Different effect of media opacity on automated and manual measurement of foveal avascular zone of optical coherence tomography angiographies

Factors affecting optical coherence tomography angiography signal strength index in patients receiving intravitreal injection treatment

PURPOSE

To investigate the clinical factors affecting optical coherence tomography angiography (OCTA) signal strength index (SSI) and its change after intravitreal injection treatment in patients with retinal disorders.

METHODS

OCTA data from 186 eyes of 166 patients with various retinal disorders including age-related macular degeneration, diabetic macular edema (DME), and retinal vein occlusions who received intravitreal injections were analyzed. The associations between SSI and clinical factors, including age, best-corrected visual acuity (BCVA), media opacity severity, and central macular thickness (CMT), were evaluated both before and after injection.

RESULTS

After injection, BCVA improved and CMT decreased significantly, and SSI increased significantly (p = 0.030). BCVA showed a significant positive correlation with media opacity severity before and after injection and with CMT only before injection. In the multivariate analysis, age, presence of DME, BCVA, and media opacity severity were negatively associated with SSI both before and after injection, while CMT was negatively associated with SSI only before injection. After injection, a negative correlation was found between SSI change and both BCVA and CMT change.

CONCLUSION

Our findings suggest that OCTA SSI is influenced by various clinical factors, including age, visual acuity, media opacity severity, and macular thickening, especially in cases of DME. The results also indicate that SSI may decrease in patients with macular disorders due to the presence of macular edema and the associated decrease in visual acuity. Therefore, it is crucial to consider these factors when interpreting OCTA data and ensure an adequate level of SSI.

Automatic Determination of the Center of Macular Hole Using Optical Coherence Tomography En Face Images

To evaluate the automated determination of the center of an idiopathic macular hole (MH) by using swept-source optical coherence tomography (OCT) images with new macro-based algorithms in ImageJ and to compare the difference between the MH center measurements obtained automatically and manually. This cross-sectional study included 39 eyes of 39 elderly individuals (22 women, 17 men) with stage 3 and 4 MH. The MH center was automatically determined using the ImageJ macro. The foveal center was also manually identified by two masked examiners using horizontal and vertical serial B-scan OCT angiography images. The mean age was 68.8 ± 8.3 years. After adjusting for the effect of magnification, the mean distance between the MH center determined manually by Examiner 1 and that determined automatically was 15.5 ± 9.9 µm. The mean distance between the two manually determined measurements of the MH center was 20.3 ± 19.7 µm. These two mean distance values did not differ significantly (Welch t-test, p = 0.27) and was non-inferior (p < 0.0001). The automated ImageJ-based method for determining the MH center was comparable to manual methods. This study showed that automated measurements were non-inferior to manual measurements, and demonstrated a substitutable usefulness, at least for use in clinical practice.

Optical cohorence tomography angiography findings in carotid artery stenosis

AIM

To investigate vascular density (VD) changes in the superficial (SCP) and deep capillary plexus (DCP), radial peripapillar capillary plexus (RPCP), Foveal avascular zone (FAZ) and thickness changes of peripapillary retinal nerve fiber layer (ppRNFL) and choroid (CT) using optical coherence tomography angiography (OCTA) ipsilateral eyes of patient with internal carotid artery stenosis (ICAS) and to compare the obtained values with kontralateral eyes of patients with İCAS and healthy individuals.

METHODS

This prospective cross-sectional case-control study was conducted in 43 patients with a diagnosis of unilateral ICAS and 47 age- and sex-matched healthy subjects. The patients were divided into three groups. Group 1 consisted of ipsilateral eyes of patients with ICAS, group 2 consisted of contralateral eyes of patients with CAS and group 3 comprised healthy individuals without ICAS, All participants underwent a comprehensive ophthalmologic examination including OCTA.

RESULTS

FAZ, Superficial parafoveal and superficial superior VD were significantly lower in group 1 compared to group 2 (p =  < 0.001, p = 0.018 and 0.021, respectively). Group 1 also had lower superficial superior (p = 0.038), superficial inferior (p = 0.034), deep superior (p = 0.034), and deep inferior (p = 0.012) VD compared to group 3. There was no significant difference between the groups in terms of ppRNFLT, whereas CT and RPC mean, superior, and inside-disc VD values were significantly lower in group 1 compared to both group 2 and 3 (p < 0.05).

CONCLUSION

OCTA measurements may be useful in preventing irreversible ocular complications by detecting early structural changes in patients with ICAS before the development of symptomatic ocular ischemic syndrome.

Optical coherence tomography angiography in healthy children: normative data and age-related changes in microvascular structure of the optic disk and macula

PURPOSE

To determine normative data and reference ranges according to age groups by measuring the foveal avascular zone (FAZ), superficial capillary plexus vascular density (SCP-VD), deep capillary plexus vascular density (DVP-VD), radial peripapillary capillary plexus vessel density (RPC-VD), and peripapillary retinal nerve fiber layer (ppRNFL) in healthy children and to determine the age and sex-related changes of these values.

METHODS

This prospective study included data from 370 eyes of 370 healthy children (202 girls, 168 boys) aged 7-18 years. Participants were divided into four groups according to their age. Optical coherence tomography angiography (OCTA) measurements were taken using AngioVue (Avanti; Optivue).

