Imaging choroidal neovascular membrane using en face swept-source optical coherence tomography angiography

Quantitative analysis of choroidal vascular structures and anatomical changes in pachychoroid spectrum diseases using ultra-widefield SS-OCTA

This study used ultra-widefield swept-source optical coherence tomography angiography (UWF SS-OCTA) to analyze and compare choroidal blood flow and anatomical changes in eyes affected by central serous chorioretinopathy (CSC), pachychoroid neovasculopathy (PNV), and uncomplicated pachychoroid (UCP). The findings revealed distribution patterns of vortex veins across the three patient groups and provided initial findings insights into the origin of choroidal neovascularization (CNV) in PNV. A total of 44 patients with CSC, 38 with PNV, and 46 with UCP were included in the analysis. Three-dimensional data were obtained from scans measuring 20 mm vertically by 24 mm horizontally with a scan depth of 6 mm, covering nine subfields. The results showed that CSC groups exhibited significantly higher choroidal vessel volume per unit area (mCVV/a), choroidal vascularity index (CVI), and choroidal thickness (CT) compared to the PNV and UCP groups. While the PNV and UCP groups shared similar choroidal vascular characteristics, the PNV group exhibited slightly higher choroidal vessel volume and notably the lowest foveal choriocapillaris density. These findings suggest that PNV and CSC may represent a continuous pathological spectrum, while UCP might be considered a precursor to CSC or a stage following its resolution. Additionally, further analysis indicated that CNV in PNV could be attributed to choriocapillaris occlusion and ischemia resulting from mechanical compression by hypertrophic choroidal vessels. These findings enhance our understanding of choroidal structure and hemodynamics within pachychoroid spectrum diseases (PSD), shedding light on shared etiological mechanisms and advancing the characterization of their pathophysiology.

Correlation of the OCT Double-Layer Sign with Type 1 Non-Exudative Neovascularization on OCT-A in Age-Related Macular Degeneration

Background and Objectives: Early diagnosis of the exudative form of age-related macular degeneration (AMD) is very important for a timely first treatment, which is directly related to the preservation of functional visual acuity over a long period. The goal of this paper was to examine the correlation between the double-layer sign (DLS) and the presence of non-exudative macular neovascularization (MNV). Materials and Methods: Our research included 60 patients with AMD, exudative in one eye and non-exudative in the other eye. We analyzed only the non-exudative form using optical coherence tomography (OCT) and optical coherence tomography angiography (OCT-A). The patients were classified into three groups, depending on the duration of the disease (<2 years, 2 to 5 years, >5 years). The onset of the disease was deemed the moment of establishing a diagnosis of exudative AMD in one eye. We defined the presence or absence of a DLS using OCT and the presence of non-exudative MNV using OCT-A, both on 3 × 3 mm and 6 × 6 mm sections. DLS was used as a projection biomarker for non-exudative MNV, with the aim of establishing a rapid diagnosis and achieving early treatment of the disease. Results: We found that there was a statistically significant correlation between the DLS diagnosed using OCT and non-exudative MNV diagnosed by OCT-A for both 3 × 3 mm (p < 0.001) and 6 × 6 mm (p < 0.001) imaging. There was a statistically significant difference between the frequencies of both DLS and MNV in Groups I and III on both 3 × 3 and 6 × 6 mm imaging. A statistically significant difference was also noted in the frequencies of DLS and MNV on 6 × 6 mm imaging, but not on 3 × 3 mm imaging, between Groups I and II. No differences were found between the frequencies of DLS and MNV between Groups II and III. Conclusions: The DLS on OCT can be used as a projection biomarker to assess the presence of a non-exudative MNV.

Persistent reduction of retinal microvascular vessel density in patients with moderate and severe COVID-19 disease

OBJECTIVE

This study aims to analyse the possible recovery or worsening in retinal microvasculature after 8 months in a previously studied COVID-19 cohort.

