Optical Coherence Tomography Angiography of Retinal Vein Occlusion

Optical Coherence Tomography Angiography: Clinical Utility and Future Directions

Purpose

This work aims to review the principles of optical coherence tomography angiography (OCTA), to survey its clinical utility, and to highlight the strengths of this technology as well as barriers to adoption.

Methods

A literature review with editorial discussion of the current applications for OCTA is presented.

Results

There have been recent advances in multiple domains in OCTA imaging, including devices, algorithms, and new observations pertaining to a range of pathologies. New devices have improved the scanning speed, signal-to-noise ratio, and spatial resolution and offer an increased field of view. New algorithms have been proposed to optimize image processing and reduce artifacts. Numerous studies employing OCTA have been published describing changes to the microvasculature in diabetic retinopathy, age-related macular degeneration, central serous chorioretinopathy, retinal vein occlusion, and uveitis.

Conclusions

OCTA provides noninvasive, high-resolution volumetric scans of the retinal and choroidal vasculature. OCTA can provide valuable data to augment traditional dye-based angiography in a range of chorioretinal diseases.

Altered White Matter Integrity in Patients with Retinal Vein Occlusion: A Diffusion Tensor Imaging and Tract-Based Spatial Statistics Study

Background

To investigate microstructural alterations of white matter in retinal vein occlusion (RVO) patients by tract-based spatial statistics (TBSS) and diffusion tensor imaging (DTI). Material/Methods. DTI was performed on 14 RVO patients and 14 normal controls (HCs). We measured and recorded fractional anisotropy (FA) and radial diffusivity (RD) of white matter fibers and classified them through the receiver operating characteristic (ROC) curve and correlation analysis, respectively.

Results

The mean FA value of white matter in RVO patients is lower than the HCs, and the mean RD value in RVO patients increased, especially in the bilateral posterior thalamic, bilateral sagittal stratum, body of corpus callosum, cingulum, and fornix. The ROC curve of different brain regions showed high accuracy. Moreover, the mean FA and RD values were significantly correlated with visual and psychological disorders.

Conclusion

TBSS could be regarded as an important method to reveal the alterations of white matter in RVO patients, indicating the underlying neurological mechanism of the RVO.

Subclinical retinal angiopathy associated with hereditary transthyretin amyloidosis - assessed with optical coherence tomography angiography

BACKGROUND

Retinal angiopathy is a known ocular manifestation of hereditary transthyretin amyloidosis (ATTRv). Optical coherence tomography angiography (OCT-A) is a recent noninvasive imaging technique, used in other retinal vascular diseases. Our purpose was to analyse subclinical changes in retinal vessels, with OCT-A, in patients with ATTRv amyloidosis.

METHODS

Observational cross-sectional study in Centro Hospitalar e Universitário do Porto in the cohort of patients with genetic diagnosis of ATTRv. Patients were included if they had just one eye with scalloped iris (the other eye without scalloped iris), postulating eyes were at different stages, in the same patient. Patients were excluded if they had other manifestations of ocular ATTRv amyloidosis, namely clinical retinal angiopathy and/or vitreous opacities. The group of eyes with scalloped iris were compared with eyes without scalloped iris, using paired tests. Values are shown as Δ = mean difference between groups; p = p-value, d = Cohen's d for effect size measurement.

RESULTS

Twenty-four patients (24 eyes in each group) were included. Mean age was 46.5 ± 5.0 years. Eyes with scalloped iris showed attenuated retinal vascular network: larger foveal avascular zone (FAZ) area (Δ = +0.02 mm², p = 0.002, d = 0.70); decreased foveal vascular density (Δ = -3.57%, p = 0.001, d = -0.75); superficial (Δ = -1.50%, p = 0.049, d = -0.43) and deep (Δ = -2.53%, p = 0.023, d = -0.50) plexus vascular density. Acircularity index was superior in scalloped iris eyes (Δ = 0.04, p = 0.004, d = -0.65), representing an abnormal FAZ morphology.

CONCLUSION

Scalloped iris in ATTRv eyes are associated with a more advanced subclinical retinal angiopathy, than eyes without scalloped iris. Our results identify for the first time and in vivo, early changes in retinal vessels in ATTRv amyloidosis. Henceforward, OCT-A may play a role in the evaluation of ATTRv patients oculopathy and the effectiveness of future eye targeting treatments.

