TOMOGRAPHIC RELATIONSHIPS BETWEEN RETINAL NEOVASCULARIZATION AND THE POSTERIOR VITREOUS IN PROLIFERATIVE DIABETIC RETINOPATHY

Optical coherence tomography angiography in the diagnosis of ocular disease

Clinical imaging provided by optical coherence tomography (OCT) and its variant, OCT-angiography (OCT-A), has revolutionised eyecare practice. The imaging techniques allow for the identification and quantification of ocular structures, supporting the diagnosis and prognosis of eye disease. In this review, an overview of the usefulness of OCT-A imaging in the diagnosis and management of a range of ocular conditions is provided when used in isolation or in combination with other imaging modalities and measures of visual function (visual field results). OCT-A imaging has the capacity to identify and quantify ocular vasculature non-invasively, thereby assisting the clinician in the diagnosis or to determine the efficacy of intervention in ocular conditions impacting retinal vasculature. Thus, additional clinically useful information can be obtained in eye diseases involving conditions such as those impacting retinal vessel occlusion, in diabetic retinopathy, inherited retinal dystrophy, age-related macular degeneration, choroidal neovascularisation and optic nerve disorders. Through a clinical case series, various ocular conditions are reviewed, and the impact of OCT-A imaging is discussed. Although OCT-A imaging has great promise and is already used in clinical management, there is a lack of set standards to characterise altered vascular features in disease and consequently for prognostication, primarily due to a lack of large-scale clinical trials and variability in OCT-A algorithms when generating quantitative parameters.

Investigating the Utility of Near-Infrared Reflectance Imaging for Diabetic Retinopathy Screening

BACKGROUND AND OBJECTIVE

We investigated the reliability of near-infrared reflectance (NIR) imaging as a method of assessing severity of diabetic retinopathy (DR).

PATIENTS AND METHODS

One hundred ninety-five NIR images were reviewed by two graders for the number of hyporeflective foci, presence or absence of vascular abnormalities, and presumptive DR stage; these were correlated to fundus photography-defined DR stage. Interrater reliability was confirmed via one-way random effects model of intraclass correlation coefficients. Analysis of variance was used in subgroup analysis, receiver operating characteristic (ROC) curves were created to validate reliability of the model, and logistic regression was used to model foci and vascular abnormalities as predictors for moderate or worse disease.

RESULTS

A statistically significant difference in mean number of hyporeflective foci was found between no DR and moderate non-proliferative DR (NPDR; P < 0.0001), no DR and severe NPDR (P < 0.001), no DR and proliferative DR (PDR; P < 0.0001), mild and moderate NPDR (P = 0.008), mild and severe NPDR (P < 0.001), and mild NPDR and PDR (P < 0.001). The area under the ROC curve was 0.849 (CI: 0.792 to 0.905). The threshold for detection of moderate NPDR or worse was 4.75 foci, with a sensitivity of 79.0% and a false positive rate of 20.0%. Multivariate logistic regression model incorporating hyporeflective foci with vascular abnormalities (odds ratio [OR] = 1.592, 95% CI: 1.381 to 1.835; P < 0.001) was able to accurately predict moderate disease or worse, just moderate disease (OR = 1.045, 95% CI: 1.003 to 1.089; P = 0.035), severe disease (OR = 1.050, 95% CI: 1.006 to 1.096; P = 0.027), and proliferative disease (OR = 1.050, 95% CI: 1.008 to 1.095; P = 0.018).

CONCLUSIONS

NIR imaging may be an adjunct tool in screening for DR. [Ophthalmic Surg Lasers Imaging Retina 2024;55:318-325.].

Practical Utility of Widefield OCT Angiography to Detect Retinal Neovascularization in Eyes with Proliferative Diabetic Retinopathy

PURPOSE

To assess the real clinical utility of widefield OCT angiography (WF-OCTA) for detecting retinal neovascularization (RNV) in eyes with proliferative diabetic retinopathy (PDR).

DESIGN

A retrospective cross sectional study.

PARTICIPANTS

Consecutive eyes clinically suspected of PDR by physicians at a tertiary eye center between March 2021 and November 2022.

METHODS

All eyes underwent ultrawidefield fluorescein angiography (UWF-FA) (California, Optos) and WF-OCTA (S1, Canon) with a 23 × 20 mm scan area. Two independent graders detected individual RNV lesions using UWF-FA and used them as the ground truth. Widefield OCT angiography images were first evaluated to determine whether the images successfully illustrated retinal vasculature, regardless of the image quality index or the presence of vitreous hemorrhage. The graders then identified the RNV lesions with WF-OCTA. We detected RNV by utilizing both the entire retinal slab, including flow signals in the retina, and the custom vitreoretinal interface slab, defined as flow signals from 20 μm below the internal limiting membrane (ILM) to 2000 μm above the ILM. We evaluated the applicability to real clinical practice by not correcting segmentation errors.