METHODS AND ANALYSIS

A cross-sectional case-control study and a prospective longitudinal cohort study. Participants were the subjects of our previous study who re-enrolled for a new examination including a fundus photograph (retinography), an optical coherence tomography (OCT) scan and an OCT angiography. COVID-19 diagnosed patients were divided into three groups: group 1: mild disease, asymptomatic/paucisymptomatic subjects who received outpatient care; group 2: moderate disease and group 3: severe disease, both of which required hospital admission because of pneumonia. Statistical analyses were performed using SPSS software (V.23.0). Cross-sectional intergroup differences were analysed by means of analysis of variance for normally distributed variables and the Kruskal-Wallis test for non-normally distributed ones. In reference to the prospective part of the study (intragroup differences, baseline with 8-month comparison), a paired t-test was used for normally distributed data and Wilcoxon signed ranks sum for non-normally distributed data.

RESULTS

The fovea-centered superficial and deep vascular densities were significantly diminished in severe cases compared with mild cases (p=0.004; p=0.003, respectively, for superficial and deep) and to controls (p=0.014; p=0.010), also in moderate cases to mild group (p=0.004; p=0.003) and to controls (p=0.012; p=0.024). In the longitudinal study, no significant statistical differences were found between baseline and 8-month follow-up vessel density values.

CONCLUSION

We demonstrated persistent reduction in the central vascular area over time in patients with moderate and severe COVID-19.

Contrast enhancement and speckle suppression in OCT images based on a selective weighted variational enhancement model and an SP-FOOPDE algorithm

Simultaneous contrast enhancement and speckle suppression in optical coherence tomography (OCT) are of great significance to medical diagnosis. In this paper, we propose a selective weighted variational enhancement (SWVE) model to enhance the structural parts of OCT images, and then present a shape-preserving fourth-order-oriented partial differential equations (SP-FOOPDE) algorithm to suppress speckle noise. To be specific, in the SWVE model, we first introduce the fast and robust fuzzy c-means clustering (FRFCM) algorithm to generate masks based on the gray-level histograms of the reconstructed OCT images and utilize the masks to distinguish the structural parts from the background. Then the retinex-based weighted variational model, combined with gamma correction, is adopted to enhance the structural parts by multiplying the estimated reflectance with the adjusted illumination. In the despeckling process, we present an SP-FOOPDE algorithm with the fidelity term modified by the shearlet transform to strike a splendid balance between noise suppression and structural preservation. Experimental results show that the proposed method performs well in contrast enhancement and speckle suppression, with better quality metrics of the MSE, PSNR, CNR, ENL, EKI, and ν and better noise immunity than the related method. Moreover, the application to the segmentation preprocessing exhibits that the retinal structure of the OCT images processed by the proposed method can be completely segmented.

Optical coherence tomography angiography for identifying choroidal neovascular membranes: a masked study in clinical practice

BACKGROUND/OBJECTIVES

Optical coherence tomography angiography (OCT-A) allows non-invasive imaging of chorio-retinal vasculature, and is a potential alternative to fluorescein angiography (FA). Sensitivity and specificity of OCT-A for detecting choroidal neovascularisation (CNV) in treatment-naïve neovascular age-related macular degeneration (nAMD) patients is examined, using the Heidelberg Spectralis in a 'real world' setting.

SUBJECT/METHODS

Overall, 43 eyes from 26 patients were included in the study. Spectral domain OCT (SD-OCT), OCT-A and FA images were obtained at baseline. Each of the three retinal image modalities was systematically assessed by three masked clinicians. Decisions about the presence/absence of CNV were recorded using an automated segmentation for OCT-A, a manual method, and using both OCT-A and SD-OCT in conjunction. Additional information about the presence of sub-retinal hyper-reflective material (SHRM) and the 'double layer sign' (DLS) were recorded.

