Dense B-Scan Optical Coherence Tomography Angiography

Digital histology of retinal microaneurysms as provided by dense B-scan (DART) OCTA: characteristics and clinical relevance in diabetic retinopathy

BACKGROUND

Retinal microaneurysms (MAs) are among the earliest signs of diabetic retinopathy (DR) and can be classified in several subtypes by non-invasive multimodal retinal imaging. The main aim of the present study is to characterize retinal MAs perfusion properties and their blood flow network connectivity by means of Dense Automatic-RealTime (DART) OCTA technology, checking the relationship with the multimodal retinal imaging classification and testing the clinical impact of DART.

METHODS

A cross-sectional, observational study setting was chosen. Multimodal retinal imaging included confocal multicolour, OCT, OCTA and DART OCTA. We classified retinal MAs accordingly with the recently proposed multimodal retinal imaging classification and we tested the role of DART OCTA for detecting retinal MAs blood flow network connectivity. We also tested the relationship with clinical parameters.

RESULTS

We included 206 retinal MAs of 36 DR eyes. We categorized retinal MAs as red (70; 34%), mixed (106; 51%) and green (30; 15%), corresponding to precise characteristics on structural OCT and both (regular) enface and DART OCTA images. The agreement between en-face and DART OCTA techniques for detecting MAs perfusion was very high (overall ICC 0.98; p < 0.01). However, DART OCTA provided clearer visualization than enface OCTA for detecting the blood flow network connectivity of retinal MAs, especially looking at the afferent and efferent MAs capillaries. Multimodal retinal imaging classification of retinal MAs provided significant correlations with DR duration, DR stage, and macular capillary non-perfusion.

CONCLUSIONS

DART OCTA provided several new insights on retinal MAs characteristics and their blood flow network connectivity.

Quantitative analysis of peripapillary capillary volume using dense B-scan OCT angiography in normal and diabetic retina

BACKGROUND

The value of quantitatively analyzing peripapillary capillary volume (PPCV) distribution was explored in normal and diabetic retinopathy (DR) eyes using dense B-scan optical coherence tomography angiography (DB OCTA).

METHODS

This was a cross-sectional observational study followed by prospective follow-up for those with DR, which enrolled 101 healthy subjects and 140 DR patients. Dense, automatic, real-time (DART) volume scans of DB OCTA were performed using a Spectralis HRA + OCT2. ImageJ and MATLAB were used to process and calculate PPCV distribution detected by DB OCTA.

RESULTS

In normal subjects, PPCV distribution were significantly correlated with the age and quadrant location (all P < 0.001). The PPCV distribution in each quadrant was significantly lower in severe nonproliferative DR patients than in normal subjects in all age groups (all P < 0.05, t-test). Compared to normal subjects, the PPCV distribution improved significantly in the pan-retinal photocoagulation treatment and surgery groups (all P < 0.001). No significant variation was observed in the anti-VEGF treatment group and normal subjects (P > 0.05). The PPCV distribution is significantly correlated with post-treatment best-corrected visual acuity in both the pan-retinal photocoagulation treatment and surgery groups (all P < 0.003) but not in the anti-VEGF treatment group (P = 0.940).

CONCLUSIONS

Quantitative assessment of PPCV distribution using DB OCTA is valuable in prognosis evaluation of DR with pan-retinal photocoagulation and surgery.

Optical coherence tomography angiography biomarkers in a bi-monthly maintenance dosing aflibercept in patients with neovascular age-related macular degeneration

PURPOSE

To evaluate the correlations between swept-source optical coherence tomography angiography (SS-OCTA) parameters and clinical outcomes in eyes with neovascular age-related macular degeneration (nAMD) administered a bimonthly intravitreal aflibercept regimen.