A practical guide to optical coherence tomography angiography interpretation

Background

Optical coherence tomography angiography (OCTA) can image the retinal vasculature in vivo, without the need for contrast dye. This technology has been commercially available since 2014, however, much of its use has been limited to the research setting. Over time, more clinical practices have adopted OCTA imaging. While countless publications detail OCTA’s use for the study of retinal microvasculature, few studies outline OCTA’s clinical utility.

Body

This review provides an overview of OCTA imaging and details tips for successful interpretation. The review begins with a summary of OCTA technology and artifacts that arise from image acquisition. New methods and best practices to prevent image artifacts are discussed. OCTA has the unique ability among retinovascular imaging modalities to individually visualize each retinal plexus. Slabs offered in standard OCTA devices are reviewed, and clinical uses for each slab are outlined. Lastly, the use of OCTA for the clinical interpretation of retinal pathology, such as diabetic retinopathy and age-related macular degeneration, is discussed.

Conclusion

OCTA is evolving from a scientific tool to a clinical imaging device. This review provides a toolkit for successful image interpretation in a clinical setting.

Reliability of foveal avascular zone measurements in eyes with retinal vein occlusion using optical coherence tomography angiography

BACKGROUND

To evaluate the reliability of foveal avascular zone (FAZ) area measurements using optical coherence tomography angiography (OCTA) in eyes with retinal vein occlusion (RVO).

METHODS

Twenty-five OCTA exams of patients with RVO were evaluated retrospectively. Three examiners performed manual measurements of the FAZ, and interrater and intrarater reliability were obtained.

RESULTS

The intraclass correlation coefficient (ICC) for interrater reliability for individual measurements was 0.62 (moderate) with a 95% confidence interval (CI) of 0.40 to 0.79 (p < 0.001). The ICC (95% CI) for intrarater reliability was 0.92 (0.82 to 0.96) for rater A, 0.96 (0.91 to 0.98) for B, and 0.88 (0.76 to 0.94) for C (p < 0.001). In all subanalyses including presence of edema and type of occlusion, interrater reliability was poor/moderate, and intrarater reliability was good/excellent.

CONCLUSION

The FAZ varies significantly among eyes with RVO, so measurements obtained using OCTA should be analyzed with caution due to the moderate level of reliability among different examiners.

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

BACKGROUND

Optical coherence tomography angiography (OCTA) provides not only visualisation but also quantitative measurement of foveal avascular zone (FAZ). Media opacity is common in elderly subjects with cataracts. This study aimed to investigate the impact of media opacity on automated and manual FAZ measurement.

METHODS

Cirrus 5000 OCTA and Triton OCTA were used to image FAZ using a 3×3 mm scanning protocol from 30 eyes of 30 healthy normal subjects. Media opacity was simulated with neutral-density filters (optical density (OD): 0.10-0.48 in Cirrus 5000 and 0.15-0.51 in Triton). Signal strength (SS) and signal strength intensity (SSI) were provided by the built-in software in Cirrus 5000 and Triton, respectively. FAZ area, perimeter and circularity were measured automatically using the built-in software as well as a customised MATLAB program. FAZ metrics were also measured manually. The correlations between the OD, SS/SSI and FAZ metrics were analysed using Spearman correlation.

RESULTS

Increased OD significantly correlated with decreased SS/SSI (r_s =-0.602 and -0.925, respectively, both p<0.001), decreased automated FAZ area (r_s =-0.344 and -0.766, respectively, both p<0.001), but increased manual FAZ area in both Cirrus 5000 and Triton (r_s =0.423 and 0.543, respectively, both p<0.001). Similar results were found for FAZ perimeter and circularity. There was a positive correlation between SS/SSI with the automated FAZ area but negative correlation with the manual FAZ area.

CONCLUSIONS

The effect of media opacity on quantitative measurement of FAZ is different between automated and manual measurements. Cautions must be taken when interpreting FAZ measurement in eyes with media opacity.

