Optical Coherence Tomography Angiography Compared With Optical Coherence Tomography Macular Measurements for Detection of Glaucoma

The Role of Optical Coherence Tomography Angiography in Glaucoma

Glaucoma is the leading cause of irreversible vision loss and comprises a group of chronic optic neuropathies characterized by progressive retinal ganglion cell (RGC) loss. Various etiologies, including impaired blood supply to the optic nerve, have been implicated for glaucoma pathogenesis. Optical coherence tomography angiography (OCTA) is a non-invasive imaging modality for visualizing the ophthalmic microvasculature. Using blood flow as an intrinsic contrast agent, it distinguishes blood vessels from the surrounding tissue. Vessel density (VD) is mainly used as a metric for quantifying the ophthalmic microvasculature. The key anatomic regions for OCTA in glaucoma are the optic nerve head area including the peripapillary region, and the macular region. Specifically, VD of the superficial peripapillary and superficial macular microvasculature is reduced in glaucoma patients compared to unaffected subjects, and VD correlates with functional deficits measured by visual field (VF). This renders OCTA similar in diagnostic capabilities compared to structural retinal nerve fiber layer (RNFL) thickness measurements, especially in early glaucoma. Furthermore, in cases where RNFL thickness measurements are limited due to artifact or floor effect, OCTA technology can be used to evaluate and monitor glaucoma, such as in eyes with high myopia and eyes with advanced glaucoma. However, the clinical utility of OCTA in glaucoma management is limited due to the prevalence of imaging artifacts. Overall, OCTA can play a complementary role in structural OCT imaging and VF testing to aid in the diagnosis and monitoring of glaucoma.

Racial Differences in the Diagnostic Accuracy of OCT Angiography Macular Vessel Density for Glaucoma

PURPOSE

To evaluate and compare the diagnostic accuracy of macular vessel density (VD) measured by OCT angiography (OCTA) in individuals of African descent (AD) and European descent (ED) with open-angle glaucoma.

DESIGN

Observational, cross sectional study.

PARTICIPANTS

A total of 176 eyes of 123 patients with glaucoma and 140 eyes of 88 healthy participants from the Diagnostic Innovations in Glaucoma Study.

METHODS

Whole-image ganglion cell complex (wiGCC) thickness and macular VD (parafoveal VD and perifoveal VD) were obtained from 6 × 6 macula scans. Area under the receiver operating characteristic (AUROC) curves were used to evaluate the diagnostic accuracy of macular VD and ganglion cell complex (GCC) thickness in AD and ED participants after adjusting for confounders such as age, visual field mean deviation (VF MD), signal strength index, axial length, self-reported hypertension and diabetes.

MAIN OUTCOME MEASURES

Macular VD and wiGCC measurements.

RESULTS

Parafoveal and perifoveal VD were significantly lower in ED than AD patients with glaucoma. Parafoveal and perifoveal VD performed significantly worse in AD participants compared with ED participants for detection of glaucoma (adjusted AUROC, 0.75 [95% confidence interval (CI), 0.62, 0.87], 0.85 [95% CI, 0.79, 0.90], P = 0.035; and 0.82 [95% CI, 0.70, 0.92], 0.91 [95% CI, 0.87, 0.94], respectively; P = 0.020). In contrast to VD, diagnostic accuracy of GCC thickness was similar in AD and ED individuals (adjusted AUROC, 0.89 [95% CI, 0.79, 0.96], 0.92 [95% CI, 0.86, 0.96], respectively; P = 0.313). The diagnostic accuracies of both macular VD and GCC thickness for differentiating between glaucoma and healthy eyes increased with increasing VF MD in both AD and ED participants.

CONCLUSIONS

Diagnostic performance of OCTA macular VD, but not GCC thickness, for glaucoma detection varies by race. Moreover, macular VD parameters had lower accuracy for detecting glaucoma in AD individuals than in ED individuals. The diagnostic performance of macular VD is race-dependent, and, therefore, race should be taken into consideration when interpreting macular OCTA results.

