Fluorescein angiography versus optical coherence tomography angiography: FA vs OCTA Italian Study

Optical coherence tomography angiography in diabetic retinopathy: A major review

Diabetic retinopathy (DR) is characterized by retinal vasculopathy and is a leading cause of visual impairment. Optical coherence tomography angiography (OCTA) is an innovative imaging technology that can detect various pathologies and quantifiable changes in retinal microvasculature. We briefly describe its functional principles and advantages over fluorescein angiography and perform a comprehensive review on its clinical applications in the screening or management of people with prediabetes, diabetes without clinical retinopathy (NDR), nonproliferative DR (NPDR), proliferative DR (PDR), and diabetic macular edema (DME). OCTA reveals early microvascular alterations in prediabetic and NDR eyes, which may coexist with sub-clinical neuroretinal dysfunction. Its applications in NPDR include measuring ischemia, detecting retinal neovascularization, and timing of early treatment through predicting the risk of retinopathy worsening or development of DME. In PDR, OCTA helps characterize the flow within neovascular complexes and evaluate their progression or regression in response to treatment. In eyes with DME, OCTA perfusion parameters may be of predictive value regarding the visual and anatomical gains associated with treatment. We further discussed the limitations of OCTA and the benefits of its incorporation into an updated DR severity scale.

Retinal Alterations Predict Early Prodromal Signs of Neurodegenerative Disease

Neurodegenerative diseases are an increasingly common group of diseases that occur late in life with a significant impact on personal, family, and economic life. Among these, Alzheimer's disease (AD) and Parkinson's disease (PD) are the major disorders that lead to mild to severe cognitive and physical impairment and dementia. Interestingly, those diseases may show onset of prodromal symptoms early after middle age. Commonly, the evaluation of these neurodegenerative diseases is based on the detection of biomarkers, where functional and structural magnetic resonance imaging (MRI) have shown a central role in revealing early or prodromal phases, although it can be expensive, time-consuming, and not always available. The aforementioned diseases have a common impact on the visual system due to the pathophysiological mechanisms shared between the eye and the brain. In Parkinson's disease, α-synuclein deposition in the retinal cells, as well as in dopaminergic neurons of the substantia nigra, alters the visual cortex and retinal function, resulting in modifications to the visual field. Similarly, the visual cortex is modified by the neurofibrillary tangles and neuritic amyloid β plaques typically seen in the Alzheimer's disease brain, and this may reflect the accumulation of these biomarkers in the retina during the early stages of the disease, as seen in postmortem retinas of AD patients. In this light, the ophthalmic evaluation of retinal neurodegeneration could become a cost-effective method for the early diagnosis of those diseases, overcoming the limitations of functional and structural imaging of the deep brain. This analysis is commonly used in ophthalmic practice, and interest in it has risen in recent years. This review will discuss the relationship between Alzheimer's disease and Parkinson's disease with retinal degeneration, highlighting how retinal analysis may represent a noninvasive and straightforward method for the early diagnosis of these neurodegenerative diseases.

Feasibility and Clinical Utility of Wide-Field Optical Coherence Tomography Angiography Compared to Ultrawide-Field Fluorescein Angiography in Patients with Diabetic Retinopathy

PURPOSE

To test the diagnostic performance of a novel wide-field swept-source optical coherence tomography angiography (WF-OCTA) device in detecting retinal non-perfusion (NP) and neovascularization (NV) in eyes with diabetic retinopathy (DR) and to compare this with the standard-of-care imaging method, ultrawide-field fluorescein angiography (UWFFA).

METHODS

Prospective, observational, cross-sectional single-center study evaluating patients with DR imaged with WF-OCTA (Xephilio OCT-S1; Canon Inc., Tokyo, Japan) and UWFFA (Optos California; Optos plc, Dunfermline, United Kingdom). WF-OCTA images of the superficial capillary plexus (SCP) consisted of single capture 23 × 20 mm scans centered on the fovea. In UWFFA and WF-OCTA, qualitative and quantitative measurements were assessed to analyze retinal NP and NV. Vessel density (VD) in WF-OCTA and ischemic index (ISI) in UWFFA were calculated. Qualitatively, the presence of NV and NP was assessed in both WF-OCTA (posterior pole/midperipheral retina) and UWFFA (posterior pole/midperipheral retina/far peripheral retina).