RESULTS

The average sensitivity and specificity of the OCT-A for the detection of CNV in treatment naïve AMD was 89% and 87% for the combined SD-OCT and OCT-A, 76% and 91% for the automated segmentation and 84% and 85% for the manual segmentation, respectively. Inter-clinician agreement was 0.59-65 kappa. In patients without CNV, SHRM was present in only 6% while DLS was present in 28%. Sensitivity and specificity was >78% for both SHRM and DLS.

CONCLUSIONS

OCT-A provides a reliable tool for detecting CNV in treatment naïve nAMD patients, with high sensitivity and specificity. Combined use of SD-OCT images and SHRM as an additional bio-marker, OCT-A could become an alternative to FA in routine clinical practice.

Determination of peripapillary vessel density in optic disc drusen using EDI-OCT and OCT angiography

Optical coherence tomography angiography (OCTA) is a rapidly developing technique which generates angiographic images non-invasively. This study proposes a method to determine the vessel density in OCTA scans in general and especially the local peripapillary vessel density. The method produces vessel density heatmaps that contain information about the local vessel density. We apply the method in a small study to demonstrate its applicability and its potential to investigate the influence of local conditions on the vessel density. In the study, we combine information from enhanced depth imaging optical coherence tomography (EDI-OCT) about the location of optic disc drusen (ODD) with information from OCTA about the vessel density. We see a reduction in local peripapillary vessel density in peripapillary sections with a large volume of ODD.

Features and Diagnostic Accuracy of Optical Coherence Tomography Angiography in Neovascular Age-related Macular Degeneration

Introduction Age-related macular degeneration (AMD) is one of the important causes of visual impairment in aging population. Fundus fluorescein angiography (FFA) is gold standard for the diagnosis of neovascular AMD (nAMD) while optical coherence tomography (OCT) aids in the diagnosis of nAMD and is very useful for follow-up. OCT angiography (OCTA) is an evolving imaging technology that can be used as a valid diagnostic tool to study morphology of choroidal neovascularization (CNV) that is seen in nAMD. This study was conducted with the objective to determine diagnostic accuracy and OCTA features of occult and classic CNV in patients with nAMD. Methods In this prospective observational study, 90 eyes of 58 patients with nAMD were studied with OCT, OCTA and FFA. OCTA scans were analyzed to qualitatively describe the morphological appearance of CNV in terms of location, pattern and configuration. The OCTA sensitivity and specificity for CNV detection were calculated by comparing it with FFA. Results FFA detected CNV in 70 of the 90 eyes (77.77%) whereas OCTA identified CNV in 69 eyes (76.7%). Among 69 eyes with CNV, it was well-defined in 51 (73.9%) eyes and poorly defined in 18 (26.1%) eyes. There were four false positive and five false negative cases. The sensitivity, specificity, positive predictive value and negative predictive value of OCTA in detection of nAMD were found to be 92.85%, 80.0%, 94.2 and 76.2, respectively. Conclusion OCTA is a useful, noninvasive, reproducible imaging tool for diagnosing, classifying and localizing CNV. The technique has high sensitivity and specificity and can be used reliably in cases where FFA is contraindicated or inconclusive.

Advances in Retinal Optical Imaging

Retinal imaging has undergone a revolution in the past 50 years to allow for better understanding of the eye in health and disease. Significant improvements have occurred both in hardware such as lasers and optics in addition to software image analysis. Optical imaging modalities include optical coherence tomography (OCT), OCT angiography (OCTA), photoacoustic microscopy (PAM), scanning laser ophthalmoscopy (SLO), adaptive optics (AO), fundus autofluorescence (FAF), and molecular imaging (MI). These imaging modalities have enabled improved visualization of retinal pathophysiology and have had a substantial impact on basic and translational medical research. These improvements in technology have translated into early disease detection, more accurate diagnosis, and improved management of numerous chorioretinal diseases. This article summarizes recent advances and applications of retinal optical imaging techniques, discusses current clinical challenges, and predicts future directions in retinal optical imaging.