FINANCIAL DISCLOSURE(S)

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

Endpoints for clinical trials in ophthalmology

With the identification of novel targets, the number of interventional clinical trials in ophthalmology has increased. Visual acuity has for a long time been considered the gold standard endpoint for clinical trials, but in the recent years it became evident that other endpoints are required for many indications including geographic atrophy and inherited retinal disease. In glaucoma the currently available drugs were approved based on their IOP lowering capacity. Some recent findings do, however, indicate that at the same level of IOP reduction, not all drugs have the same effect on visual field progression. For neuroprotection trials in glaucoma, novel surrogate endpoints are required, which may either include functional or structural parameters or a combination of both. A number of potential surrogate endpoints for ophthalmology clinical trials have been identified, but their validation is complicated and requires solid scientific evidence. In this article we summarize candidates for clinical endpoints in ophthalmology with a focus on retinal disease and glaucoma. Functional and structural biomarkers, as well as quality of life measures are discussed, and their potential to serve as endpoints in pivotal trials is critically evaluated.

Neurovascular dysfunction in glaucoma

Retinal ganglion cells, the neurons that die in glaucoma, are endowed with a high metabolism requiring optimal provision of oxygen and nutrients to sustain their activity. The timely regulation of blood flow is, therefore, essential to supply firing neurons in active areas with the oxygen and glucose they need for energy. Many glaucoma patients suffer from vascular deficits including reduced blood flow, impaired autoregulation, neurovascular coupling dysfunction, and blood-retina/brain-barrier breakdown. These processes are tightly regulated by a community of cells known as the neurovascular unit comprising neurons, endothelial cells, pericytes, Müller cells, astrocytes, and microglia. In this review, the neurovascular unit takes center stage as we examine the ability of its members to regulate neurovascular interactions and how their function might be altered during glaucomatous stress. Pericytes receive special attention based on recent data demonstrating their key role in the regulation of neurovascular coupling in physiological and pathological conditions. Of particular interest is the discovery and characterization of tunneling nanotubes, thin actin-based conduits that connect distal pericytes, which play essential roles in the complex spatial and temporal distribution of blood within the retinal capillary network. We discuss cellular and molecular mechanisms of neurovascular interactions and their pathophysiological implications, while highlighting opportunities to develop strategies for vascular protection and regeneration to improve functional outcomes in glaucoma.

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/ .

Automatic segmentation of multitype retinal fluid from optical coherence tomography images using semisupervised deep learning network

BACKGROUND/AIMS

To develop and validate a deep learning model for automated segmentation of multitype retinal fluid using optical coherence tomography (OCT) images.

METHODS

We retrospectively collected a total of 2814 completely anonymised OCT images with subretinal fluid (SRF) and intraretinal fluid (IRF) from 141 patients between July 2018 and June 2020, constituting our in-house retinal OCT dataset. On this dataset, we developed a novel semisupervised retinal fluid segmentation deep network (Ref-Net) to automatically identify SRF and IRF in a coarse-to-refine fashion. We performed quantitative and qualitative analyses on the model's performance while verifying its generalisation ability by using our in-house retinal OCT dataset for training and an unseen Kermany dataset for testing. We also determined the importance of major components in the semisupervised Ref-Net through extensive ablation. The main outcome measures were Dice similarity coefficient (Dice), sensitivity (Sen), specificity (Spe) and mean absolute error (MAE).

RESULTS

Our model trained on a handful of labelled OCT images manifested higher performance (Dice: 81.2%, Sen: 87.3%, Spe: 98.8% and MAE: 1.1% for SRF; Dice: 78.0%, Sen: 83.6%, Spe: 99.3% and MAE: 0.5% for IRF) over most cutting-edge segmentation models. It obtained expert-level performance with only 80 labelled OCT images and even exceeded two out of three ophthalmologists with 160 labelled OCT images. Its satisfactory generalisation capability across an unseen dataset was also demonstrated.

