The Impact of Image Processing Algorithms on Optical Coherence Tomography Angiography Metrics and Study Conclusions in Diabetic Retinopathy

In vivo multi-contrast depth-resolved choroidal imaging of a mouse using polarization-diversity optical coherence tomography

The results of depth-resolved multi-contrast in vivo mouse choroidal imaging using a polarization-diversity optical coherence tomography (PD-OCT) system are presented. A selectively chosen depth of focus that was fine-tuned with a sensorless adaptive optics technique and a simple segmentation based on the degree of polarization uniformity signal visualizes the detailed features of a mouse choroid from the OCT angiography images. A comprehensive image analysis of the choroid revealed the distinctive pathological characteristics of the laser-induced choroidal neovascularization mouse.

Study of the impact of the vascular systemic risk factors on peripapillary vascular density by optical coherence tomography angiography

BACKGROUND

The focus of therapeutic tools in glaucoma has been mainly to control of intraocular pressure. Recently there has been a growing interest in investigating the relationship of vascular risk factors in the development of glaucoma. The aim of this study was to assess the association between systemic arterial hypertension, diabetes mellitus and hypercholesterolemia, and peripapillary vascularization measured by Optical Coherence Tomography Angiography (OCTA) in glaucoma and healthy subjects.

METHODS

In this unicenter, observational, cross-sectional study, 212 subjects, 118 glaucoma patients and 94 controls were consecutively recruited. Of these, 86 participants were excluded due to poor OCTA image quality. Therefore, 146 subjects were included in the final analysis, 74 glaucoma patients and 72 controls. Using a linear regression model, with 95% confidence and 80% statistical power, the effect of vascular risk factors on OCTA parameters in the 146 subjects included in the final analysis was studied.

RESULTS

No significant impact of vascular risk factors on OCTA measurements was found. Diabetic patients tended to show a lower peripapillary perfusion vascular density than subjects without diabetes (β 0.016, 95%CI 0.003;0.030, p 0.016). Similarly, hypercholesterolemia patients appeared to show less peripapillary flow index than non-hypercholesterolaemic patients (β 0.029, 95%CI 0.013;0.046, p 0.001). Glaucoma patients had 0.02% lower peripapillary perfusion vascular density (β 0.020, 95% CI 0.011;0.029, p < 0.001), 0.04% lower peripapillary flow index (β 0.036, 95%CI 0.022;0.051, p < 0.001) and 9.62% thinner retinal nerve fibre layer (β 9.619, 95%CI 5.495;13.744, p < 0.001).

CONCLUSIONS

In conclusion glaucoma has greater effect on peripapillary vascular density parameters than any of the vascular risk factors analyzed.

KEY MESSAGES

What is known: • Vascular disfunction plays an important role in the development of glaucoma. • Optical coherence tomography angiography makes it possible to assess the retinal microvasculature and the role that its alterations could have in the development of glaucoma.

WHAT IS NEW

• Decrease of the peripapillary microcirculation seems to be more related to the increase in intraocular pressure and the glaucoma itself than to the presence of cardiovascular risk factors. • The effect of having diabetes, systemic arterial hypertension or hypercholesterolaemia on vascular parameters or nerve fibre layer thickness was low. • There was also no relevant impact of the systemic medication used for these diseases on the peripapillary vascular parameters studied or on nerve fibre layer thickness.

Fractal Changes of the Retinal Microvasculature in Birdshot Chorioretinopathy

BACKGROUND AND OBJECTIVE

Retinal vascular disorders are associated with lower fractal dimension (FD). We analyzed FD in birdshot chorioretinopathy (BSCR).

PATIENTS AND METHODS

This was a retrospective cohort study. We performed optical coherence tomography angiography (OCTA) and analyzed FD of the superficial capillary plexus (SCP), deep capillary plexus (DCP), and choriocapillaris (CC) using ImageJ. For each vascular layer, we analyzed the presence of BSCR, subjects' age, sex, and presence of diabetes mellitus to determine which may predict lower FD.