RESULTS

Ten consecutive patients with variable DR severity stages (17 eyes) were evaluated. Two eyes had to be excluded due to low quality of the WF-OCTA images. Therefore, 15 eyes were included for final analysis. Mean age was 57 years (± SD: 15.2) and the male : female ratio was 4 : 6. UWFFA identified retinal NP in 11 eyes (73%). Posterior pole NP was present in eight eyes, midperiphery NP was present in eight eyes, and far periphery NP was present in seven eyes. Retinal NV was detected in four eyes using UWFFA (two eyes with only midperiphery NV). WF-OCTA detected retinal NP in 11 eyes (9 cases with both posterior pole and midperiphery NP). NV was detected in three eyes (two with posterior pole and midperipheral NV, four with only midperipheral NV). Mean VD evaluated using WF-OCTA of the SCP was 0.40 (± SD: 0.1), and mean ISI in UWFFA was 0.09 (± SD: 1.3). Spearman's test did not show a significant correlation between the ISI in UWFFA and VD in WF-OCTA (p = 0.803).

CONCLUSIONS

Noninvasive WF-OCTA has great potential for the management of patients with DR. This new imaging modality might be useful in daily clinical routine in order to lower the number of invasive examinations. However, in a small percentage of patients, OCTA images cannot be reliably graded for the presence of NP and NV. In these cases, conventional FA needs to be performed.

Practical guidance for imaging biomarkers in exudative age-related macular degeneration

We provide an overview of current macular imaging techniques and identify and describe biomarkers that may be of use in the routine management of macular diseases, particularly exudative age-related macular degeneration (n-AMD). This perspective includes sections on macular imaging techniques including optical coherence tomography (OCT) and OCT angiography (OCTA), classification of exudative AMD, and biomarkers in structural OCT and OCTA. Fluorescein angiography remains a vital tool for assessing the activity of neovascular lesion, while indocyanine green angiography is the preferred option for choroidal vessels imaging in neovascular AMD. OCT provides a non-invasive three-dimensional visualization of retinal architecture in vivo and is useful in the diagnosis of many imaging biomarkers of AMD-related neovascular lesions including lesion activity. OCTA is a recent advance in OCT technology that allows accurate visualization of retinal and choroidal vascular flow. OCT and OCTA have led to an updated classification of exudative AMD lesions and provide several biomarkers that help to establish a diagnosis and the disease activity status of neovascular lesions. Individualization of therapy guided by OCT and OCTA biomarkers has the potential to further improve visual outcomes in exudative AMD. Moving forwards, integration of technologically advanced imaging equipment with AI software will help ophthalmologists to provide patients with the best possible care.

Evaluation of Subclinical Retinal Disease in Patients Affected by Systemic Lupus Erythematosus with No Evidence of Ocular Involvement-An Optical Coherence Tomography Angiography Original Study

Lupus retinopathy is the second most common eye involvement in systemic lupus erythematosus (SLE), associated with significant visual deterioration and well-known negative prognostic factor for survival. Ocular manifestation in SLE, relating the retina, ranges from asymptomatic vascular involvement to vision devastating vascular occlusions. Subclinical microvascular changes are undetectable in slit lamp examination, hence are underdiagnosed. Optical coherence tomography angiography (OCTA) is a novel, easy to interpret and non-invasive technique that allows retinal vessels visualization. OCTA simplifies clinical approach and measures the severity of decreased perfusion. The aim of the study was to demonstrate the retinal vascularization in a subclinical stage of ocular involvement in a cohort of SLE patients. Thirty-three patients (57 eyes) diagnosed with SLE were enrolled into the study group and 31 healthy individuals (56 eyes) into the control group. Vessel density reduction in parafovea, inferior and nasal quadrants of superficial retinal capillary plexus in a cohort of SLE patients was found. Among study group kidney involvement was associated with further microvasculature reduction. Knowing that retinal involvement may precede other organs impairment, early detection of retinal impairment and use of OCTA as a screening modality, may decrease overall disease morbidity.

Volume-rendered optical coherence tomography angiography during ocular interventions: Advocating for noninvasive intraoperative retinal perfusion monitoring

We aimed to test for feasibility of volume-rendered optical coherence tomography angiography (OCTA) as a novel method for assessing/quantifying retinal vasculature during ocular procedures and to explore the potential for intraoperative use. Thirty patients undergoing periocular anaesthesia were enrolled, since published evidence suggests a reduction in ocular blood flow. Retinal perfusion was monitored based on planar OCTA image-derived data provided by a standard quantification algorithm and postprocessed/volume-rendered OCTA data using a custom software script. Overall, imaging procedures were successful, yet imaging artifacts occurred frequently. In interventional eyes, perfusion parameters decreased during anaesthesia. Planar image-derived and volume rendering-derived parameters were correlated. No correlation was found between perfusion parameters and a motion artifact score developed for this study, yet all perfusion parameters correlated with signal strength as displayed by the device. Concluding, volume-rendered OCTA allows for noninvasive three-dimensional retinal vasculature assessment/quantification in challenging surgical settings and appears generally feasible for intraoperative use.