METHODS

This prospective, single-arm, interventional study enrolled 33 patients with treatment-naïve nAMD. The eyes received three monthly aflibercept injections followed by five bi-monthly regimens (total 50 weeks). The structural parameters including central subfield thickness (CST) and 5 mm pigment epithelial detachment (PED) volume and microvascular parameters including macular neovascularization (MNV) area, vessel density (VD), and vessel length density (VLD) were recorded every before and 1 week after treatment.

RESULTS

Patients who gained > 5 letters of best-corrected visual acuity (BCVA) from the baseline showed greater decreases in VD and VLD during the loading phase. Patients without recurrent or persistent fluid during the maintenance phase showed greater decreases in CST and 5 mm PED volume after the first injection. The decrease in mean VD during the loading phase was significantly correlated with the final BCVA (r = -0.820, p = 0.004). Moreover, the decrease in mean VLD during the loading phase was significantly correlated with the improvement in the final BCVA (r = -0.726, p = 0.017).

CONCLUSIONS

The decrease in mean VD during the loading phase was significantly negatively correlated with the final BCVA at the last visit. The decrease in mean VLD during the loading phase, mean CST during the loading phase, and the improvement in final BCVA showed significant correlations. Therefore, early changes in OCTA microvascular and OCT structural parameters could help predict clinical outcomes in nAMD.

TRIAL REGISTRATION

The trial was registered with the Clinical Research Information Service (CRIS), which joined the WHO International Clinical Trials Registry Platform (ICTRP) (Registration number: KCT0007375, Date of first trial registration: 10/06/2022).

The Development and Clinical Application of Innovative Optical Ophthalmic Imaging Techniques

The field of ophthalmic imaging has grown substantially over the last years. Massive improvements in image processing and computer hardware have allowed the emergence of multiple imaging techniques of the eye that can transform patient care. The purpose of this review is to describe the most recent advances in eye imaging and explain how new technologies and imaging methods can be utilized in a clinical setting. The introduction of optical coherence tomography (OCT) was a revolution in eye imaging and has since become the standard of care for a plethora of conditions. Its most recent iterations, OCT angiography, and visible light OCT, as well as imaging modalities, such as fluorescent lifetime imaging ophthalmoscopy, would allow a more thorough evaluation of patients and provide additional information on disease processes. Toward that goal, the application of adaptive optics (AO) and full-field scanning to a variety of eye imaging techniques has further allowed the histologic study of single cells in the retina and anterior segment. Toward the goal of remote eye care and more accessible eye imaging, methods such as handheld OCT devices and imaging through smartphones, have emerged. Finally, incorporating artificial intelligence (AI) in eye images has the potential to become a new milestone for eye imaging while also contributing in social aspects of eye care.

EVALUATION OF SEGMENTAL RETINAL ARTERITIS WITH OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PURPOSE

To describe the vascular anatomy and intraluminal flow characteristics of segmental retinal arteritis (SRA) using structural and angiographic optical coherence tomography (OCT).

METHODS

Retrospective case series of consecutive patients presenting with SRA. All patients were evaluated at presentation with fundus photography, spectral domain OCT, and OCT angiography. One patient was imaged with dense B-scan OCT angiography.

RESULTS

Three eyes of three male patients were evaluated. All examinations were consistent with reactivation of ocular toxoplasmosis with an area of active retinochoroiditis adjacent to a focal chorioretinal scar. Spectral domain OCT through areas of SRA noted on clinical examination demonstrated areas of hyperreflectivity circumscribing the affected vessel with a normoreflective lumen. Optical coherence tomography angiography and dense B-scan OCT angiography demonstrated narrowing of the intraluminal flow signal that correlated with areas of segmental hyperreflectivity on spectral domain OCT. Vascular sections proximal and distal to areas of SRA showed normal flow signal.

CONCLUSION

Vessels with SRA demonstrated hyperreflectivity highlighting the vessel wall on spectral domain OCT. Optical coherence tomography angiography showed narrowing of the flow signal within these segments suggesting reduced lumen diameter. Coupling these finding with previous indocyanine green imaging findings in SRA, the collective data suggest the plaques are localized within the vessel wall to either the endothelium or the muscular tunica media without occlusion of the vessel lumen.