Quantitative Analysis of Retinal Microvascular Changes after Conbercept Therapy in Branch Retinal Vein Occlusion Using Optical Coherence Tomography Angiography

PURPOSE

To quantitatively evaluate microvascular changes in eyes with macular oedema due to branch retinal vein occlusion (BRVO) using optical coherence tomography angiography (OCTA) before and after intravitreal conbercept injection and the correlation of such changes with best-corrected visual acuity (BCVA) and retinal thickness.

METHODS

Twenty-eight eyes of 28 patients treated with a single intravitreal injection of conbercept for macular oedema due to BRVO were included in this study. The automatically measured values of the vessel density in the superficial (SCP) and deep retinal capillary plexus (DCP), the foveal avascular zone (FAZ) area, the FAZ perimeter, the vessel density within a 300 μm wide ring surrounding the FAZ (FD-300), the acircularity index (AI), the choriocapillaris flow area and the retinal thickness were obtained via OCTA before and at 1 month after initial injection and compared with those of age- and sex- matched healthy subjects.

RESULTS

In BRVO eyes, the vascular density in the SCP and DCP, the FD-300 and the flow area of choriocapillaris were significantly lower than those in healthy eyes, while the AI and the retinal thickness were significantly increased. After treatment, the retinal thickness in eyes with BRVO was significantly decreased in all quadrants, and the mean BCVA dramatically increased from 20/162 to 20/78 (p = 0.0017). The mean flow area of choriocapillaris significantly improved after treatment. Moreover, negative correlations between the logMAR BCVA and the whole vascular density in the SCP and DCP as well as the flow area of choriocapillaris were observed.

CONCLUSION

OCTA enables non-invasive, layer-specific and quantitative assessment of microvascular changes in eyes with BRVO before and after treatment, and it can be used as a valuable imaging tool for the evaluation of the follow-up in BRVO patients.

Microvascular changes after conbercept therapy in central retinal vein occlusion analyzed by optical coherence tomography angiography

AIM

To investigate microvascular changes in eyes with central retinal vein occlusion (CRVO) complicated by macular edema before and after intravitreal conbercept injection and evaluate correlations between these changes and best-corrected visual acuity (BCVA) and retinal thickness.

METHODS

Twenty-eight eyes of 28 patients with macular edema caused by CRVO were included in this retrospective study. All patients received a single intravitreal conbercept injection to treat macular edema. BCVA and the results of optical coherence tomography angiography (OCTA) automatic measurements of the vessel density in the superficial (SCP) and deep retinal capillary plexus (DCP), the foveal avascular zone (FAZ) area, the FAZ perimeter (PERIM), the vessel density within a 300-µm wide ring surrounding the FAZ (FD-300), the acircularity index (AI), the choriocapillaris flow area, and retinal thickness were recorded before and at one month after treatment and compared with the results observed in age- and sex-matched healthy subjects.

RESULTS

The vessel density in the SCP and DCP, the FD-300, and the flow area of the choriocapillaris were all significantly lower in CRVO eyes than in healthy eyes, while the AI and retinal thickness were significantly higher (all P<0.05). After treatment, retinal thickness was significantly decreased, and the mean BCVA had markedly improved from 20/167 to 20/65 (P=0.0092). The flow area of the choriocapillaris was also significantly improved, which may result from the reduction of shadowing effect caused by the attenuation of macular edema. However, there were no significant changes in SCP and DCP vessel density after treatment. The flow area of the choriocapillaris at baseline was negatively correlated with retinal thickness.

CONCLUSION

OCTA enables the non-invasive, layer-specific and quantitative assessment of microvascular changes both before and after treatment, and can therefore be used as a valuable imaging tool for the evaluation of the follow-up in CRVO patients.

Impact of Baseline Retinal Nonperfusion and Macular Retinal Capillary Nonperfusion on Outcomes in the COPERNICUS and GALILEO Studies

PURPOSE

To evaluate the impact of baseline retinal capillary nonperfusion (RNP) and macular retinal capillary nonperfusion (MNP) status on outcomes at week 24 (W24).

DESIGN

Post hoc analyses of 2 phase 3, randomized, double-masked, multicenter, sham-controlled studies.