Differences in Mean Values and Variance in Quantitative Analyses of Foveal OCTA Imaging

PURPOSE

Multiple approaches for quantifying parameters such as vessel density (VD) and vessel length density (VLD) in optical coherence tomography angiography (OCTA) en-face segmentations are currently available. While it is common knowledge that data gathered from different methods should not be directly compared to each other, a comparison of the different methods can help to further the understanding of differences between different methods of measurement. Here we compare a common method of semiautomatically quantifying VD and VLD with an automated method supplied by the manufacturer of an OCTA device and report on differences in performance in order to probe for and highlight differences in values gathered by both methods.

METHODS

OCTA was performed using the swept source PLEX Elite 9000 device, software version 2.0.1.47652 (Carl Zeiss Meditec Inc., Dublin, CA, USA). Scans of 3 mm × 3 mm from healthy volunteers centred on the fovea were acquired by a well-trained certified ophthalmologist. Scans with a signal strength of 8 out of 10 or higher were included. Quantitative parameters of the 3 mm × 3 mm cube scans were automatically generated and segmented into superficial capillary plexus (SCP) and deep capillary plexus (DCP) layers using layer segmentation produced by the instrument software and prototype analysis VD quantification software (Macular Density v.0.7.1, ARI Network Hub, Carl Zeiss Meditec Inc., Dublin, CA, USA) supplied by the manufacturer. An alternative approach of quantitative analysis of VD and VLD was performed manually with ImageJ (National Institutes of Health, Bethesda, Maryland, USA), as previously reported. VD was assessed as the ratio of the retinal area occupied by vessels. VDL was measured as the total length of the skeletonised vessels using 1-pixel centre line extraction of the blood vessels.

RESULTS

We report differences in standard deviation (SD) in OCTA parameters obtained using different methods. The standard deviation of VD and VLD measurements was statistically significantly different in VD of 3 mm × 3 mm DCP (p = 0.009), VLD of 3 mm × 3 mm SCP (p = 0.000), and VLD of 3 mm × 3 mm DCP (p = 0.021). No statistically significant differences were found in VD of 3 mm × 3 mm SCP (p = 0.128) or VLD of 3 mm × 3 mm SCP (p = 0.107).

CONCLUSIONS

As expected, we were able to demonstrate significant differences in quantitative OCTA parameters gathered from the same images using different methods of quantification. Values gathered using different methods are not interchangeable. In scientific studies and in situations where long-term follow-up is necessary, the same device and the same method of quantification should be used to maintain retrospective comparability of measurements.

Reference database of total retinal vessel surface area derived from volume-rendered optical coherence tomography angiography

Optical coherence tomography angiography (OCTA) enables three-dimensional, high-resolution, depth-resolved flow to be distinguished from non-vessel tissue signals in the retina. Thus, it enables the quantification of the 3D surface area of the retinal vessel signal. Despite the widespread use of OCTA, no representative spatially rendered reference vessel surface area data are published. In this study, the OCTA vessel surface areas in 203 eyes of 107 healthy participants were measured in the 3D domain. A Generalized Linear Model (GLM) model analysis was performed to investigate the effects of sex, age, spherical equivalent, axial length, and visual acuity on the OCTA vessel surface area. The mean overall vessel surface area was 54.53 mm² (range from 27.03 to 88.7 mm²). OCTA vessel surface area was slightly negatively correlated with age. However, the GLM model analysis identified axial length as having the strongest effect on OCTA vessel surface area. No significant correlations were found for sex or between left and right eyes. This is the first study to characterize three-dimensional vascular parameters in a population based on OCTA with respect to the vessel surface area.

Exudative versus Nonexudative Age-Related Macular Degeneration: Physiopathology and Treatment Options

Age-related macular degeneration (AMD) is an eye disease typically associated with the aging and can be classified into two types—namely, the exudative and the nonexudative AMD. Currently available treatments for exudative AMD use intravitreal injections, which are associated with high risk of infection that can lead to endophthalmitis, while no successful treatments yet exist for the nonexudative form of AMD. In addition to the pharmacologic therapies administered by intravitreal injection already approved by the Food and Drug Administration (FDA) in exudative AMD, there are some laser treatments approved that can be used in combination with the pharmacological therapies. In this review, we discuss the latest developments of treatment options for AMD. Relevant literature available from 1993 was used, which included original articles and reviews available in PubMed database and also information collected from Clinical Trials Gov website using “age-related macular degeneration” and “antiangiogenic therapies” as keywords. The clinical trials search was limited to ongoing trials from 2015 to date.