MAIN OUTCOME MEASURES

The success rate of imaging and the detection rate of RNV using WF-OCTA.

RESULTS

Initially, 69 consecutive patients who underwent UWF-FA were identified. Of these, 114 eyes from 57 (83%) patients underwent both UWF-FA and WF-OCTA. Of the 114 eyes, 108 (95%) produced gradable WF-OCTA images. Using UWF-FA, the graders identified 175 RNV lesions in 40 eyes. Widefield OCT angiography achieved a sensitivity of 95% and specificity of 88% for detecting eyes with RNV. At the level of individual RNV lesions, graders detected 156 RNV lesions with WF-OCTA, with 118 of these confirmed by UWF-FA (true positive). Among the 57 false-negative lesions, the primary causes were being out of the scan range (26 lesions) and segmentation errors (21 lesions).

CONCLUSIONS

Widefield OCT angiography imaging had a high success rate, achieving a sensitivity of 95% and a specificity of 88% for detecting eyes with RNV in a real clinical setting. Despite a 67% detection rate for individual RNV lesions, WF-OCTA may serve as a valuable noninvasive method for RNV detection in eyes with diabetic retinopathy.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Widefield swept-source optical coherence tomography angiography metrics associated with neovascular glaucoma in patients with proliferative diabetic retinopathy

PURPOSE

To explore the association between widefield swept-source optical coherence tomography angiography (WF SS-OCTA) metrics, including nonperfusion area (NPA) and neovascularization (NV), and presence of neovascular glaucoma (NVG) in patients with proliferative diabetic retinopathy (PDR).

METHODS

A prospective, cross-sectional study was conducted from November 2018 to February 2020. A total of 85 eyes of 60 PDR patients without NVG and 9 eyes of 8 PDR patients with NVG were included. Retinal ischemic parameters (NPA; ischemia index [NPA/total retinal area]) and NV features (NV number; NV area; NV vessel density) were evaluated. Foveal avascular zone (FAZ), macular thickness/volume, and choroidal thickness/volume were obtained using the Zeiss ARI Network. WF SS-OCTA retinal and choroidal metrics, systemic, and ocular parameters were screened using Least Absolute Shrinkage and Selection Operator (LASSO) logistic regression for variable selection. Firth's bias-reduced logistic regression (outcome: presence of NVG) was subsequently used to identify parameters associated with NVG.

RESULTS

After LASSO variable selection, 8 variables were significantly associated with the presence of NVG: DM duration (years), insulin (yes/no), best-corrected visual acuity (BCVA) (logMAR), IOP, ischemia index, skeletonized vessel density, macular thickness (inner inferior, outer temporal regions). Firth's bias-reduced logistic regression showed ischemia index (odds ratio [OR]=13.2, 95% confidence interval [CI]:5.3-30.7, P<0.001) and BCVA (OR=5.8, 95%CI:1.2-28.8, P<0.05) were associated with the presence of NVG. NV metrics, FAZ, and choroidal parameters were not related to NVG.

CONCLUSIONS

Retinal ischemia but not NV was associated with the presence of NVG in patients with PDR using WF SS-OCTA. Larger, longitudinal studies are needed to validate imaging biomarkers associated with diabetic NVG.

Vitreous hemorrhage in retinal vein occlusion without visible traction from the posterior vitreous membrane: An optical coherence tomography angiography case report study

Background

We report an unusual case of retinal vein occlusion (RVO) associated with vitreous hemorrhage (VH) without visible traction from the posterior vitreous membrane (PVM) at the bleeding point, challenging our current understanding of VH pathophysiology.

Case presentation

A 52-year-old man presented with VH in the right eye. A detailed examination using optical coherence tomography angiography (OCTA) and ultra-widefield fluorescein angiography revealed branch RVO with non-perfused areas (NPAs) extending peripherally and neovascularization elsewhere (NVE). OCTA showed NVE infiltrating the vitreous cavity, leading to substantial bleeding without visible PVM traction at the bleeding point. The NVE was successfully removed following vitrectomy, and visual acuity improved from 20/20 to 20/13 preoperatively, along with a postoperative improvement in floaters.

Conclusions

This unique case of RVO suggests the possibility of VH occurring independent of PVM contractions at the bleeding point, challenging the traditional understanding of VH. This finding underscores the potential role of OCTA in diagnosing and managing retinal vascular diseases, underscoring the need for further investigations into the underlying mechanisms, with potential implications for personalized therapeutic strategies.