Multimodal Imaging of Laser-Induced Retinal-Choroidal Anastomosis Masquerading as Type 3 Macular Neovascularization

The use of laser to induce a retinal-choroidal anastomosis (RCA) through photomechanical and photothermal rupture of the retinal pigment epithelium/Bruch's membrane beneath a retinal vein has been performed in eyes with retinal vein occlusion to create an alternate pathway for retinal venous outflow. The authors document the multimodal imaging findings of a 64-year-old female with type 2 diabetes presenting with a parafoveal vascular lesion simulating type 3 macular neovascularization. A review of the medical history and the benign course of the lesion suggested its inadvertent origin from prior focal/grid laser to treat diabetic macular edema. [Ophthalmic Surg Lasers Imaging Retina. 2020;51:244-248.].

Radial Peripapillary Capillary Plexus Sparing and Underlying Retinal Vascular Impairment in Intermediate Age-Related Macular Degeneration

Purpose

To examine location-specific retinal vascular changes in intermediate age-related macular degeneration (iAMD) using age-matched, high-density en face optical coherence tomography angiography (OCTA) cluster analysis.

Methods

En face OCTA images of the 6 × 6 mm macular area were retrospectively acquired from 60 iAMD eyes and 60 age-matched normal eyes and then subdivided into 126 × 126 (47.62 × 47.62 µm) grids within the superficial and deep vascular complex. Grid-wise vessel perfusion (VP) were compared between iAMD and normal eyes from the corresponding 10-yearly age cohort, forming difference plots. Difference plots were further separated by normative topographical map spatial clusters (C_1-6), derived from normal_database eyes (n = 236, 20–81 years old).

Results

Overall difference plots showed decreased VP in the superficial (−12.19%) and deep vascular complex (−6.44%) of iAMD compared to normal eyes (P < 0.0001 both comparisons). Cluster-based difference plots highlighted nonuniform changes in the superficial vascular complex, with sparing of VP at the nasal macula (corresponding to the radial peripapillary capillary plexus) versus decreased VP toward the temporal macula and foveal avascular zone (FAZ) (C_1–6 all comparisons P < 0.0001, except C₁ vs. C₂P > 0.99 and C₄ vs. C₅P = 0.11). The deep vascular complex displayed diffusely decreased VP, greater at the FAZ (P < 0.0001).

Conclusions

High-density en face OCTA cluster analysis suggests relative sparing of the radial peripapillary capillary plexus and impairment of underlying retinal vasculature, supporting potential anterograde transsynaptic degeneration in iAMD. These location-specific data may better guide future diagnostic and management protocol of iAMD.

Volume Rendering of Dense B-Scan Optical Coherence Tomography Angiography to Evaluate the Connectivity of Macular Blood Flow

Purpose

To characterize macular blood flow connectivity using volume rendering of dense B-scan (DB) optical coherence tomography angiography (OCTA) data.

Methods

This was a prospective, cross-sectional, observational study. DB OCTA perifoveal scans were performed on healthy subjects using the Spectralis HRA+OCT2. A volumetric projection artifact removal algorithm and customized filters were applied to raw OCTA voxel data. Volume rendering was performed using a workflow on Imaris 9.5 software. Vascular graphs were obtained from angiographic data using the algorithm threshold-loops. Superficial arteries and veins were identified from color fundus photographs and connections between adjacent arteries and veins displayed using the shortest path algorithm. Connective pathway locations were analyzed with cross-sectional OCT and OCTA to determine their course through the superficial vascular complex (SVC) and the deep vascular complex (DVC).

Results

Fourteen eyes from seven subjects (mean age: 28 ± 5 years; 3 women) were included in this analysis. One hundred and twenty-six vascular connections were analyzed. In all cases, the shortest path connections between superficial arteries and veins coursed through the DVC. We did not identify shortest path connections confined to the SVC.