RESULTS

We compared 28 eyes (14 patients) with BSCR to 34 control eyes (17 patients). Mean FD of BSCR was lower in SCP (1.584 [± 0.126] vs 1.706 [± 0.118], P < 0.001), DCP (1.637 [± 0.134] vs 1.780 [± 0.096], P < 0.001), and CC (1.884 [± 0.063] vs 1.917 [± 0.047], P = 0.036). FD of SCP was lower per increasing year (0.005 [P = 0.014]). Male patients had lower FD-DCP (0.101 [P = 0.043]).

CONCLUSION

In BSCR, fractal analysis showed significant involvement of the SCP, DCP, and to a lesser extent the CC. [Ophthalmic Surg Lasers Imaging Retina 2024;55:XX-XX.].

Association of Genetic Risk for Age-Related Macular Degeneration with Morphological Features of the Retinal Microvascular Network

BACKGROUND

Age-related macular degeneration (AMD) is a multifactorial disease encompassing a complex interaction between aging, environmental risk factors, and genetic susceptibility. The study aimed to determine whether there is a relationship between the polygenic risk score (PRS) in patients with AMD and the characteristics of the retinal vascular network visualized by optical coherence tomography angiography (OCTA).

METHODS

235 patients with AMD and 97 healthy controls were included. We used data from a previous AMD PRS study with the same group. The vascular features from different retina layers were compared between the control group and the patients with AMD. The association between features and PRS was then analyzed using univariate and multivariate approaches.

RESULTS

Significant differences between the control group and AMD patients were found in the vessel diameter distribution (variance: p = 0.0193, skewness: p = 0.0457) and fractal dimension distribution (mean: p = 0.0024, variance: p = 0.0123). Both univariate and multivariate analyses showed no direct and significant association between the characteristics of the vascular network and AMD PRS.

CONCLUSIONS

The vascular features of the retina do not constitute a biomarker of the risk of AMD. We have not identified a genotype-phenotype relationship, and the expression of AMD-related genes is perhaps not associated with the characteristics of the retinal vascular network.

Viral Anterior Uveitis: Differences in Retinal Vessel Area Density between the Affected and Non-Affected Eye Using Optical Coherence Tomography Angiography

PURPOSE

To investigate differences in the retinal vessel area density (VAD) on optical coherence tomography angiography (OCTA) between eyes with unilateral herpetic viral anterior uveitis (VAU) (herpes-simplex virus (HSV) and varicella-zoster virus (VZV)) and the non-affected fellow eye.

METHODS

In this monocentric, observational, prospective case series we analyzed the VAD of the macula, optic disc, and peripapillary region in affected and non-affected eyes of 22 patients with HSV-positive and 22 patients with VZV-positive VAU using OCTA. We analyzed also the visual field mean deviation (MD), the retinal nerve fiber layer (RNFL) thickness, Bruch's Membrane Opening-Minimum Rim Width (BMO-MRW), and ganglion cell layer (GCL) thickness on OCT and correlated the results with the different VADs.

RESULTS

The macular VAD in the superficial vascular plexus (SVC) was significant lower in the affected compared to the non-affected eye for both viruses (HSV: 33.0% ± 3.3% vs. 34.7% ± 2.6%, p = 0.011; adjusted p = 0.040; VZV: 33.1% ± 3.2% vs. 34.3% ± 2.8%, p = 0.012; adjusted p = 0.050). Additionally, the VAD of the peripapillary SVC differed between the affected and non-affected eye for VZV-positive VAU (47.1% ± 6.2% vs. 50.5% ± 6.3%, p = 0.048, adjusted p = 0.100). For both HSV-positive and VZV-positive VAU, there were correlations between macular or peripapillary SVC VAD and BMO-MRW, GCL thickness, RNFL thickness or MD of the affected eye.

CONCLUSION

We observed vascular dysfunction characterized by decreased macular and peripapillary VAD in the superficial plexus on OCTA in eyes with HSV- and VZV-positive VAU compared to non-affected fellow eyes. These changes might be an early sign of glaucomatous damage or may be a direct consequence of the herpes viruses themselves.

