Determinants of Quantitative Optical Coherence Tomography Angiography Metrics in Patients with Diabetes

Abstract

Early microvascular damage in diabetes (e.g. capillary nonperfusion and ischemia) can now be assessed and quantified with optical coherence tomography-angiography (OCT-A). The morphology of vascular tissue is indeed affected by different factors; however, there is a paucity of data examining whether OCT-A metrics are influenced by ocular, systemic and demographic variables in subjects with diabetes. We conducted an observational cross-sectional study and included 434 eyes from 286 patients with diabetes. Foveal avascular zone (FAZ) area, FAZ circularity, total and parafoveal vessel density (VD), fractal dimension (FD), and vessel diameter index (VDI) from the superficial capillary plexus OCT-angiogram were measured by a customized automated image analysis program. We found that diabetic retinopathy (DR) severity was associated with increased FAZ area, decreased FAZ circularity, lower VD, lower FD, and increased VDI. Enlarged FAZ area was correlated with shorter axial length and thinner central subfield macular thickness. Decreased FAZ circularity was correlated with a reduction in visual function. Decreased VD was correlated with thinner macular ganglion-cell inner plexiform layer. Increased VDI was correlated with higher fasting glucose level. We concluded that the effects of ocular and systemic factors in diabetics should be taken into consideration when assessing microvascular alterations via OCT-A.

Repeatability, interocular correlation and agreement of quantitative swept-source optical coherence tomography angiography macular metrics in healthy subjects

“…The details of the algorithm were reported in our previous publication 10. The following parameters were calculated: The area of FAZ was measured by counting the total number of pixels within FAZ in a scale multiplying the dimension of a pixel.…”

“…Existing studies have reported enlarged foveal avascular zone (FAZ) area in retinal ischaemic diseases such as diabetic retinopathy (DR)10 and retinal vascular obstruction (RVO)11; decreased FAZ area in retinopathy of prematurity12; decreased vessel density in DR10 and glaucoma13; lower fractal dimension in RVO,11 DR10 and uveitis eyes14; increased vessel diameter index (VDI) in RVO11 and DR10; and decreased FAZ circularity in glaucoma15 and DR 10. These studies demonstrate that quantitative OCTA metrics may provide useful information for the diagnosis of ocular diseases potentially.…”

Relationship of intercapillary area with visual acuity in diabetes mellitus: an optical coherence tomography angiography study

“…En-face OCT-A images are imported into an automated customised MATLAB programme for image analysis, which has been described previously 10. The area of the FAZ (mm 2 ) was calculated by counting total numbers of pixels within the region in scale.…”

“…FAZ circularity was defined as the ratio of FAZ area and the theoretical area, which was a re-projected circle with the same perimeter as FAZ area, with a range of 0.0 to –1.0 10. VD was calculated as the percentage of area not defined as non-perfusion regions (dark areas from the binarized image >0.02 mm)2 20 over total area within the parafoveal region (an annulus with an outer diameter of 3 mm and an inner diameter of 1 mm) 10. ICA was determined by detecting the connected components of the dark areas from the binarized image within the parafoveal region.…”

“…ICA was quantified by two metrics: the mean of the 10 largest areas including FAZ (ICA10_FAZ) and excluding FAZ (ICA10_excFAZ). Intrasession (repeat OCT-A imaging in the same visit) and intersession (repeat OCT-A imaging in other visit within 2 weeks) reliability assessments of FAZ circularity, FAZ area and VD measurement using our customised programme were reported before in a subset of 30 subjects with diabetes 10. For ICA metrics, the intraclass correlation coefficients for intrasession repeatability of the ICA10_FAZ and ICA_excFAZ were 0.764 (95% CI 0.562 to 0.881) and 0.786 (95% CI 0.597 to 0.892), respectively, while the ICCs for intersession reproducibility of the ICA10_FAZ and ICA_excFAZ were 0.750 (95% CI 0.539 to 0.873) and 0.744 (95% CI 0.528 to 0.869), respectively.…”