Biomarkers in Early Response to Brolucizumab on Pigment Epithelium Detachment Associated with Exudative Age-Related Macular Degeneration

Background: The purpose of this study was to describe early changes in the morphology of pigment epithelium detachments (PED) after an intravitreal injection of Brolucizumab into eyes with macular neovascularization secondary to exudative age-related macular degeneration (e-AMD). Method: We included twelve eyes of 12 patients with PED secondary to e-AMD which were not responding to prior anti-VEGF treatments. An ophthalmic examination and an assessment of PED-horizontal maximal diameter (PED-HMD), PED-maximum high (PED-MH) and macular neovascularization (MNV) flow area (MNV-FA) by the means of structural optical coherence tomography (OCT) and OCT Angiography (OCT-A) were performed at baseline, as well as 1, 7, 14 and 30 days after the injection. Results: The mean age of the population of study was 78.4 (SD ± 4.8). The mean number of previous Ranibizumab or Aflibercept injections was 13 (SD ± 8). At the last follow-up visit, the PED-HMD did not significantly change (p = 0.16; F(DF:1.94, 20,85) = 1.9), the PED-MH showed a significant reduction [p = 0.01; F(DF:1.31, 14.13) = 6.84.] and the MNV-FA did not significantly differ (p = 0.1; F(1.97, 21.67) = 2.54) from baseline. No signs of ocular inflammation were observed during follow-up. Conclusions: A single Brolucizumab injection was able to determine the short-term effects on PEDs’ anatomical features of eyes with an unresponsive e-AMD.

Clinical Utility of Artificial Intelligence Algorithms to Enhance Wide-Field Optical Coherence Tomography Angiography Images

The aim of this paper is to investigate the clinical utility of the application of deep learning denoise algorithms on standard wide-field Optical Coherence Tomography Angiography (OCT-A) images. This was a retrospective case-series assessing forty-nine 10 × 10 mm OCT-A1 macula scans of 49 consecutive patients attending a medical retina clinic over a 6-month period. Thirty-seven patients had pathology; 13 had none. Retinal vascular layers were categorised into superficial or deep capillary plexus. For each category, the retinal experts compared the original standard image with the same image that had intelligent denoise applied. When analysing the Superficial Capillary Plexus (SCP), the denoised image was selected as "best for clinical assessment" in 98% of comparisons. No difference was established in the remaining 2%. On evaluating the Deep Capillary Plexus (DCP), the denoised image was preferred in 35% of comparisons. No difference was found in 65%. There was no evidence of new artefactual features nor loss of anatomical detail in denoised compared to the standard images. The wide-field denoise feature of the Canon Xephilio OCT-A1 produced scans that were clinically preferable over their original OCT-A images, especially for SCP assessment, without evidence for causing a new artefactual error.

Retinal vascular metrics difference by comparison of two image acquisition modes using a novel OCT angiography prototype

PURPOSE

To assess the different impact of two enface OCTA image simultaneously acquired by means of a new prototype of Spectral-Domain Optical Coherence Tomography Angiography (SD-OCTA) on quantitative retinal vascular metrics.

METHODS

In this prospective observational cross-sectional study 28 healthy subjects were enrolled. Macular (3x3 mm) OCTA images were acquired for all participants using Solix Fullrange OCT (Optovue Inc, Freemont CA, USA). The main outcome measurements were: Perfusion density (PD), vessel length density (VLD), and vessel diameter index (VDI) of both superficial capillary plexus (SCP) and deep capillary plexus (DCP), and choriocapillaris (CC) total flow-deficits area. Quantitative retinal vascular metrics were measured on binarized and skeletonized OCTA images by comparing not averaged and fast automated multiple averaged en face OCTA images.

RESULTS

In both SCP and DCP, PD significantly increased (p = 0,005 and p = 0,030, respectively), and VLD significantly decreased (p<0,001 and p = 0,004, respectively), and VDI increased (p<0,001 and p = 0,068, respectively), and total CC flow deficits area significantly decreased (p<0,001) by averaging multiple OCTA images.

CONCLUSIONS

In this study, we found a significant difference of quantitative retinal metrics by comparing two different image acquisition modes using a novel and fully automated averaging OCTA system in young healthy subjects.

Morphologic analysis of macular neovascularizations by OCT angiography-Technical limitations in the comparison of 3×3mm and 6×6mm images

Background

The aim of this study was to ascertain whether there are relevant differences between the vascular morphology of macular neovascularizations (MNV) in 3×3mm and 6×6mm images, produced by optical coherence tomography angiography (OCTA).

Methods

MNV of 49 patients were automated quantitative analysed, measuring area, flow, the fractal dimension, average vessel length, vascular density, and average vessel caliber. These parameters were compared between the 3×3mm and the 6×6mm images.

Results

A strong linear association was found between the 3×3mm and the 6×6mm images. While area, flow, and FD of the MNV were very similar, the 3×3mm images showed significantly lower average total vessel length, greater vascular density, and lower average vessel caliber.

Conclusion

In quantitative analysis of the morphologic parameters of MNV in 3×3mm and 6×6mm images, the structures are not directly equivalent in the two sizes of scan. The images must be evaluated on an individual basis.