A Pixel-Based Machine-Learning Model For Three-Dimensional Reconstruction of Vitreous Anatomy

Purpose

To develop a machine-learning image processing model for three-dimensional (3D) reconstruction of vitreous anatomy visualized with swept-source optical coherence tomography (SS-OCT).

Methods

Healthy subjects were imaged with SS-OCT. Scans of sufficient quality were transferred into the Fiji is just ImageJ image processing toolkit, and proportions of the resulting stacks were adjusted to form cubic voxels. Image-averaging and Trainable Weka Segmentation using Sobel and variance edge detection and directional membrane projections filters were used to enhance and interpret the signals from vitreous gel, liquid spaces within the vitreous, and interfaces between the former. Two classes were defined: "Septa" and "Other." Pixels were selected and added to each class to train the classifier. Results were generated as a probability map. Thresholding was performed to remove pixels that were classified with low confidence. Volume rendering was performed with TomViz.

Results

Forty-seven eyes of 34 healthy subjects were imaged with SS-OCT. Thirty-four cube scans from 25 subjects were of sufficient quality for volume rendering. Clinically relevant vitreous features including the premacular bursa, area of Martegiani, and prevascular vitreous fissures and cisterns, as well as varying degrees of vitreous degeneration were visualized in 3D.

Conclusions

A machine-learning model for 3D vitreous reconstruction of SS-OCT cube scans was developed. The resultant high-resolution 3D movies illustrated vitreous anatomy in a manner like triamcinolone-assisted vitrectomy or postmortem dye injection.

Translational Relevance

This machine learning model now allows for comprehensive examination of the vitreous structure beyond the vitreoretinal interface in 3D with potential applications for common disease states such as the vitreomacular traction and Macular Hole spectrum of diseases or proliferative diabetic retinopathy.

Detection of neovascularisation in the vitreoretinal interface slab using widefield swept-source optical coherence tomography angiography in diabetic retinopathy

AIMS

To compare the efficacy of diabetic retinal neovascularisation (NV) detection using the widefield swept-source optical coherence tomography angiography (WF SS-OCTA) vitreoretinal interface (VRI) Angio slab and SS-OCT VRI Structure slab.

METHODS

A prospective, observational study was performed at Massachusetts Eye and Ear from January 2019 to June 2020. Patients with proliferative diabetic retinopathy (PDR), patients with non-proliferative diabetic retinopathy and patients with diabetes but without diabetic retinopathy were included. All patients were imaged with WF SS-OCTA using the 12×12 mm Angio scan protocol centred on the fovea and optic disc. The en-face SS-OCTA VRI Angio slab and SS-OCT VRI Structure slab were evaluated for the presence or absence of NV. SS-OCTA B-scan was used to classify NV according to cross-sectional morphology (forward, tabletop or flat). All statistical analyses were performed using SPSS V.26.0.

RESULTS

One hundred and forty-two eyes of 89 participants were included in the study. VRI Angio detected NV at higher rates compared with VRI Structure (p<0.05). Combining VRI Angio and Structure improved detection rates compared with VRI Angio alone (p<0.05). Due to segmentation errors of the internal limiting membrane, NV with flat morphological classification had lower rates of detection on VRI Angio compared with NV with forward and tabletop morphology (p<0.05).

CONCLUSIONS

WF SS-OCTA 12×12 mm VRI Angio and SS-OCT VRI Structure imaging centred on the fovea and optic disc detected NV with high sensitivity and low false positives. The VRI slab may be useful to diagnose and monitor PDR in clinical practice.

Update on Optical Coherence Tomography and Optical Coherence Tomography Angiography Imaging in Proliferative Diabetic Retinopathy

Proliferative diabetic retinopathy (PDR) is a major cause of blindness in diabetic individuals. Optical coherence tomography (OCT) and OCT-angiography (OCTA) are noninvasive imaging techniques useful for the diagnosis and assessment of PDR. We aim to review several recent developments using OCT and discuss their present and potential future applications in the clinical setting. An electronic database search was performed so as to include all studies assessing OCT and/or OCTA findings in PDR patients published from 1 January 2020 to 31 May 2021. Thirty studies were included, and the most recently published data essentially focused on the higher detection rate of neovascularization obtained with widefield-OCT and/or OCTA (WF-OCT/OCTA) and on the increasing quality of retinal imaging with quality levels non-inferior to widefield-fluorescein angiography (WF-FA). There were also significant developments in the study of retinal nonperfusion areas (NPAs) using these techniques and research on the impact of PDR treatment on NPAs and on vascular density. It is becoming increasingly clear that it is critical to use adequate imaging protocols focused on optimized segmentation and maximized imaged retinal area, with ongoing technological development through artificial intelligence and deep learning. These latest findings emphasize the growing applicability and role of noninvasive imaging in managing PDR with the added benefit of avoiding the repetition of invasive conventional FA.