Comparison of Widefield OCT Angiography Features Between Severe Non-Proliferative and Proliferative Diabetic Retinopathy

INTRODUCTION

There is a high and ever-increasing global prevalence of diabetic retinopathy (DR) and invasive imaging techniques are often required to confirm the presence of proliferative disease. The aim of this study was to explore the images of a rapid and non-invasive technique, widefield optical coherence tomography angiography (OCT-A), to study differences between patients with severe non-proliferative and proliferative DR (PDR).

METHODS

We conducted an observational longitudinal study from November 2022 to March 2023. We recruited 75 patients who were classified into a proliferative group (28 patients) and severe non-proliferative group (47 patients). Classification was done by specialist clinicians who had full access to any multimodal imaging they required to be confident of their diagnosis, including fluorescein angiography. For all patients, we performed single-shot 4 × 4 and 10 × 10 mm (widefield) OCT-A imaging and when possible, the multiple images required for mosaic 17.5 × 17.5 mm (ultra widefield) OCT-A imaging. We assessed the frequency with which proliferative disease was identifiable solely from these OCT-A images and used custom-built MATLAB software to analyze the images and determine computerized metrics such as density and intensity of vessels, foveal avascular zone, and ischemic areas.

RESULTS

On clinically assessing the OCT-A 10 × 10 fields, we were only able to detect new vessels in 25% of known proliferative images. Using ultra-widefield mosaic images, however, we were able to detect new vessels in 100% of PDR patients. The image analysis metrics of 4 × 4 and 10 × 10 mm images did not show any significant differences between the two clinical groups. For mosaics, however, there were significant differences in the capillary density in patients with PDR compared to severe non-PDR (9.1% ± 1.9 in the PDR group versus 11.0% ± 1.9 for severe group). We also found with mosaics a significant difference in the metrics of ischemic areas; average area of ischemic zones (253,930.1 ± 108,636 for the proliferative group versus 149,104.2 ± 55,101.8 for the severe group.

CONCLUSIONS

Our study showed a high sensitivity for detecting PDR using only ultra-widefield mosaic OCT-A imaging, compared to multimodal including fluorescein angiography imaging. It also suggests that image analysis of aspects such as ischemia levels may be useful in identifying higher risk groups as a warning sign for future conversion to neovascularization.

Fractal Changes of the Retinal Microvasculature in Syphilitic Uveitis

PURPOSE

To quantify chorioretinal microvascular damage and recovery post-treatment in patients with acute syphilitic posterior placoid chorioretinitis (ASPPC) using fractal dimension (FD).

METHODS

Retrospective cohort study of patients with serologically confirmed syphilitic uveitis. We obtained optical coherence tomography angiography (OCTA) scans at baseline and follow-up after intravenous penicillin treatment and computed FD of the superficial capillary plexus (SCP), deep capillary plexus (DCP), and choriocapillaris (CC) using ImageJ.

RESULTS

We enrolled seven patients with ASPPC (11 eyes), and 17 control subjects (34 eyes). Pre-treatment averages of FD-SCP, FD-DCP, and FD-CC were: 1.672 (±0.115), 1.638 (±0.097), and 1.72 (±0.137); post-treatment: 1.760 (±0.071), 1.764 (±0.043), and 1.898 (±0.047). After treatment FD-CC increased in all 11 eyes with an average of 0.163 (p = 0.003); FD-DCP increased in 10 (91%) eyes with an average of 0.126 (p = 0.003); and FD-SCP increased in seven (64%) eyes with an average of 0.089 (p = 0.059). Compared to the post-treatment FD values in the syphilitic group, controls had similar FD-SCP (p = 0.266), FD-DCP (p = 0.078), and FD-CC (p = 0.449).

CONCLUSIONS

CC and DCP are mostly affected in ASPPC with minimal changes in the SCP. All vascular layers FD recovered after completing antibiotic treatment.

Application of ImageJ in Optical Coherence Tomography Angiography (OCT-A): A Literature Review

Background

This study aimed to review the literature on the application of ImageJ in optical coherence tomography angiography (OCT-A) images.

Methods

A general search was performed in PubMed, Google Scholar, and Scopus databases. The authors evaluated each of the selected articles in order to assess the implementation of ImageJ in OCT-A images.