CONCLUSION

The semisupervised Ref-Net required only la few labelled OCT images to generate outstanding performance in automate segmentation of multitype retinal fluid, which has the potential for providing assistance for clinicians in the management of ocular disease.

The Effect of Myopia on Vessel Density in Glaucomatous Patients by Optical Coherence Tomography Angiography

Background

Glaucoma is a degenerative optic neuropathy that causes anatomical and functional visual impairment.

Aim and Objectives

This investigation's primary goal was to perform a qualitative and quantitative assessment of macular and peripapillary vessels to detect the impairment of blood flow in glaucomatous patients with or without myopia which can affect the prognosis of glaucoma and visual field.

Subjects and Methods

This prospective, cross-sectional, observational research was performed for glaucomatous patients with and without myopia who attend the outpatient clinic at the ophthalmology department, at Benha University. The study was conducted on 50 subjects with glaucomatous eyes, divided into two groups: the first group consisted of (25 subjects) of glaucoma with myopia and the second group (25 subjects) of glaucoma with the same severity of mean deviation in the visual field of group 1 without myopia, using OCTA to measure retinal vessel density (superficial vessel density) and OCT thickness ILM-RPE, RNFL thickness, GCL and small vessel density (RADIAL PERI PAPILLARY PLEXUS).

Results

Regarding demographic data of myopia in the studied eyes, there were (9) 18% with low myopia with no significance, (32) 64% with moderate myopia, and (9) 18% with high myopia, with open-angle glaucoma patients showed a highly significant decline in total retinal nerve fiber layer thickness, superior-nasal RNFL thickness, Inferior-nasal RNFL thickness, superior-temporal RNFL and inferior-temporal RNFL thickness compared to open-angle glaucoma patients without myopia.

Conclusion

Our results show that microvascular attenuation occurs more significantly in OAG than in myopia. When both myopia and OAG are present, there is a higher reduction in microvascular attenuation than with either disease alone. The development and progression of glaucoma in individuals with high myopia are more aggressive than in low or non-myopia, so by using OCTA detection of early microvascular changes in high myopia, individuals help the early detection and management of glaucoma.

Evaluation of the Glaucomatous Macular Damage by Chromatic Pupillometry

INTRODUCTION

This study aimed to examine the performance of binocular chromatic pupillometry for the objective and rapid detection of primary open-angle glaucoma (POAG), and to explore the association between pupillary light response (PLR) features and structural glaucomatous macular damage.

METHODS

Forty-six patients (mean age 41.00 ± 13.03 years) with POAG and 23 healthy controls (mean age 42.00 ± 11.08 years) were enrolled. All participants underwent sequenced PLR tests of full-field, superior/inferior quadrant-field chromatic stimuli using a binocular head-mounted pupillometer. The constricting amplitude, velocity, and time to max constriction/dilation, and the post-illumination pupil response (PIPR) were analyzed. The inner retina thickness and volume measurements were determined by spectral domain optical coherence tomography.

RESULTS

In the full-field stimulus experiment, time to pupil dilation was inversely correlated with perifoveal thickness (r = - 0.429, P < 0.001) and perifoveal volume (r = - 0.364, P < 0.001). Dilation time (AUC 0.833) showed good diagnostic performance, followed by the constriction amplitude (AUC 0.681) and PIPR (AUC 0.620). In the superior quadrant-field stimulus experiment, time of pupil dilation negatively correlated with inferior perifoveal thickness (r = - 0.451, P < 0.001) and inferior perifoveal volume (r = - 0.417, P < 0.001). The dilation time in response to the superior quadrant-field stimulus showed the best diagnostic performance (AUC 0.909). In the inferior quadrant-field stimulus experiment, time to pupil dilation (P < 0.001) correlated well with superior perifoveal thickness (r = - 0.299, P < 0.001) and superior perifoveal volume (r = - 0.304, P < 0.001).