Comparison of Posterior Hyaloid Assessment Using Preoperative Optical Coherence Tomography and Intraoperative Triamcinolone Acetonide Staining During Vitrectomy

Purpose

To compare the specificity of diagnosing posterior vitreous detachment (PVD) using preoperative optical coherence tomography (OCT) versus intraoperative triamcinolone acetonide (TA) staining in patients undergoing vitrectomy.

Patients and Methods

This retrospective cohort study included patients undergoing pars plana vitrectomy for diverse retinal pathologies. Intraoperatively, surgeons evaluated the posterior hyaloid status with TA staining and compared it with preoperative OCT findings.

Results

One hundred six patients underwent intraoperative assessments of posterior hyaloid status, with 72% (76/106) of the eyes showing positive staining. Sixty-two patients had also undergone preoperative OCT. Of the patients diagnosed with PVD on preoperative OCT, 50% (15/30) showed positive TA staining intraoperatively. The sensitivity of preoperative OCT assessment was 83.3%, and its specificity was 65.9%.

Conclusion

Preoperative OCT imaging is associated with lower sensitivity and specificity for diagnosing PVD when compared to intraoperative TA staining.

Management of Complications and Vision Loss from Proliferative Diabetic Retinopathy

PURPOSE OF REVIEW

Diabetes can be associated with profound visual loss due to several mechanisms. As the duration of diabetes and blood glucose levels increase, these changes become more severe. The proliferation of new blood vessels, vitreous hemorrhage, and tractional retinal detachments may ultimately result and can be devastating to visual function. New advances, including anti-vascular endothelial growth factor (VEGF) medications and innovative microsurgical instruments, have provided additional methods for the management of diabetic retinopathy in the clinic and in the operating room, leading to improved outcomes.

RECENT FINDINGS

Advances in earlier treatment of proliferative diabetic retinopathy, especially with anti-VEGF injections, allow for a reduction in severity, improved vision, and more controlled and successful surgery. Modern surgical techniques and instrumentation have also allowed for improved patient outcomes. Future research into sustained delivery and release of anti-VEGF, reducing the need for frequent in-office injections, may prove to be additionally beneficial. Over the last decade, anti-VEGF has become an increasingly common treatment modality for the management of proliferative diabetic retinopathy, vitreous hemorrhages, and tractional retinal detachments. Further research is needed to determine the ideal method of delivery and timing of the treatment.

NOVEL THREE TYPES OF NEOVASCULARIZATION ELSEWHERE DETERMINE THE DIFFERENTIAL CLINICAL FEATURES OF PROLIFERATIVE DIABETIC RETINOPATHY

PURPOSE

To explore the pathological features and clinical significance of three types of neovascularization elsewhere (NVE) in proliferative diabetic retinopathy.

METHODS

Neovascularization elsewhere was classified based on the origins and morphologic features using fluorescein angiography and angiographic and structural optical coherence tomography. The topographical distribution, vitreoretinal interface, and responsiveness to panretinal photocoagulation were compared among three types of NVE.

RESULTS

One hundred and twenty-seven NVEs were classified into three types. Type 1 NVE was concentrated along or adjacent to vascular arcades; Type 2 was distributed more peripherally than were Types 1 and 3 NVE. The arch bridge-like vitreoretinal interface accounted for 79% of Type 1 NVE. The flat and flat-forward vitreoretinal interface accounted for 95% and 100% in Type 2 and Type 3 NVE, respectively. At 3 months after panretinal photocoagulation, the regression rates for Types 1, 2, and 3 NVE were 82%, 100%, and 80%, respectively. Type 2 NVE showed best regression rate after panretinal photocoagulation (both P < 0.01).

CONCLUSION

Three types of NVE determine the distinctly topographical distributions, vitreoretinal interface features, and differential responsiveness to panretinal photocoagulation treatment. This new concept may have important clinical implications in assessing the treatment and prognosis of proliferative diabetic retinopathy.

Widefield Swept-Source OCT Angiography Metrics Associated with the Development of Diabetic Vitreous Hemorrhage: A Prospective Study

PURPOSE

To investigate the association among widefield swept-source (SS) OCT angiography (OCTA) metrics and systemic parameters and vitreous hemorrhage (VH) occurrence in eyes with proliferative diabetic retinopathy (PDR).