RESULTS

No statistically significant difference was observed in terms of FAZ, SCP-VD, DCP-VD, RPC-VD, and ppRNFL thickness values according to the age groups (except the RPC-VD superior) (p > 0.05 for all). VDs in all deep parafoveal regions in groups 1 and 2 were higher in girls. While FAZ values were higher in girls in all age groups (statistically significant in groups 1, 3, and 4), ad SPD and DPD values were higher in boys in all age groups (statistically significant in group 1 and 2 for SPD, and group 1 and 3 for DPD).

CONCLUSIONS

We report normal reference ranges for macula and disk vessel density and ppRNFL parameters in healthy children aged 7-18 years using OCTA. These normative values could be useful in diagnosing retina and optic disk disease early in childhood.

Application of Improved U-Net Convolutional Neural Network for Automatic Quantification of the Foveal Avascular Zone in Diabetic Macular Ischemia

OBJECTIVES

The foveal avascular zone (FAZ) is a biomarker for quantifying diabetic macular ischemia (DMI), to automate the identification and quantification of the FAZ in DMI, using an improved U-Net convolutional neural network (CNN) and to establish a CNN model based on optical coherence tomography angiography (OCTA) images for the same purpose.

METHODS

The FAZ boundaries on the full-thickness retina of 6 × 6 mm en face OCTA images of DMI and normal eyes were manually marked. Seventy percent of OCTA images were used as the training set, and ten percent of these images were used as the validation set to train the improved U-Net CNN with two attention modules. Finally, twenty percent of the OCTA images were used as the test set to evaluate the accuracy of this model relative to that of the baseline U-Net model. This model was then applied to the public data set sFAZ to compare its effectiveness with existing models at identifying and quantifying the FAZ area.

RESULTS

This study included 110 OCTA images. The Dice score of the FAZ area predicted by the proposed method was 0.949, the Jaccard index was 0.912, and the area correlation coefficient was 0.996. The corresponding values for the baseline U-Net were 0.940, 0.898, and 0.995, respectively, and those based on the description data set sFAZ were 0.983, 0.968, and 0.950, respectively, which were better than those previously reported based on this data set.

CONCLUSIONS

The improved U-Net CNN was more accurate at automatically measuring the FAZ area on the OCTA images than the traditional CNN. The present model may measure the DMI index more accurately, thereby assisting in the diagnosis and prognosis of retinal vascular diseases such as diabetic retinopathy.

[Retinal vascular network: Changes with aging and systemic vascular disease (cardiac and cerebral)]

For over 10 years, the description of the retinal microvascular network has benefited from the development of new imaging techniques. Automated retinal image analysis software, as well as OCT angiography (OCT-A), are able to highlight subtle, early changes in the retinal vascular network thanks to a large amount of microvascular quantitative data. The challenge of current research is to demonstrate the association between these microvascular changes, the systemic vascular aging process, and cerebrovascular and cardiovascular disease. Indeed, a pathophysiological continuum exists between retinal microvascular changes and systemic vascular diseases. In the Montrachet study, we found that a suboptimal retinal vascular network, as identified by the Singapore I Vessel Assessment (SIVA) software, was significantly associated with treated diabetes and an increased risk of cardiovascular mortality. In addition, we supplemented our research on the retinal vascular network with the use of OCT-A. In the EYE-MI study, we showed the potential role of quantitative characterization of the retinal microvascular network by OCT-A in order to assess the cardiovascular risk profile of patients with a history of myocardial infarction. A high AHA (American Heart Association) risk score was associated with low retinal vascular density independently of hemodynamic changes. Thus, a better understanding of the association between the retinal microvasculature and macrovascular disease might make its use conceivable for early identification of at-risk patients and to suggest a personalized program of preventative care. The retinal vascular network could therefore represent an indicator of systemic vascular disease as well as an interesting predictive biomarker for vascular events.

Evaluation of macular microvasculature and foveal avascular zone in patients with retinal vein occlusion using optical coherence tomography angiography

PURPOSES

To quantitatively evaluate the vessel density of macular microvasculature, choriocapillary, and foveal avascular zone (FAZ) in both eyes of patients with unilateral retinal vein occlusion (RVO) using the optical coherence tomography angiography (OCTA) compared with the normal controls.

METHODS

A retrospective review was conducted on 72 patients with unilateral RVO (72 eyes with RVO and 72 RVO fellow eyes) and 72 healthy individuals (72 normal control eyes). The 3 × 3 mm macular angiogram was acquired using the OCTA. The vessel densities of the retinal superficial capillary plexus (SCP), deep capillary plexus (DCP), and choriocapillary plexus (CCP) were measured, and FAZ was quantified.

RESULTS

The RVO eyes compared to their fellow eyes, and the fellow eyes compared to the normal controls, showed a significantly lower vessel density in both the SCP and DCP in the whole image and parafovea (P < 0.05) and the CCP (P < 0.05), except for the foveal region (P > 0.05). No significant differences between the RVO eyes and the fellow eyes in the FAZ area and perimeter (P > 0.05) were observed, while the acircularity index in the RVO eyes was significantly higher than the fellow eyes (P < 0.05). Additionally, the FD-300 in the RVO eyes was significantly lower than their fellow eyes (P < 0.05).

