Interchangeability of retinal perfusion indices in different-sized angiocubes: An optical coherence tomography angiography study in diabetic retinopathy

Retinal Alterations as Potential Biomarkers of Structural Brain Changes in Alzheimer’s Disease Spectrum Patients

Retinal imaging being a potential biomarker for Alzheimer’s disease is gradually attracting the attention of researchers. However, the association between retinal parameters and AD neuroimaging biomarkers, particularly structural changes, is still unclear. In this cross-sectional study, we recruited 25 cognitively impaired (CI) and 21 cognitively normal (CN) individuals. All subjects underwent retinal layer thickness and microvascular measurements with optical coherence tomography angiography (OCTA). Gray matter and white matter (WM) data such as T1-weighted magnetic resonance imaging and diffusion tensor imaging, respectively, were also collected. In addition, hippocampal subfield volumes and WM tract microstructural alterations were investigated as classical AD neuroimaging biomarkers. The microvascular and retinal features and their correlation with brain structural imaging markers were further analyzed. We observed a reduction in vessel density (VD) at the inferior outer (IO) sector (p = 0.049), atrophy in hippocampal subfield volumes, such as the subiculum (p = 0.012), presubiculum (p = 0.015), molecular_layer_HP (p = 0.033), GC-ML-DG (p = 0.043) and whole hippocampus (p = 0.033) in CI patients. Altered microstructural integrity of WM tracts in CI patients was also discovered in the cingulum hippocampal part (CgH). Importantly, we detected significant associations between retinal VD and gray matter volumes of the hippocampal subfield in CI patients. These findings suggested that the retinal microvascular measures acquired by OCTA may be markers for the early prediction of AD-related structural brain changes.

Aqueous angiopoietin-like levels correlate with optical coherence tomography angiography metrics in diabetic macular edema

AIM

To quantitatively detect aqueous levels of angiopoietin-like (ANGPTL)3, ANGPTL4, and ANGPTL6 and investigate their correlation with optical coherence tomography angiography (OCTA) findings in patients with diabetic macular edema (DME).

METHODS

This cross-sectional study included 23 patients (27 eyes) with type 2 diabetes and 16 control subjects (20 eyes). All patients underwent OCTA imaging and ultra-wide field fundus photography. Diabetic patients were categorized into two groups according to the presence or absence of diabetic retinopathy (DME group, 14 patients, 16 eyes); and non-diabetic retinopathy (NDR) group, 9 patients, 11 eyes, respectively. Aqueous levels of ANGPTL3, ANGPTL4, and ANGPTL6 were assessed using suspension array technology, and foveal-centered 3×3 mm² OCTA scans were automatically graded to determine the central, inner, and full vessel density (CVD, IVD, FVD); central, inner, and full perfusion density (CPD, IPD, FPD), foveal avascular zone (FAZ) area, FAZ perimeter, and FAZ circularity index (FAZ-CI) on superficial capillary plexuses. Additionally, central subfield thickness (CST), cube volume (CV), and cube average thickness (CAT) were measured in a model of macular cube 512×128.

RESULTS

Aqueous ANGPTL3 levels were not significantly different among the three groups (P>0.05). ANGPTL4 levels were significantly higher in the DME group than the control and NDR groups (P<0.0001 and P<0.001), while ANGPTL6 levels were significantly higher in the DME group than the control group (P<0.05). In the whole cohort, the aqueous ANGPTL3 levels correlated negatively with the IVD, FVD, IPD, and FPD, and positively with the CV and CAT. The aqueous ANGPTL4 levels correlated negatively with the CVD, IVD, FVD, CPD, IPD, and FPD, and positively with the FAZ perimeter, CST, CV, and CAT. The aqueous ANGPTL6 levels correlated negatively with the IVD, FVD, IPD, FPD, FAZ-CI and positively with CST, CV, CAT.