DESIGN

Prospective, observational study.

PARTICIPANTS

Fifty-five eyes from 45 adults with PDR, with no history of VH, followed up for at least 3 months.

METHODS

All patients underwent widefield SS OCTA (Montage 15 × 15 mm and high-definition (HD)-51 line scan) imaging. Images were evaluated independently by 2 graders for quantitative and qualitative widefield SS OCTA metrics defined a priori. Systemic and ocular parameters and widefield SS OCTA metrics were screened using least absolute shrinkage and selection operator and logistic or Cox regression for variable selection. Firth's bias-reduced logistic regression models (outcome, occurrence of VH) and Cox regression models (outcome, time to occurrence of VH) were used to identify parameters associated with VH occurrence.

MAIN OUTCOME MEASURES

Occurrence of VH.

RESULTS

Over a median follow-up of 363 days (range, 28-710 days), 13 of 55 PDR eyes (24%) demonstrated VH during the follow-up period. Presence of extensive neovascularizations (odds ratio, 8.05; 95% confidence interval [CI], 1.43-58.56; P = 0.02), defined as neovascularizations with total area of more than 4 disc diameters, and forward neovascularizations (odds ratio, 5.42; 95% CI, 1.26-35.16; P = 0.02) that traversed the posterior hyaloid face into the vitreous were associated with the occurrence of VH. The presence of flat neovascularizations (odds ratio, 0.25; 95% CI, 0.04-1.01; P = 0.05) confined to the posterior hyaloid face was associated with a lower risk of VH with borderline significance. Similarly, presence of extensive neovascularizations (hazard ratio, 18.24; 95% CI, 3.51-119.47; P < 0.001) and forward neovascularizations (hazard ratio, 9.60; 95% CI, 2.07-68.08; P = 0.002) was associated significantly with time to development of VH.

CONCLUSIONS

Widefield SS OCTA is useful for evaluating neovascularizations and their relationship with the vitreous. The presence of forward and extensive neovascularizations was associated with the occurrence of VH in patients with PDR. Larger samples and longer follow-up are needed to verify the risk factors and imaging biomarkers for diabetic VH.

Retinal applications of swept source optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA)

The advent of optical coherence tomography (OCT) revolutionized both clinical assessment and research of vitreoretinal conditions. Since then, extraordinary advances have been made in this imaging technology, including the relatively recent development of swept-source OCT (SS-OCT). SS-OCT enables a fast scan rate and utilizes a tunable swept laser, thus enabling the incorporation of longer wavelengths than conventional spectral-domain devices. These features enable imaging of larger areas with reduced motion artifact, and a better visualization of the choroidal vasculature, respectively. Building on the principles of OCT, swept-source OCT has also been applied to OCT angiography (SS-OCTA), thus enabling a non-invasive in depth-resolved imaging of the retinal and choroidal microvasculature. Despite their advantages, the widespread use of SS-OCT and SS-OCTA remains relatively limited. In this review, we summarize the technical details, advantages and limitations of SS-OCT and SS-OCTA, with a particular emphasis on their relevance for the study of retinal conditions. Additionally, we comprehensively review relevant studies performed to date to the study of retinal health and disease, and highlight current gaps in knowledge and opportunities to take advantage of swept source technology to improve our current understanding of many medical and surgical chorioretinal conditions. We anticipate that SS-OCT and SS-OCTA will continue to evolve rapidly, contributing to a paradigm shift to more widespread adoption of new imaging technology to clinical practice.

Near-infrared reflectance imaging of neovascularization in proliferative diabetic retinopathy

Background

Blood is one of the main absorbers in the near-infrared spectrum and thus retinal vessels appear dark in near-infrared reflectance (NIR) images. Proliferative diabetic retinopathy (PDR) is characterized by abnormal neovascularization which also absorbs light and appears dark against a lighter fundus background. We analyzed neovascularization in PDR using NIR imaging, by observing changes in the neovascular complexes (NVCs) contrast and reflectivity over time.

Methods

Retrospective case series of 20 eyes of 17 patients with PDR who underwent NIR imaging with optical coherence tomography (OCT) using the Spectralis System. NVCs presence and activity was determined using clinical, tomographic and angiographic criteria. At baseline, all NVCs were qualitatively graded in the NIR image into 3 groups (absent, present and inactive and present and active) and their evolution over time was registered as progression, regression or same status.