Conclusions

Volumetric analysis of vascular connectivity supports a predominantly in-series arrangement of blood flow between the SVC and DVC within the human perifoveal macula.

Exudative non-neovascular age-related macular degeneration

PURPOSE

To describe the clinical and multimodal imaging (MMI) features of age-related macular degeneration (AMD) eyes presenting with intraretinal exudation and no evidence of neovascularization or structural alterations of native retinal vessels.

METHODS

This was a retrospective review of the MMI and electronic health records for 3 consecutive patients presenting with unilateral exudative non-neovascular age-related macular degeneration. MMI included confocal color fundus photography (CFP), fundus autofluorescence (FAF), fluorescein angiography (FA), spectral domain optical coherence tomography (SD-OCT), swept-source optical coherence tomography angiography (SS-OCTA), and spectral domain optical coherence tomography angiography (SD-OCTA). Dense B-scan OCTA (DB-OCTA) patterns and implemented image post-processing were used to improve spatial resolution in the OCTA analysis and remove projection artifacts.

RESULTS

Three eyes of 3 patients (1 male and 2 females, ages 72-87) developed intraretinal fluid (IRF) producing retinal edema during regular follow-up for non-neovascular AMD. FA, SS-OCTA, and DB-OCTA demonstrated no evidence of macular neovascularization or discrete retinal vascular abnormalities that could explain the IRF accumulation. Two eyes received intravitreal anti-VEGF therapy and demonstrated prompt resolution of IRF with periodic recurrences over time.

CONCLUSION

Exudative non-neovascular AMD is a novel clinical phenotype characterized by the presence of non-neovascular intraretinal exudation producing macular edema. Differentiating this condition from other manifestations of AMD requires appropriate use of MMI. Further study is needed to assess the clinical impact and optimal management of exudative non-neovascular AMD.

Comparison and Repeatability of High Resolution and High Speed Scans from Spectralis Optical Coherence Tomography Angiography

Purpose

The purpose of this study was to evaluate and compare the repeatability of optical coherence tomography angiography (OCTA) derived retinal vascular quantitative metrics using high resolution (HR) versus high speed (HS) acquisition modes.

Methods

Macular 4.4 × 2.9-mm OCTA images from normal, healthy volunteers were captured using both HR (768 A-scans × 256 B-scans) and HS (384 A-scans × 256 B-scans) acquisition protocols. Vessel density and vessel length density of the superficial capillary plexus and deep capillary plexus, as well as choriocapillaris flow deficit were computed. In a subset of eyes, the OCTA scans were repeated twice 2 days later and the same metrics were recomputed to assess repeatability, using intraclass correlation coefficients and coefficient of variation (CV).

Results

Comparison of measurements between HR and HS acquisitions in 41 healthy eyes showed statistically significant differences for all quantitative metrics (P < 0.01). However, no significant differences were observed among the three repeated scans (one on day 1 and two on day 3) obtained with each of the acquisition modes. The CVs ranged from 0.01 to 0.03 with the HR mode and 0.01 to 0.04 with the HS mode. The intraclass correlation coefficients (ICCs) among measurements were similar and high for both HR and HS modes, ranging from 0.844 to 0.949.

Conclusions

HR and HS OCTA acquisition modes both yielded repeatable quantitative metrics for the retinal circulation and the choriocapillaris. However, despite a similar field, the HR and HS derived measurements differed significantly.

Translational Relevance

To establish OCTA imaging in clinical and research practice, standardized and repeatability image analysis are necessary.

Linear and planar reflection artifacts on swept-source and spectral-domain optical coherence tomography due to hyperreflective crystalline deposits

PURPOSE

To describe novel spectral-domain (SD) and swept-source (SS) optical coherence tomography (OCT) linear and planar reflection artifacts produced by hyperreflective crystalline deposits (HCD).