CONCLUSION

ANGPTL4 and ANGPTL6 may be associated with vascular leakage in DME and may represent good targets for DME therapy. In addition, OCTA metrics may be useful for evaluating macular ischemia in DME.

Intraretinal microvascular changes after ERM and ILM peeling using SSOCTA

BACKGROUND

To prospectively investigate retinal vascular changes in patients undergoing epiretinal membrane (ERM) and internal limiting membrane (ILM) peeling using swept source optical coherence tomography angiography (SSOCTA).

METHODS

Consecutive patients were grouped based on ERM severity and followed using SSOCTA up to month 3 after surgical intervention. Superficial and deep foveal avascular zone (s/dFAZ) as well as foveal and parafoveal vessel density (VD) were correlated with ERM severity and visual acuity. Differences between groups were evaluated.

RESULTS

Significant correlations were found between ERM severity and baseline sFAZ, dFAZ and best corrected visual acuity (BCVA), central retinal subfield thickness (CST) and ΔCST (r = -0.52, r = -0.43, r = -0.42, r = 0.58, r = 0.39; all p<0.05). Vascular flow parameters did not correlate with age, peeling size, pseudophakia or CST, but correlated with intraretinal cysts presence. No associations of BCVA with any of the OCTA parameters across time were found. Significant differences between ERM severity groups 1 and 2 were found for sFAZ at baseline (p = 0.005) and at the 3-month follow-up (p = 0.014), and for dFAZ at baseline (p = 0.017). Superficial foveal and parafoveal VD were not significantly different between groups (all p>0.05).

CONCLUSIONS

This study clearly shows that ERM severity based on ERM staging has to be taken into account when undertaking studies in patients with idiopathic ERM using SSOCTA. Further, specific changes in the superficial and deep retinal vasculature in eyes undergoing ERM and ILM peeling were found. However, the clinical usefulness and prognostic value for post-surgical treatment BCVA of the SSOCTA-derived variables (sFAZ and dFAZ area, as well as foveal and parafoveal VD) used remains questionable.

Improved Automated Foveal Avascular Zone Measurement in Cirrus Optical Coherence Tomography Angiography Using the Level Sets Macro

Purpose

To evaluate automated measurements of the foveal avascular zone (FAZ) using the Level Sets macro (LSM) in ImageJ as compared with the Cirrus optical coherence tomography angiography (OCTA) inbuilt algorithm and the Kanno–Saitama macro (KSM).

Methods

The eyes of healthy volunteers were scanned four times consecutively on the Zeiss Cirrus HD-OCT 5000 system. The FAZ metrics (area, perimeter, and circularity) were measured manually and automatically by the Cirrus inbuilt algorithm, the KSM, and the LSM. The accuracy and repeatability of all methods and agreement between automated and manual methods were evaluated.

Results

The LSM segmented the FAZ with an average Dice coefficient of 0.9243. Compared with the KSM and the Cirrus inbuilt algorithm, the LSM outperformed them by 0.02 and 0.19, respectively, for Dice coefficients. Both the LSM (intraclass correlation coefficient [ICC] = 0.908; coefficient of variation [CoV] = 9.664%) and manual methods (ICC ≥ 0.921, CoV ≤ 8.727%) showed excellent repeatability for the FAZ area, whereas the other methods presented moderate to good repeatability (ICC ≤ 0.789, CoV ≥ 15.788%). Agreement with manual FAZ area measurement was excellent for both the LSM and KSM but not for the Cirrus inbuilt algorithm (LSM, ICC = 0.930; KSM, ICC = 0.928; Cirrus, ICC = 0.254).

Conclusions

The LSM exhibited greater accuracy and reliability compared to the KSM and inbuilt automated methods and may be an improved and accessible option for automated FAZ segmentation.

Translational Relevance

The LSM may be a suitable automated and customizable tool for FAZ quantification of Cirrus HD-OCT 5000 images, providing results comparable to those for manual measurement.