Results

Twenty-seven NVCs were imaged, of which, 52% were neovascularization of the disc (NVD) and 48% were elsewhere (NVE). Consecutive NIR images were obtained from baseline to up to 5 time-points with a mean follow-up of 3.2 ± 1.7 years. All eyes underwent laser treatment and 30% had additional intravitreal therapy. Using NIR imaging, NVCs were classified at baseline as absent, present and inactive and present and active, respectively in 11, 4 and 85% of cases. NIR identified active neovascularization as hyporeflective irregular dark vessels originating from the retinal venules in NVE or from the disc in NVD. In all groups during follow-up, progression was identified as the development of new vascular hyporeflective dark fronds while regression was shown by reduced dark perfusion. Five eyes developed a wolf’s jaw configuration with vascular hyporeflective new vessels and hyperreflective tissue from extensive fibrosis. Fibrosis was more apparent in later images, reaching 86%. In 3 cases (11%), the NVC was no longer seen in NIR, although was still identifiable on OCT over the NVC area.

Conclusions

NIR is a non-invasive imaging modality commonly performed alongside OCT and frequently overlooked which can be useful to evaluate NVCs in PDR. Changes in NVC contrast and reflectivity due to blood perfusion can help in the detection and monitoring of diabetic proliferative disease and aid clinicians in daily practice.

Optical Coherence Tomography Angiography Features of Neovascularization in Proliferative Diabetic Retinopathy

Purpose

To describe features of neovascularization in proliferative diabetic retinopathy (PDR) using optical coherence tomography angiography (OCTA).

Methods

A retrospective case series was performed in 23 eyes from 21 patients who underwent OCTA of neovascular complexes (NVCs) due to PDR. Eyes were imaged with the DRI Triton swept-source OCTA, Avanti RTVue XR or Cirrus HD-OCT 5000 as part of routine clinical examination. Segmentation was adjusted to include vasculature between the vitreous cavity and the internal limiting membrane (ILM). The presence of NVCs was confirmed by clinical examination and multimodal imaging such as color or red-free fundus photography, fluorescein angiography, multicolor imaging or near-infrared reflectance.

Results

Thirty-five NVCs were imaged, of which, 34% were neovascularization of the disc (NVD) and 66% were neovascularization elsewhere (NVE). On structural OCT B-scans, NVE appeared as medium to highly reflective tissue that breached the ILM, while NVD showed highly reflective tissue protruding from the disc in a sea fan configuration. Flow signal was seen on OCTA in all cases of NVE and in 67% of NVD lesions. Areas with minimal or absent retinal flow signal identified retinal nonperfusion areas and were found adjacent to 87% of NVE. Intraretinal microvascular abnormalities (IRMAs) were noted next to 70% of NVE. Absent flow signal was seen in 4 NVD cases showing posterior shadowing and were considered inactive.

Conclusion

OCTA appears useful for imaging NVCs, IRMAs, and retinal nonperfusion areas in eyes with diabetic retinopathy. This imaging modality enables noninvasive screening and monitoring of PDR and can obviate the need for additional testing in certain clinical settings.

Optical coherence tomography features of neovascularization in proliferative diabetic retinopathy: a systematic review

Background

Diabetic retinopathy (DR) is a leading cause of blindness due to diabetic macular edema (DME) or complications of proliferative diabetic retinopathy (PDR). Optical coherence tomography (OCT) is a noninvasive imaging technique well established for DME but less used to assess neovascularization in PDR. Developments in OCT imaging and the introduction of OCT angiography (OCTA) have shown significant potential in PDR.

Objectives

To describe the tomographic features of PDR, namely of neovascularization, both of the optic disc (NVD) and elsewhere (NVE), intraretinal microvascular abnormalities (IRMA), retinal nonperfusion areas (NPA), status of the posterior vitreous, vitreoschisis and vitreous and subhyaloid/sub-ILM hemorrhages.

Data sources

Electronic database search on PubMed and EMBASE, last run on December 19th 2019.

Study eligibility criteria, participants and interventions

Publications assessing OCT and/or OCTA findings in PDR patients. All study designs were allowed except for case-reports, conference proceedings and letters.

Study appraisal

Newcastle–Ottawa Scale for observational studies was used for purposes of risk of bias assessment.

Results

From the 1300 studies identified, 283 proceeded to full-text assessment and 60 were included in this comprehensive review. OCT was useful in detecting NVD and NVE, such as in characterizing disease activity and response to laser and/or anti-VEGF therapies. The absence of posterior vitreous detachment seemed determinant for neovascular growth, with the posterior hyaloid acting as a scaffold. OCTA allowed a more detailed characterization of the neovascular complexes, associated NPA and disease activity, allowing the quantification of neovessel area and flow index. However, changes in OCTA blood flow signal following local therapies did not necessarily correlate with structural regression. Widefield and ultra-widefield OCTA were highly sensitive in the detection of PDR, adding value to disease staging and monitoring. Compared to fluorescein angiography, OCTA was more sensitive in detecting microvascular changes indicating disease progression.