METHODS

Imaging from 10 eyes with HCD producing linear and planar artifacts on OCT was retrospectively analyzed. All eyes had SD-OCT (Spectralis HRA + OCT, Heidelberg Engineering, Germany) and SS-OCT angiography (PLEX Elite 9000, Carl Zeiss Meditec, Inc., Dublin, CA) acquired on the same day. The horizontal extent of planar artifacts and the corresponding HCD on B-scans was measured using a digital caliper. Artifact features from HCD in eyes with non-neovascular age-related macular degeneration (AMD) were analyzed and compared to those seen in two eyes with the "onion sign," an OCT signature previously shown to represent cholesterol crystals (CC) in the sub-retinal pigment epithelium-basal laminar space of eyes with neovascular AMD. A third eye with the "onion sign" was imaged with dense B-scan (DB)-OCTA.

RESULTS

Ten eyes of ten patients (77.4 ± 8.7 years) with HCD were analyzed. On SS-OCTA, HCD produced linear artifacts of high signal intensity passing through the HCD and spanning the entire scan depth. On SD-OCT, HCD produced planar artifacts located anterior to both the retina and a hyporeflective space representing normal vitreous signal. The horizontal extent of the artifact did not differ significantly from the corresponding HCD on OCT B-scans (P = 0.62). The OCT artifacts produced by the "onion sign" appeared similar to those of HCD. The additional eye with neovascular AMD imaged with DB-OCTA was characterized by a single, vertical, linear false-flow signal crossing retinal layers.

CONCLUSIONS

To the authors' knowledge, this is the first description of SD- and SS-OCT/OCTA artifacts corresponding to both HCD and the "onion sign." These artifacts are likely due to highly reflective CC previously shown on histology to correspond to both of these OCT signatures.

Association of Optical Coherence Tomography Angiography of Collaterals in Retinal Vein Occlusion With Major Venous Outflow Through the Deep Vascular Complex

Importance

Analysis of collateral vessel formation following retinal vein occlusion may advance our understanding of the venous outflow anatomy in the macula.

Objective

To determine the location of collateral vessels with optical coherence tomography (OCT) angiography imaging.

Design, Setting, and Participants

Observational retrospective cohort study. Collateral vessel formation was studied with OCT angiography (OCTA) in patients with retinal vein occlusion (RVO). The study took place at 2 retinal practices (Vitreous Retina Macula Consultants of New York and Stein Eye Institute, University of California, Los Angeles), with patient records retrieved from March 2015 to August 2017. Data analysis was completed in November 2017.

Exposures

Collaterals identified with fundus photography and/or fluorescein angiography were analyzed with OCTA to determine their course through the superficial vascular plexus (SVP) and the deep vascular complex (DVC).

Main Outcomes and Measures

Collateral vessel pathways through the SVP and DVC were analyzed with cross-sectional and en face OCT and OCTA segmentation and color-coded volume renderings prepared from raw OCTA voxel data.

Results

From 23 eyes (22 branch and 1 hemispheric retinal vein occlusion ) of 23 patients (mean [SD] age, 73 [11] years), 101 collateral vessels were identified and analyzed (mean [SD], 4.4 [2.0]; range, 2-9 collateral per eye). On OCTA, the collaterals appeared as curvilinear dilated flow signals that connected veins across the horizontal raphe or veins on opposite sides of an occluded venous segment within the same retinal hemisphere. Of the 101 collaterals analyzed, all showed greater flow signal in the DVC, and all had some portion of their course identified within the DVC. No collaterals were found exclusively in the SVP. Volume renderings for 3 cases confirmed qualitatively that retinal collateral vessels course through the retina predominantly at the level of the DVC.

Conclusions and Relevance

Based on a limited number of cases, all collateral vessels associated with retinal vein occlusion were found to course through the DVC. The absence of collaterals isolated to the SVP supports a serial arrangement of the SVP and DVC, with venous drainage predominantly coursing through the DVC.