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Journal ArticleDOI

Quantifying Microvascular Abnormalities With Increasing Severity of Diabetic Retinopathy Using Optical Coherence Tomography Angiography.

TL;DR: Retinal and choriocapillaris vascular nonperfusion in OCTA is correlated significantly with disease severity in eyes with DR, and higher flow in the SCP may be an early marker of diabetic microvascular changes before clinical signs of DR.
Abstract: Purpose We quantified retinal and choriocapillaris microvascular changes in healthy control eyes and different stages of diabetic retinopathy (DR) using optical coherence tomography angiography (OCTA). Methods This retrospective cross-sectional study included 137 eyes of 86 patients with different stages of DR and 44 eyes of 26 healthy age-matched controls. Participants were imaged with a commercial OCTA device (RTVue-XR Avanti). We analyzed the superficial (SCP) and deep (DCP) retinal capillary plexus, the full retina, and choriocapillaris for the following OCTA parameters: foveal avascular zone, vessel density, percent area of nonperfusion (PAN), and adjusted flow index (AFI). We adjusted for age, sex, and the correlation between eyes of the same study participant in our statistical models. Results All OCTA parameters showed a significant linear correlation with DR severity (P < 0.05) in the univariate models except for AFI measured in the SCP and these correlations remained significant after correcting for covariates. Compared to the other capillary layers, the AFI at the DCP decreased significantly with DR severity. When comparing individual disease severity groups as categories, eyes of subjects with diabetes without DR had significantly increased PAN and AFI in the SCP compared to healthy subjects (P < 0.05). Conclusions Retinal and choriocapillaris vascular nonperfusion in OCTA is correlated significantly with disease severity in eyes with DR. Higher flow in the SCP may be an early marker of diabetic microvascular changes before clinical signs of DR. The steep decline of blood flow in the DCP with increasing DR severity suggests that alterations at the DCP warrant further investigation.
Citations
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Journal ArticleDOI
TL;DR: A review of the salient histological and anatomical features of the choroid, essential for the proper interpretation of in vivo imaging, is followed by a discussion of the fundamental principles of OCTA and the application of this advanced imaging modality to study and understand the Choroid.

217 citations

Journal ArticleDOI
TL;DR: In this article, the relationship of OCT angiography (OCTA) metrics to diabetic retinopathy (DR) progression and development of diabetic macular edema (DME) was investigated.

160 citations

Journal ArticleDOI
TL;DR: OCTA can identify preclinical DR before the manifestation of clinically apparent retinopathy in diabetic eyes, and suggested that OCTA might be a promising tool for regular screening of diabetic eyes for DR.
Abstract: To investigate changes in retinal vascular plexuses and choriocapillaris in patients with type 2 diabetes mellitus (DM2) without diabetic retinopathy (DR) and healthy controls using optical coherence tomography angiography (OCTA). A total of 71 DM2 and 67 healthy control subjects were included. All subjects underwent OCTA examination (RTVue-XR Avanti; Optovue, Fremont, CA, USA). Average vessel density in superficial capillary plexus (SCP), deep capillary plexus (DCP) and choriocapillaris, parafoveal vessel density in SCP and DCP, FAZ area (mm2) in SCP, microaneurysms and capillary nonperfusion were taken into analysis. Parafoveal vessel density in both SCP and DCP decreased in the eyes without clinical DR compared to normal controls (p < 0.001). Diabetic patients with no signs of DR also had a significant reduction in average vessel density of SCP, DCP and choriocapillaris (p < 0.001, p < 0.001 and p = 0.006, respectively). No significant difference was found in FAZ area of SCP between DM2 eyes and healthy controls (p = 0.253). The average vessel density of SCP and DCP is not correlated with HbA1c or serum creatinine in DM2 patients. Microaneurysms seen in OCTA but not in fundus examination were found in 8 out of the 71 (11.3%) diabetic eyes, and capillary nonperfusion was noted in 18 of 71 diabetic eyes. We demonstrated that OCTA can identify preclinical DR before the manifestation of clinically apparent retinopathy in diabetic eyes. DM2 patients without DR have SCP, DCP and choriocapillaris impairment. Our results suggested that OCTA might be a promising tool for regular screening of diabetic eyes for DR.