CONCLUSION

The use of chromatic pupillometry offers a patient-friendly and objective approach to detect POAG, while the impairment of PLR features may serve as a potential indicator of structural macular damage.

Diagnostic Accuracy of Imaging Devices in Glaucoma: An Updated Meta-Analysis

Background

Different devices have diverse accuracy in diagnosing glaucoma, and therefore choosing the best device is challenging. Thereby, this study was conducted to evaluate the diagnostic sensitivity and specificity of imaging devices in glaucoma and explore the need for an updated meta-analysis on this issue.

Methods

In this systematic review and meta-analysis, PubMed, Scopus, and Web of Science databases were searched for articles published between January 2004 and 2022. Cross-sectional or diagnostic studies were selected, and sensitivity, specificity, positive predictive value, and negative predictive value were measured.

Results

A total of 28 cross-sectional studies were included for meta-analysis. Devices were divided into 2 groups, based on the optic nerve area and the macular area. For the nerve area, the pooled sensitivity was 77% (CI 95%, 70-83; I2, 90.01%) and the pooled specificity was 89% (CI 95%, 84-92, I2, 93.22%), and for the macular area, the pooled sensitivity was 87% (CI 95%, 80-92, I2, 91.79%), and the pooled specificity was 90% (CI 95%, 84-94; I2, 86.30%). We analyzed each device separately. For optical coherence tomography(OCT), the pooled sensitivity was 85% (CI 95%, 81-89; I2, 87.82%) and the pooled specificity was 89% (CI 95%, 85-92; I2, 84.39%); for Heidelberg retinal tomography (HRT), the pooled sensitivity was 72% (CI 95%, 57-83; I2, 88.94%) and the pooled specificity was 79% (CI 95%, 62-90; I2, 98.61%), and for optical coherence tomography angiography (OCTA), the pooled sensitivity was 82% (CI 95%, 66-91; I2, 93.71%) and the pooled specificity was 93% (CI 95%, 87-96; I2, 64.72%).

Conclusion

The macular area was more sensitive and specific than the optic nerve head. Furthermore, OCT had higher sensitivity, and OCTA had higher specificity when compared with other imaging devices.

Diagnostic ability of macular microvasculature with swept-source OCT angiography for highly myopic glaucoma using deep learning

Macular OCT angiography (OCTA) measurements have been reported to be useful for glaucoma diagnostics. However, research on highly myopic glaucoma is lacking, and the diagnostic value of macular OCTA measurements versus OCT parameters remains inconclusive. We aimed to evaluate the diagnostic ability of the macular microvasculature assessed with OCTA for highly myopic glaucoma and to compare it with that of macular thickness parameters, using deep learning (DL). A DL model was trained, validated and tested using 260 pairs of macular OCTA and OCT images from 260 eyes (203 eyes with highly myopic glaucoma, 57 eyes with healthy high myopia). The DL model achieved an AUC of 0.946 with the OCTA superficial capillary plexus (SCP) images, which was comparable to that with the OCT GCL+ (ganglion cell layer + inner plexiform layer; AUC, 0.982; P = 0.268) or OCT GCL++ (retinal nerve fiber layer + ganglion cell layer + inner plexiform layer) images (AUC, 0.997; P = 0.101), and significantly superior to that with the OCTA deep capillary plexus images (AUC, 0.779; P = 0.028). The DL model with macular OCTA SCP images demonstrated excellent and comparable diagnostic ability to that with macular OCT images in highly myopic glaucoma, which suggests macular OCTA microvasculature could serve as a potential biomarker for glaucoma diagnosis in high myopia.

Evaluation of vessel density in healthy subjects with family history of glaucoma

OBJECTIVES

To investigate whether any microvascular changes are present in optic disc, peripapillary or maculary regions in healthy subjects with a family history of glaucoma.