PARTICIPANTS

Three hundred sixty-six patients with macular edema secondary to central retinal vein occlusion randomized in COPERNICUS and GALILEO.

METHODS

We randomized patients 3:2 to receive intravitreal aflibercept 2 mg every 4 weeks or sham injections until W24. RNP and MNP were assessed by a masked independent reading center.

MAIN OUTCOME MEASURES

Proportion of patients with 10 disc areas (DA) or more of RNP and any degree of MNP at W24, relative risks of 10 DA or more of RNP or any degree of MNP at W24 developing, change from baseline in best-corrected visual acuity (BCVA) and central retinal thickness (CRT) by baseline RNP and MNP status, and relationship between baseline RNP and MNP status.

RESULTS

At baseline, 24.6% of patients showed 10 DA or more of RNP and 72.6% showed MNP, regardless of baseline RNP status. At W24, the pooled proportions of patients in the intravitreal aflibercept and sham groups with 10 DA or more of RNP were 11.6% and 29.0%, respectively (P = 0.0001); the respective proportions with any degree of MNP were 61.2% and 79.5% (P = 0.0008). Relative risks and 95% confidence intervals for intravitreal aflibercept versus sham were 0.4 (0.25-0.62) for 10 DA or more of RNP and 0.8 (0.68-0.90) for MNP, indicating a lower risk for these outcomes with intravitreal aflibercept than with sham. Mean BCVA change was greater in intravitreal aflibercept- versus sham-treated eyes, with less than 10 DA and 10 DA or more of RNP at baseline (+17.5 vs. +0.8 letters and +18.3 vs. -4.1 letters, respectively) and with and without baseline MNP (+15.7 vs. +0.3 letters and +17.1 vs. +0.4 letters, respectively). Agreement between baseline RNP and MNP status was low (κ = 0.12). The proportions of patients with 1 or more ocular serious adverse event in the intravitreal aflibercept- and sham-treated groups, respectively, were 3.2% and 11.3%.

CONCLUSIONS

At W24, visual and anatomic improvements, including perfusion status, were greater in eyes treated with intravitreal aflibercept than in eyes treated with sham, regardless of baseline RNP or MNP status.

Optical Coherence Tomography Angiography in Eyes with Retinal Vein Occlusion

Optical coherence angiography (OCTA) is a noninvasive technique that has been introduced in recent years to detect ophthalmological pathology. The growing usage of OCTA to detect retinal abnormalities can be attributed to its advantages over the reference-standard fluorescein angiography (FA), although both of these techniques can be used in association. OCTA's advantages include its dye independency, its ability to produce depth-resolved images of retinal and choroidal vessels that yield images of different vascular layers of the retina, and the better delineation of the foveal avascular zone. OCTA's disadvantages include the lack of normalized patient data, artefactual projection issues, and its inability to detect low-flow lesions or pathologic conditions. Different OCTA platforms use unique algorithms to detect microvasculature, which are implemented in both spectral-domain (SD) and swept-source (SS) OCT machines. Microvascular changes in retinal vein occlusions (RVOs) are visible in both the superficial and deep capillary networks of the retina in OCTA. These visualizations include a decrease in foveal and parafoveal vascular densities, non-perfusion areas, capillary engorgement and telangiectasias, vascular tortuosity, microaneurysms, disruption of the foveal perivascular plexus, and formation of collateral vessels. The restricted field of view and inability to show leakage are important limitations associated with the use of OCTA in RVO cases. In this article, we present a brief overview of OCTA and a review of the changes detectable in different slabs by OCTA in RVO cases published in PubMed and Embase.

Clinical applications of optical coherence tomography angiography: What we have learnt in the first 3 years

A review of the literature from 2014 to 2016 was conducted, focusing on the results of optical coherence tomography angiography in different chorioretinal diseases. In only 3 years, optical coherence tomography angiography has been shown to be an effective tool for diagnosing choroidal neovascularization complicating age-related macular degeneration, pathologic myopia, and inflammatory conditions. The technique has sometimes been considered superior to conventional multimodal imaging, for example, in choroidal neovascularization associated with chronic central serous chorioretinopathy or multifocal choroiditis. In retinal vascular diseases, optical coherence tomography angiography has helped to understand the condition described as paracentral acute middle maculopathy and has been considered highly effective for the analysis of retinal vascular macular changes secondary to retinal vein occlusion or macular telangiectasia. Changes in the foveal avascular zone, also reported in diabetic maculopathy, have been shown to occur before any angiographic signs. A reduction in capillary vascular density has been reported in the fovea of eyes with malignant melanoma, but not in eyes with choroidal nevus. However, optical coherence tomography angiography is a recent technique that probably needs refinements and further studies. Nevertheless, the first 3 years of optical coherence tomography angiography use suggest its clinical relevance and useful applications in daily clinical practice.