126 citations

Journal ArticleDOI
TL;DR: In this article, the authors compare perfused capillary density (PCD) in diabetic patients and healthy controls using optical coherence tomography angiography (OCTA), and demonstrate the potential of OCTA as a clinical tool for earlier objective detection of preclinical diabetic retinopathy.

100 citations

References
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Journal ArticleDOI
TL;DR: In this paper, a split-spectrum amplitude-decorrelation angiography (SSADA) was proposed to improve the signal-to-noise ratio (SNR) of flow detection.
Abstract: Amplitude decorrelation measurement is sensitive to transverse flow and immune to phase noise in comparison to Doppler and other phase-based approaches. However, the high axial resolution of OCT makes it very sensitive to the pulsatile bulk motion noise in the axial direction. To overcome this limitation, we developed split-spectrum amplitude-decorrelation angiography (SSADA) to improve the signal-to-noise ratio (SNR) of flow detection. The full OCT spectrum was split into several narrower bands. Inter-B-scan decorrelation was computed using the spectral bands separately and then averaged. The SSADA algorithm was tested on in vivo images of the human macula and optic nerve head. It significantly improved both SNR for flow detection and connectivity of microvascular network when compared to other amplitude-decorrelation algorithms.

1,507 citations

Journal Article
TL;DR: In this paper, a split-spectrum amplitude-decorrelation angiography (SSADA) was proposed to improve the signal-to-noise ratio (SNR) of flow detection.
Abstract: Amplitude decorrelation measurement is sensitive to transverse flow and immune to phase noise in comparison to Doppler and other phase-based approaches. However, the high axial resolution of OCT makes it very sensitive to the pulsatile bulk motion noise in the axial direction. To overcome this limitation, we developed split-spectrum amplitude-decorrelation angiography (SSADA) to improve the signal-to-noise ratio (SNR) of flow detection. The full OCT spectrum was split into several narrower bands. Inter-B-scan decorrelation was computed using the spectral bands separately and then averaged. The SSADA algorithm was tested on in vivo images of the human macula and optic nerve head. It significantly improved both SNR for flow detection and connectivity of microvascular network when compared to other amplitude-decorrelation algorithms.

1,151 citations

Journal ArticleDOI
TL;DR: Once the authors have chosen to compare vision as a ratio using a reference visual angle (20/20), a geometric progression results and a geometric mean must be calculated for a meaningful result.
Abstract: C alculating the average visual acuity and standard deviation on a series of patients is not difficult , but has been done incorrectly in most studies. 1 The basic problem relates to the difference between the arithmetic and geometric mean for a set of numbers. For the correct average visual acuity, the geometric mean must be used, which gives significantly different values than the arithmetic mean. Modern visual acuity charts are designed so that the letter sizes on each line follow a geometric progression (ie, change in a uniform step on a logarithmic scale). 2-4 The accepted step size has been chosen to be 0.1 log unit steps, which is equivalent to letter sizes changing by a factor of 1.2589 between lines. This standard gave rise to the LogMAR (log of the minimum angle of resolution) notation, as shown in Table 1. A geometric progression of lines on the visual acuity chart was chosen because it parallels the way our visual system functions. If patient #1 has a visual acuity of 20/20 and patient #2 has a visual acuity of 20/40, we conclude that patient #1 has two times better visual acuity than patient #2 because he or she can recognize a letter twice as small. Once we have chosen to compare vision as a ratio using a reference visual angle (20/20), a geometric progression results and a geometric mean must be calculated for a meaningful result. Notice in Table 1 that the only values that increase linearly are the line numbers and the LogMar notation. The Snellen acuity, decimal acuity, and visual angle all increase by the geometric factor of 1.2589. Once we decide that equal steps in visual acuity measurement are geometric and not arithmetic , we must use the appropriate geometric mean to compute the correct average (Figure). In Table 1 and the Figure, we see that line 0 is the 20/20 Snellen acuity that corresponds to the LogMAR value zero, since 20/20 is the standard. We also see that line 10 is the 20/200 Snellen visual acuity that corresponds to a LogMAR value of +1.00 (ten times or 1 log unit worse than 20/20). Intuitively, it would appear that halfway between line 0 and line 10 would be line 5, or 20/63. This is the correct average, because geometrically it is halfway between 20/200 and 20/20. The two incorrect methods would be to take the arithmetic …

982 citations


"Quantifying Microvascular Abnormali..." refers methods in this paper

  • ...Monocular best-corrected visual acuity (BCVA) was determined for all subjects using Snellen eye charts and converted to the logMAR as described previously.(18) Patients were graded as having hypertension based on review of their electronic medical records....