Limitations

Publication languages were restricted. Most included studies were observational and non-comparative. Risk of bias regarding case representativeness.

Conclusions

OCT-based retinal imaging technologies are advancing rapidly and the trend is to be noninvasive and wide-field. OCT has proven invaluable in diagnosing, staging and management of proliferative diabetic disease with daily application in clinical and surgical practices.

Vitreous and Vision Degrading Myodesopsia

Macromolecules comprise only 2% of vitreous, yet are responsible for its gel state, transparency, and physiologic function(s) within the eye. Myopia and aging alter collagen and hyaluronan association causing concurrent gel liquefaction and fibrous degeneration. The resulting vitreous opacities and collapse of the vitreous body during posterior vitreous detachment are the most common causes for the visual phenomenon of vitreous floaters. Previously considered innocuous, the vitreous opacities that cause floaters sometimes impact vision by profoundly degrading contrast sensitivity function and impairing quality-of-life. While many people adapt to vitreous floaters, clinically significant cases can be diagnosed with Vision Degrading Myodesopsia based upon echographic assessment of vitreous structure and by measuring contrast sensitivity function. Perhaps due to the ubiquity of floaters, the medical profession has to date largely ignored the plight of those with Vision Degrading Myodesopsia. Improved diagnostics will enable better disease staging and more accurate identification of severe cases that merit therapy. YAG laser treatments may occasionally be slightly effective, but vitrectomy is currently the definitive cure. Future developments will usher in more informative diagnostic approaches as well as safer and more effective therapeutic strategies. Improved laser treatments, new pharmacotherapies, and possibly non-invasive optical corrections are exciting new approaches to pursue. Ultimately, enhanced understanding of the underlying pathogenesis of Vision Degrading Myodesopsia should result in prevention, the ultimate goal of modern Medicine.

Objective Evaluation of Proliferative Diabetic Retinopathy Using OCT

PURPOSE

To present the routine use of OCT and OCT angiography (OCTA) for the objective diagnosis and monitoring of proliferative diabetic retinopathy (PDR).

DESIGN

Retrospective, observational case series.

PARTICIPANTS

Patients with diabetic retinopathy imaged using a standardized PDR protocol.

METHODS

Patients routinely imaged with a standardized PDR protocol between March 2017 and January 2019 were included. This included a 12×9-mm structural OCT volume centered on the macula and a 6×6-mm OCTA scan centered on the optic nerve head obtained using a Topcon swept-source system (DRI OCT-1 Triton, Topcon, Tokyo, Japan). Ultra-widefield fluorescein angiography (FA) was also performed when clinically indicated. The ground truth for each case was determined by merging the findings from biomicroscopy and imaging modalities to generate the maximum level of detection for each finding.

MAIN OUTCOME MEASURES

Detection rates of new-onset, regression, and reactivation of neovascularization of the disc (NVD) and neovascularization elsewhere (NVE) using different modalities (biomicroscopy/color photography, structural OCT, B-scan OCTA, en face OCTA). Detection of progression of tractional retinal detachment (TRD).

RESULTS

A total of 383 eyes of 204 patients were evaluated. After excluding patients without PDR or with insufficient image quality, 47 eyes of 35 patients were included. For the detection of new-onset NVD and NVE, structural OCT had the highest detection rate (100%) of all modalities. However, for the detection of regression or reactivation of neovascularization (NV), B-scan OCTA had the highest detection rate (100%). Structural OCT detected regression only in 45.5% of cases, resulting in a low detection rate of reactivation (12.5%). Among 10 eyes with TRD, OCT detected fovea-threatening TRD during follow-up in 7 eyes, resulting in vitrectomy.

CONCLUSIONS

This study demonstrates the utility of novel multimodal imaging in the daily management of patients with PDR. Posterior pole structural OCT had the best detection rate for NV, and B-scan OCTA showed the most potential for objective monitoring of disease after treatment.

Müller cells in pathological retinal angiogenesis

Müller cells are the major glial cells spanning the entire layer of the retina and maintaining retinal structure. Under pathological conditions, Müller cells are involved in retinal angiogenesis, a process of growing new blood vessels from pre-existing capillaries. In response to hypoxia, high glucose, and inflammation conditions, multiple signaling pathways are activated in Müller cells, followed by the increased production of proangiogenic factors including vascular endothelial growth factor, basic fibroblast growth factor, matrix metalloproteinases, Netrin-4, and angiopoietin-like 4. Expression of antiangiogenic factors is also downregulated in Müller cells. Besides, proliferation and dedifferentiation of Müller cells facilitates retinal angiogenesis. In this review, we summarized molecular mechanisms of Müller cells-related retinal angiogenesis. The potential of Müller cells as a therapeutic target for retinal angiogenesis was also discussed.