Optical coherence tomography angiography

Optical coherence tomography (OCT) was one of the biggest advances in ophthalmic imaging. Building on that platform, OCT angiography (OCTA) provides depth resolved images of blood flow in the retina and choroid with levels of detail far exceeding that obtained with older forms of imaging. This new modality is challenging because of the need for new equipment and processing techniques, current limitations of imaging capability, and rapid advancements in both imaging and in our understanding of the imaging and applicable pathophysiology of the retina and choroid. These factors lead to a steep learning curve, even for those with a working understanding dye-based ocular angiography. All for a method of imaging that is a little more than 10 years old. This review begins with a historical account of the development of OCTA, and the methods used in OCTA, including signal processing, image generation, and display techniques. This forms the basis to understand what OCTA images show as well as how image artifacts arise. The anatomy and imaging of specific vascular layers of the eye are reviewed. The integration of OCTA in multimodal imaging in the evaluation of retinal vascular occlusive diseases, diabetic retinopathy, uveitis, inherited diseases, age-related macular degeneration, and disorders of the optic nerve is presented. OCTA is an exciting, disruptive technology. Its use is rapidly expanding in clinical practice as well as for research into the pathophysiology of diseases of the posterior pole.

DualTrack Technology Improves Optical Coherence Tomography Angiography Image Quality

BACKGROUND AND OBJECTIVE

To evaluate the effects of DualTrack Motion Correction Technology on the performance of AngioVue optical coherence tomography angiography (Optovue, Freemont, CA).

PATIENTS AND METHODS

Fifty subjects underwent two consecutive examinations with AngioVue. The operator inactivated the eye-tracking (ET) technology before the second examination. Two operators measured execution time, excluded low-quality images, and counted the number of motion artifacts per image.

RESULTS

The mean execution time was lower without ET in all the groups (P < .05), regardless of retinal diseases. Percentages of available images and low-quality images were 75.0% and 25.0%, respectively, with ET and 63.0% and 37.0%, respectively, without ET. Mean number of motion artifacts was significantly lower in images obtained using ET compared to images obtained without ET in all the groups (P < .0001), regardless of retinal diseases.

CONCLUSION

Although ET technology increases the mean execution time, the reduction of motion artifacts and the increase of high-quality images may represent a great advantage in clinical practice. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:918-926.].

Optical Coherence Tomography Angiography to Estimate Retinal Blood Flow in Eyes with Retinitis Pigmentosa

Ophthalmologists sometimes face difficulties in identifying the origin of visual acuity (VA) loss in a retinitis pigmentosa (RP) patient, particularly before cataract surgery: cataract or the retinal disease state. Therefore, it is important to identify the significant factors correlating with VA. Nowadays, retinal blood flow in superficial and deep layers can be estimated non-invasively using optical coherence tomography angiography (OCTA). We estimated blood flow per retinal layer by using OCTA; investigated the correlation between VA and other parameters including blood flow and retinal thickness; and identified the most associated factor with VA in patients with RP. OCTA images in 68 of consecutive 110 Japanese RP patients were analysable (analysable RP group). Thirty-two age- and axial length-matched healthy eyes (control group) were studied. In the analysable RP group, the parafoveal flow density in superficial and deep layers was 47.0 ± 4.9% and 52.4 ± 5.5%, respectively, which was significantly lower than that in controls. Using multivariate analysis, we found that the parafoveal flow density in the deep layer and superficial foveal avascular area were the factors associated with VA. Non-invasive estimation of retinal blood flow per retinal layer using OCTA is useful for predicting VA in RP patients.