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Journal ArticleDOI
TL;DR: Noteworthy has been the predominant localization of the diabetic microaneurysms in the central and paracentral regions, their random distribution, and their association with punctate hemorrhages and "exudates" in the deep retina.
Abstract: It is generally held that microaneurysms constitute the characteristic lesion of diabetic retinopathy. First observed by MacKenzie and Nettleship in 1879, 1 the microaneurysms were rediscovered by Ballantyne and Loewenstein in 1943 2 and have been described by numerous clinicians and pathologists since that time. Noteworthy has been the predominant localization of the diabetic microaneurysms in the central and paracentral regions, their random distribution, and their association with punctate hemorrhages and "exudates" in the deep retina. It has also been assumed that the microaneurysms and other evidence of angiopathy in diabetic retinas have a bearing on the glomerular changes in diabetic nephropathy 3-5 and that a clarification of the one might yield useful information for the other. As must be evident from the many reviews which have appeared in recent years, 6-12 the pathogenesis of retinal microaneurysms has been a subject of wide speculation based on some firm evidence but

715 citations


"Quantifying Microvascular Abnormali..." refers background in this paper

  • ...Histopathology has shown that degeneration of the retinal capillary pericytes and endothelial cells are early and seemingly invariable features of DR.1,2 The loss of these cells leads to acellular capillaries with impaired or absent perfusion.3 The resulting ischemia causes an upregulation of angiogenic signaling molecules, including VEGF and erythropoietin,4 which increase vascular permeability and ultimately promote proliferative diabetic retinopathy (PDR).5 A clinical understanding of the changes at the microvascular level could provide important information regarding the perfusion status of the retina during the different stages of DR and the likelihood of developing more severe retinopathy....

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  • ...Retinal and choriocapillaris vascular nonperfusion in OCTA is correlated significantly with disease severity in eyes with DR. Higher flow in the SCP may be an early marker of diabetic microvascular changes before clinical signs of DR....

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  • ...This decreased flow in the DCP may be an important topic for future studies exploring visual function in DR, as we have demonstrated recently a significant impact of DCP nonperfusion on the integrity of the photoreceptors.36,37 We introduced PAN as a new OCTA parameter, which, in its essence, is an inverse approach to vessel density and serves as a quantitative marker for the nonflow area in OCTA.21 Quantification of nonperfused areas (i.e., nonflow area) has been shown to be sensitive to early capillary closure in DR.15,38 Furthermore, since there was no vessel density algorithm for the choriocapillaris in the AngioVue software, calculating PAN allowed us to quantify choriocapillaris nonperfusion....

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  • ...The ability of OCTA to visualize the three-dimensional capillary layers with high resolution has allowed investigators to explore the capillary layers that are most affected in DR.6–8 Previous qualitative studies in DR have demonstrated that OCTA is capable of delineating retinal capillary nonperfusion with better resolution than conventional fluorescein angiography.9–11 Other studies have found decreased capillary density in patients with DR compared to healthy controls, as well as an association between reduced capillary density and worsening DR.12,13 Furthermore, the ability of OCTA to distinguish healthy eyes from eyes with varying levels of DR severity was demonstrated through the use of an automated algorithm for measuring avascular areas in the macula.14,15 While the studies described provide important information regarding the use of OCTA and have furthered our understanding of the vascular changes associated with DR, they have been limited to small cohorts and comparisons between only two study groups....

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  • ...In this study, we evaluated the correlation between retinal and choriocapillaris microvascular changes on OCTA and disease severity in eyes with DR....

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