Results

ImageJ can aid in reducing artifacts, enhancing image quality to increase the accuracy of the process and analysis, processing and analyzing images, generating comparable parameters such as the parameters that assess perfusion of the layers (vessel density (VD), skeletonized density (SD), and vessel length density (VLD)) and the parameters that evaluate the structure of the layers (fractal dimension (FD), vessel density index (VDI), and lacunarity (LAC)), and the foveal avascular zone (FAZ) that are used widely in the retinal and choroidal studies), and establishing diagnostic criteria. It can help to save time when the dataset is huge with numerous plugins and options for image processing and analysis with reliable results. Diverse studies implemented distinct binarization and thresholding techniques, resulting in disparate outcomes and incomparable parameters. Uniformity in methodology is required to acquire comparable data from studies employing diverse processing and analysis techniques that yield varied outcomes.

Conclusion

Researchers and professionals might benefit from using ImageJ because of how quickly and correctly it processes and analyzes images. It is highly adaptable and potent software, allowing users to evaluate images in a variety of ways. There exists a diverse range of methodologies for analyzing OCTA images through the utilization of ImageJ. However, it is imperative to establish a standardized strategy to ensure the reliability and consistency of the method for research purposes.

Cytomegalovirus-positive Posner-Schlossman syndrome: to compare differences in retinal vessel area density between the affected and non-affected eye using optical coherence tomography angiography

PURPOSE

To analyse differences in the retinal microvasculature in eyes with cytomegalovirus (CMV)-positive Posner-Schlossman syndrome (PSS) compared to the non-affected eyes using optical coherence tomography angiography (OCTA).

METHODS

In this monocentric, observational prospective case series, 25 patients with unilateral CMV-positive PSS were included. We compared the vessel area densities (VAD) in the macula, optic disc, and peripapillary region in PSS-affected and non-affected eyes using OCTA. We compared the visual fields (VF) of the affected and healthy eyes of each patient. The mean deviation (MD) of the VF was analysed together with the retinal nerve fibre layer (RNFL) thickness to evaluate the strength of correlation with the VAD parameters.

RESULTS

The VAD of the peripapillary superficial vascular complex (SVC) is significantly reduced in CMV-positive PSS-affected eyes (46.1 ± 9.3% versus 50.1 ± 6.3%, p = 0.008, adjusted p = 0.048). The VAD of the deeper macular, papillary, and peripapillary layers showed no differences between the affected and non-affected eyes. The mean deviation and the retinal nerve fibre layer thickness had correlations with the VAD of the macula (r = 0.451, p = 0.001, r = 0.553, p < 0.001), the peripapillary SCV (r = 0.430, p = 0.002, r = 0.723, p < 0.001), and the papillary region (r = 0.512, p < 0.001, r = 0.292, p = 0.039). Patients receiving systemic antiviral therapy (SAT) showed better VAD of the peripapillary choriocapillary layer (p = 0.001, no therapy: 31.4 ± 1.9%, SAT: 35.0 ± 1.6%), and choroidal layer (p = 0.009, no therapy: 34.2 ± 0.3%, SAT: 36.3 ± 1.8%) compared to those with no SAT.

CONCLUSION

A lower peripapillary VAD in the SVC might indicate vascular dysfunction as a sign of glaucomatous damage. SAT might have positive effects on the microcirculation in the deep retinal and choroidal layers.

TRIAL REGISTRATION

TRN: DRKS00028266, https://www.drks.de/drks_web/ .

Retinal Hydration Assessment With Optical Coherence Tomography: Unraveling Its Significance in Retinal Fluid Dynamics, Macular Edema and Cell Viability

PURPOSE

The purpose of this study was to quantify retinal hydration (RH) levels with optical coherence tomography (OCT) and determine the extent of cellular damage resulting from intraretinal fluid alterations.

METHODS

We took 6.0 mm sections of the human sensory retina that were excised from 18 fresh (<24 hours) donor eyes. They were either exposed to various osmotic stresses between 90 and 305 mOsm or dehydrated under a laminar flow hood. Change in tissue weight was used to calculate the retinal water content (RWC). Image analyses were conducted on OCT between 0 and 180 minutes to assess retinal thickness (RT) and "optically empty areas" (OEAs) representing intraretinal fluid. Correlations were sought among RWC, OEA, RWC, and RT. The effect of RH on retinal cell viability (RCV) was assessed with the Live-Dead Assay.