CONCLUSIONS

The OCTA reveals that the macular microvasculature of the RVO fellow eyes can be impaired in both the superficial and deep retinal layer as well as the choriocapillary, suggesting the influence of systemic factors in the development of RVO.

Quantification of retinal microvascular parameters by severity of diabetic retinopathy using wide-field swept-source optical coherence tomography angiography

PURPOSE

To investigate the diagnostic utility of microvascular parameters for grading the severity of diabetic retinopathy (DR) with a range of views using wide-field swept-source optical coherence tomography angiography (SS-OCTA).

METHODS

This retrospective study grouped 235 eyes with diabetes into the five grades: diabetes without retinopathy (no-DR), mild non-proliferative DR (NPDR), moderate NPDR, severe NPDR, and proliferative DR (PDR). Foveal avascular zone (FAZ) metrics, vessel density (VD), and the capillary nonperfusion area (NPA) were quantified with a customized, semiautomatic software algorithm. Regions of interest were selected from three rectangular fields of different sizes (i.e., 3 × 3 mm², 6 × 6 mm², and 10 × 10 mm²), perpendicular to the fovea-optic disc axis.

RESULTS

NPA obtained from the 6 × 6mm² and 10 × 10mm² areas was the only discriminating parameter for the three NPDR stages. ROC curve analysis revealed that NPA from the 10 × 10mm² field exhibited the best performance for grading DR into five stages. The NPA cutoff values were 3.7% (area under the curve (AUC): 0.91), 4.7% (AUC: 0.94), 9.3% (AUC: 0.94), and 21.4% (AUC: 0.90) for grading no-DR, mild from moderate NPDR, moderate from severe NPDR, and severe NPDR from PDR, respectively.

CONCLUSIONS

Increasing DR severity as assessed by conventional grading systems is accompanied with increasing retinal ischemia on SS-OCTA. NPA measured from the larger 10 × 10 mm² scan area showed the highest sensitivity for determining five-grade DR severity. In the future, the addition of quantitative NPA may provide a more clinically feasible DR grading system.

Retinal Neurovascular Impairment in Non-diabetic and Non-dialytic Chronic Kidney Disease Patients

Background: Widespread neural and microvascular injuries are common in chronic kidney disease (CKD), increasing risks of neurovascular complications and mortality. Early detection of such changes helps assess the risks of neurovascular complications for CKD patients. As an extension of central nervous system, the retina provides a characteristic window to observe neurovascular alterations in CKD. This study aimed to determine the presence of retinal neurovascular impairment in different stages of CKD. Methods: One hundred fifteen non-diabetic and non-dialytic CKD patients of all stages and a control group of 35 healthy subjects were included. Retinal neural and microvascular parameters were obtained by optical coherence tomography angiography (OCTA) examination. Results: CKD 1-2 group (versus control group) had greater odds of having decreased retinal ganglion cell-inner plexiform layer thickness (GC-IPLt) (odds ratio [OR]: 0.92; 95% confidence interval [CI]: 0.86-0.98), increased ganglion cell complex-focal loss volume (GCC-FLV) (OR: 3.51; 95% CI: 1.27-9.67), and GCC-global loss volume (GCC-GLV) (OR: 2.48; 95% CI: 1.27-4.82). The presence of advanced stages of CKD (CKD 3-5 group versus CKD 1-2 group) had greater odds of having decreased retinal vessel density in superficial vascular plexus (SVP)-WholeImage (OR: 0.77, 95% CI: 0.63-0.92), SVP-ParaFovea (OR: 0.83, 95% CI: 0.71-0.97), SVP-ParaFovea (OR: 0.76, 95% CI: 0.63-0.91), deep vascular plexus (DVP)-WholeImage (OR: 0.89, 95% CI: 0.81-0.98), DVP-ParaFovea (OR: 0.88, 95% CI: 0.78-0.99), and DVP-PeriFovea (OR: 0.90, 95% CI: 0.83-0.98). Besides, stepwise multivariate linear regression among CKD patients showed that β2-microglobulin was negatively associated with GC-IPLt (β: -0.294; 95% CI: -0.469 ∼ -0.118), and parathyroid hormone was positively associated with increased GCC-FLV (β: 0.004; 95% CI: 0.002∼0.006) and GCC-GLV (β: 0.007; 95% CI: 0.004∼0.01). Urine protein to creatinine ratio was positively associated with increased GCC-FLV (β: 0.003; 95% CI: 0.001∼0.004) and GCC-GLV (β: 0.003; 95% CI: 0.001∼0.006). Conclusion: Retinal neuronal impairment is present in early stages of CKD (stages 1-2), and it is associated with accumulation of uremic toxins and higher UACR, while retinal microvascular hypoperfusion, which is associated with worse eGFR, was only observed in relatively advanced stages of CKD (stages 3-5). The results highlight the importance of monitoring retinal neurovascular impairment in different stages of CKD.

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.