METHODS

A total of 82 healthy subjects including 42 first-degree relatives of primary open-angle glaucoma (POAG) and 40 controls were enroled in this cross-sectional study. Global and sectoral vessel density (VD) measurements excluding large vessels, retina nerve fibre layer (RNFL) and macula ganglion cell (mGCC) thicknesses were obtained from a combined optical coherence tomography-angiography (OCT-A) and spectral-domain OCT system. Effect size (ES) was used for evaluating the magnitude of the statistically significant difference. Area under receiver operating characteristic curves (AUCs) were used to examine the ability of parameters to differentiate first-degree relatives to controls.

RESULTS

There was no significant difference in RNFL and mGCC thicknesses between groups. Although lower VD measurements in optic disc, peripapillary region, and macula were observed in the first-degree relatives, statistically significant mean difference (3.13 ± 0.87, p = 0.001) and large ES (0.80) were in only lower nasal sector of peripapillary region. Inter-eye asymmetry of supero-nasal VD was also statistically higher (3.74 ± 2.55 vs 1.89 ± 1.64) with a large ES in the first-degree relatives (p < 0.001, ES = 0.86). AUC for differentiating first-degree relatives from controls was highest for inter-eye asymmetry of supero-nasal sector VD (0.74, p < 0.001), followed by lower nasal sector VD (0.72, p < 0.001).

CONCLUSION

Compared to controls, first-degree relatives of patients with POAG were found to have significantly greater inter-eye asymmetry in supero-nasal peripapillary VD and less VD in the lower nasal peripapillary region.

The role of optical coherence tomography angiography in moderate and advanced primary open-angle glaucoma

PURPOSE

To evaluate the relationship between structure and function in moderate and advanced primary open-angle glaucoma (POAG) and to determine the accuracy of structure and vasculature for discriminating moderate from advanced POAG.

METHODS

In this cross-sectional study, 25 eyes with moderate and 40 eyes with advanced POAG were enrolled. All eyes underwent measurement of the thickness of circumpapillary retinal nerve fiber layer (cpRNFL) and macular ganglion cell complex (GCC), and optical coherence tomography angiography (OCTA) of the optic nerve head (ONH) and macula. Visual field (VF) was evaluated by Swedish interactive threshold algorithm and 24-2 and 10-2 patterns. The correlation between structure and vasculature and the mean deviation (MD) of the VFs was evaluated by a partial correlation coefficient. The area under the receiver operating characteristic curve (AUC) was applied for assessing the power of variables for discrimination moderate from advanced POAG.

RESULTS

Including all eyes, whole image vessel density (wiVD) of the ONH area, and vessel density (VD) in the inferior quadrant of perifovea were the parameters with significant correlation with the mean deviation (MD) of the VF 24-2 in OCTA of the ONH and macula (r = .649 and .397; p < .05). The greatest AUCs for discriminating moderate and advanced POAG belonged to VD of the inferior hemifield of ONH area (.886; 95% CI (.805, .967)), and VD in the inferior quadrant of perifovea (.833; 95% CI (.736, .930)) without statistically significant difference (.886 Versus .833; p = .601).

CONCLUSION

Among vascular parameters of the ONH area, wiVD had the strongest correlation with the MD of the VF 24-2 while VD of the inferior hemifield of the ONH area had the greatest AUC for discriminating moderate and advanced POAG. Vessel density in the inferior quadrant of perifovea had a significant correlation with the MD of VF 24-2 and also the greatest AUC for discriminating moderate and advanced POAG.

Macular Thickness and Microvasculature Loss in Glaucoma Suspect Eyes

PURPOSE

To characterize the change of ganglion cell complex (GCC) thickness and macular vessel density in glaucoma suspect eyes with ocular hypertension (OHT) or glaucomatous optic neuropathy (GON).

DESIGN

Prospective, longitudinal study.

PARTICIPANTS

Eight-three eyes (24 healthy, 30 OHT, and 29 GON) of 65 patients who underwent at least 3 visits were included from the Diagnostic Innovations in Glaucoma Study. The mean follow-up was at least 3 years.