RESULTS

RH demonstrated a stronger correlation with the OEA than plain RT measurements (r = 0.99, P < 0.001). RH-RCV interaction fits well to a bell-shaped curve. A significant proportion of retinal cells (>80%) remained viable despite the change in RH ranging between 0.87 and 1.42 times. This "safe zone" was found to be associated with a 22% increase in OEA (r = 0.99, P < 0.01).

CONCLUSIONS

OCT has been demonstrated as a valuable tool for assessing RH and can be used for intraretinal fluid content analysis. RH is a better indicator of RCV compared with RT. Computing RH may improve the determination of functional outcome of intravitreal pharmacotherapeutics used for diabetic macular edema and exudative age-related macular degeneration.

TRANSLATIONAL RELEVANCE

We link basic research and clinical care by assessing retinal hydration's impact on retinal fluid dynamics, macular edema, and cell viability.

Quantitative Parameters Relevant for Diabetic Macular Edema Evaluation by Optical Coherence Tomography Angiography

Diabetic macular edema (DME) is one of the main ocular complications of diabetes mellitus (DM) that can lead to important vision loss in diabetic patients. In clinical practice, there are cases of DME with unsatisfying treatment responses, despite adequate therapeutic management. Diabetic macular ischemia (DMI) is one of the causes suggested to be associated with the persistence of fluid accumulation. Optical coherence tomography angiography (OCTA) is a non-invasive imaging modality, able to give in-depth information about retinal vascularization in a 3-dimensional manner. The OCTA devices currently available can provide various OCTA metrics that quantitatively assess the retinal microvasculature. In this paper, we reviewed the results of multiple studies that investigated the changes in OCTA metrics in the setting of DME and their possible contribution to the diagnosis, therapeutic management, follow-up and prognosis of patients with DME. We analyzed and compared relevant studies that investigated OCTA parameters related to changes in macular perfusion in the setting of DME and we evaluated the correlations between DME and several quantitative parameters, such as vessel density (VD), perfusion density (PD), foveal avascular zone (FAZ)-related parameters, as well as complexity indices of retinal vasculature. The results of our research showed that OCTA metrics, evaluated especially at the level of the deep vascular plexus (DVP), are useful instruments that can contribute to the assessment of patients with DME.

Associations between macular retinal vasculature and severity of idiopathic epiretinal membrane

BACKGROUND

To demonstrate the associations between the morphology of macular retinal vasculature and disease severity of idiopathic epiretinal membrane (ERM).

METHODS

Macular structures were assessed using optical coherence tomography (OCT), and were classified as "with pseudohole" or "without pseudohole". The 3 × 3 mm macular OCT angiography images were analyzed using the Fiji software to obtain the vessel density, skeleton density, average vessel diameter, vessel tortuosity, fractal dimension, and foveal avascular zone (FAZ)-related parameters. The correlations between these parameters and ERM grading as well as visual acuity were analyzed.

RESULTS

For ERM with or without a pseudohole, increased average vessel diameter, decreased skeleton density, and decreased vessel tortuosity were all associated with inner retinal folding and thickened inner nuclear layer, indicating more severe ERM. In 191 eyes without a pseudohole, the average vessel diameter increased, fractal dimension decreased and vessel tortuosity decreased with increasing ERM severity. The FAZ was not associated with ERM severity. Decreased skeleton density (r = -0.37), vessel tortuosity (r = -0.35), and increased average vessel diameter (r = 0.42) were correlated with worse visual acuity (All P < 0.001). In 58 eyes with pseudoholes, a larger FAZ was associated with a smaller average vessel diameter (r = -0.43, P = 0.015), higher skeleton density (r = 0.49, P < 0.001), and vessel tortuosity (r = 0.32, P = 0.015). However, none of the retinal vasculature parameters correlated with visual acuity and central foveal thickness.

CONCLUSION

Increased average vessel diameter, decreased skeleton density, decreased fractal dimension and decreased vessel tortuosity were good indicators of ERM severity and associated visual impairment.