiography (FA), and high-resolution imaging tools, such as adaptive optics and confocal scanning laser ophthalmoscopy.…”

Foveal Avascular Zone in Idiopathic Juxtafoveolar Telangiectasia

“…The mean FAZ diameter was determined to be 0.56 mm by the trypsin digestion method [9], and 0.25 mm [10] or 2.04° [11] by entoptic methods. Using fluorescein angiography, the mean FAZ diameter was (in disk diameter) 0.32 [1], 0.34 [12], (in mm) 0.20 [10], 0.53 [13], 0.61 [4,13], 0.73 [3], while the mean FAZ area was 0.231 [14] and 0.35 mm2 [3]. Bird and Weale [10] initially demonstrated that blood vessels were common in the center of the fo vea.…”

“…This zone (FAZ) is polygonal in contour and its size reflects the microcapillary foveal circulation. The FAZ is small in retinopathy of prematurity [1] and posterior microphthalmos [2], while it is enlarged in certain vaso-occlusive diseases, such as diabetic retinopathy [3], sickle cell retinopathy [4,5], retinal branch vein occlusions and talc retinopathy [6]. The present study is aimed at measuring the area of the FAZ and analyzing the juxtafoveolar microaneurysmal distribution in IJFT.…”