METHODS

OCT angiography (OCTA)-based vessel density and OCT-based structural thickness of the 3 × 3-mm¹ GCC scan slab were evaluated at each visit. The rates of vessel density and thickness change were compared across diagnostic groups using a linear mixed-effects model.

MAIN OUTCOME MEASURES

Change rates of macula GCC thickness and superficial vessel density.

RESULTS

Significant mean rates of both GCC thinning and vessel density loss were detectable in OHT and GON groups. Of the individual suspect eyes, 49.1% showed significant loss (P < 0.05) with either vessel density or GCC thickness. Of the GON eyes, 31.0% showed both significant GCC loss and vessel density loss, 51.7% showed only significant GCC loss, whereas 17.2% showed only significant vessel density loss. Vessel density loss was faster than GCC thinning in half of the suspect eyes based on percent loss analysis. The age and scan quality-adjusted GCC thinning rates of the OHT group (-0.59 μm/year; P = 0.025) and GON group (-0.79 μm/year; P = 0.058) were faster than those of the healthy group (-0.11 μm/year), whereas the rate of vessel density loss was not significantly different among the diagnostic groups (all P > 0.2). Higher mean intraocular pressure during follow-up was associated with faster GCC thinning in the OHT group (P = 0.065) and GON groups (P = 0.015), but was not associated with the rate of vessel density decrease.

CONCLUSIONS

Whereas the rate of GCC thinning was faster on average in suspect eyes than in healthy eyes, some suspect eyes showed significant loss of vessel density and faster vessel density loss than GCC thinning. OCT and OCTA are complementary and useful for evaluating eyes with OHT or GON.

Relationship between macular intercapillary area measured by optical coherence tomography angiography and central visual field sensitivity in normal tension glaucoma

PURPOSE

To investigate the relationship of macular intercapillary area (ICA) with macular ganglion cell-inner plexiform layer (GCIPL) thickness and central visual field sensitivity (CVFS) in normal tension glaucoma (NTG).

METHODS

Seventy-eight early NTG eyes, 33 moderate-to-severe NTG eyes and 75 normal control eyes were cross-sectional evaluated. All participants underwent swept-source optical coherence tomography angiography (OCT-A; DRI-OCT, Topcon, Tokyo, Japan). A customised MATLAB program was used to quantify macular OCT-A metrics at central 3×3 mm macular region including vascular density (VD), foveal avascular zone (FAZ) area, 10 largest ICA including FAZ area (ICA10_IncFAZ) and excluding FAZ area (ICA10_ExcFAZ). Generalised estimating equation regression models were performed to determine the relationships of OCT-A vascular metrics with GCIPL thickness in the macular region and CVFS.

RESULTS

NTG eyes had lower global VD, larger ICA10_IncFAZ, and larger ICA10_ExcFAZ than normal controls (all p≤0.016). In the multivariable analyses, decreased VD (β=-0.304, p=0.006) and increased ICA (β=-0.231 for ICA10_IncFAZ and β=-0.259 for ICA10_ExcFAZ, all p≤0.042) were significantly associated with decreased GCIPL thickness in early NTG eyes but not in moderate-to-severe NTG eyes. ICA enlargement was associated with CVFS in early NTG eyes (β=-0.310, p=0.009), while VD was associated with CVFS in moderate-to-severe NTG eyes (β=-0.272, p=0.038).

CONCLUSION

ICA enlargement could be a potentially important disease marker of early NTG as reflected by its association with GCIPL thinning and decrease CVFS specifically for early NTG eyes.

Assessment of Artifacts in Swept-Source Optical Coherence Tomography Angiography for Glaucomatous and Normal Eyes

Purpose

To evaluate the frequency of and identify the factors that influence the artifacts of swept-source optical coherence tomography angiography (SS-OCTA) in glaucomatous and normal eyes.