An evidence-based approach to the routine use of optical coherence tomography

Optical coherence tomography is an imaging technology that has revolutionised the detection, assessment and management of ocular disease. It is now a mainstream technology in clinical practice and is performed by non-specialised personnel in some settings. This article provides a clinical perspective on the implications of that movement and describes best practice using multimodal imaging and an evidence-based approach. Practical, illustrative guides on the interpretation of optical coherence tomography are provided for three major diseases of the ocular fundus, in which optical coherence tomography is often crucial to management: age-related macular degeneration, diabetic retinopathy and glaucoma. Topics discussed include: cross-sectional and longitudinal signs in ocular disease, so-called 'red-green' disease whereby clinicians rely on machine/statistical comparisons for diagnosis in managing treatment-naïve patients, and the utility of optical coherence tomography angiography and machine learning.

Characteristics of Neovascularization in Early Stages of Proliferative Diabetic Retinopathy by Optical Coherence Tomography Angiography

PURPOSE

To classify retinal neovascularization in untreated early stages of proliferative diabetic retinopathy (PDR) based on optical coherence tomography angiography (OCTA).

DESIGN

A cross-sectional study.

METHODS

Thirty-five eyes were included. They underwent color fundus photography, fluorescein angiography (FA), and OCTA examinations. Neovascularizations elsewhere (NVEs), neovascularizations at the disc (NVDs), and intraretinal microvascular abnormalities (IRMAs) were scanned by OCTA. The origin and morphology of NVE/NVD/IRMA on OCTA were evaluated. Retinal nonperfusion areas (NPAs) were measured using ImageJ software.

RESULTS

In 35 eyes successfully imaged, 75 NVEs, 35 NVDs, and 12 IRMAs were captured. Three proposed subtypes of NVE were identified based on the origins and morphologic features. Type 1 (32 of 75, 42.67%) originated from the venous side, in a tree-like shape. Type 2 (30 of 75, 40.00%) originated from capillary networks, with an octopus-like appearance. Type 3 (13 of 75, 17.33%) originated from the IRMAs, having a sea fan shape. NVD originated from the retinal artery, from the retinal vein, or from the choroid, and arose from the bending vessels near the rim of the optic disc. IRMA originated from and drained into retinal venules, extending into the retina. The initial layer and affiliated NPA were significantly different in the 3 subtypes of NVEs (all P < .01).

CONCLUSIONS

OCTA allowed identification of the origins and morphologic patterns of neovascularization in PDR. The new classification of retinal neovascularization may be useful to better understand pathophysiological mechanisms and to guide efficient therapeutic strategies.

POSTERIOR PRECORTICAL VITREOUS POCKETS IN HIGH MYOPIA OBSERVED BY ENHANCED VITREOUS IMAGING OF SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY

PURPOSE

To observe the vitreous in highly myopic eyes with posterior precortical vitreous pockets (PPVPs) using enhanced vitreous imaging of spectral domain optical coherence tomography.

METHODS

Fifty-two highly myopic eyes with PPVPs of 36 patients were included in this study. All subjects underwent enhanced vitreous imaging optical coherence tomography. The size of PPVPs was measured, and the frequency of imaging features was recorded.

RESULTS

Nine imaging features of the vitreous in highly myopic eyes with PPVPs were found. The average age of subjects was 38.1 ± 10.8 years. The mean height of PPVPs was 1,177 ± 704 μm, and the mean width was 7,440 ± 755 μm. Hyperreflective line and the interlayer were observed in 30 (57.7%) eyes. Hyperreflective dots were found in 37 (71.2%) eyes. More central vitreous space was more frequently detected in younger patients. Prevascular vitreous fissure was detected in 7 (13.5%) eyes. W-shaped cavity, identified as an empty space with a smooth W-shaped edge, was demonstrated to be the fusion of Cloquet's canal and the extension of PPVPs. Perpendicular hyperreflective parallel strands were detected in 3 (5.8%) eyes. Hyperreflective network was observed in 10 (19.2%) eyes. Hyperreflective parapapillary tubercle was found in 7 (13.5%) eyes.

CONCLUSION

Nine imaging features of the vitreous in highly myopic eyes with PPVPs were visualized by enhanced vitreous imaging optical coherence tomography.