Methods

Artifacts of OCTA images of open-angle glaucoma (OAG) and normal subjects were analyzed using SS-OCTA. Univariate and multivariate logistic regression analyses were performed to evaluate the association of age, sex, best-corrected visual acuity, axial length (AL), intraocular pressure, presence and severity of OAG, and image quality score (IQS) with the presence of artifacts.

Results

Images from 4426 subjects were included in the study. At least one type of artifact was present in 24.54% of the images. The most common artifacts were occurrence of motion (705 eyes, 15.93%), followed by defocus (628 eyes, 14.19%), decentration (134 eyes, 3.03%), masking (62 eyes,1.40%), and segmentation errors (23 eyes, 0.52%). Multivariate logistic analyses showed that the presence of OAG (odds ratio [OR] = 2.71; 95% confidence interval [CI], 2.09-3.51; P < 0.001), female sex (OR = 1.34; 95% CI, 1.12-1.61; P = 0.001), longer AL (OR = 1.09; 95% CI, 1.02-1.17; P = 0.017), and IQS < 40 (OR = 3.75; 95% CI, 3.15-4.48; P < 0.001) were significantly associated with higher odds for the presence of any artifact. The IQS had poor performance for detecting artifacts, with an area under the curve of 0.723, sensitivity of 73.04%, and specificity of 62.53%.

Conclusions

OAG eyes had more SS-OCTA image artifacts than normal eyes. IQS is an imperfect tool for identifying artifacts.

Translational Relevance

Special attention should be paid to the effect of artifacts when using SS-OCTA in the clinical setting to assess vascular parameters in patients with glaucoma.

Combining Structural and Vascular Parameters to Discriminate Among Glaucoma Patients, Glaucoma Suspects, and Healthy Subjects

Purpose

Compare the ability of peripapillary and macular structural parameters, vascular parameters, and their integration to discriminate among glaucoma, suspected glaucoma (GS), and healthy controls (HCs).

Methods

In this study, 196 eyes of 119 patients with glaucoma (n = 81), patients with GS (n = 48), and HCs (n = 67) underwent optical coherence tomography (OCT) and OCT angiography to measure peripapillary retinal nerve fiber layer (pRNFL), macular ganglion cell-inner plexiform layer (mGCIPL) thicknesses, radial peripapillary capillary perfusion density (RPC-PD), and macular GCIPL perfusion density (GCIPL-PD). Parameters were integrated regionally with logistic regression and globally with machine learning algorithms. Diagnostic performances were evaluated with area under the receiver operating characteristic (AUROC) curves.

Results

Patients with glaucoma had mild to moderate damage (median, -3.3 dB; interquartile range, -6.5 to -1.4). In discriminating between patients with glaucoma and the HCs, pRNFL thickness had higher AUROC curve values than RPC-PD for average (0.87 vs. 0.62; P < 0.001), superior (0.86 vs. 0.54; P < 0.001), inferior (0.90 vs. 0.71; P < 0.001), and temporal (0.65 vs. 0.51; P = 0.02) quadrants. mGCIPL thickness had higher AUROC curve values than GCIPL-PD for average (0.84 vs. 0.68; P < 0.001), superotemporal (0.76 vs. 0.65; P = 0.016), superior (0.72 vs. 0.57; P = 0.004), superonasal (0.70 vs. 0.56; P = 0.01), inferotemporal (0.90 vs. 0.72; P < 0.001), inferior (0.87 vs. 0.69; P < 0.001), and inferonasal (0.78 vs. 0.65, P = 0.012) sectors. All structural multisector indices had higher diagnostic ability than vascular ones (P < 0.001). Combined structural-vascular indices did not outperform structural indices. Similar results were found to discriminate glaucoma from GS.

Conclusions

Combining structural and vascular parameters in a structural-vascular index does not improve diagnostic ability over structural parameters alone.

Translational Relevance

OCT angiography does not add additional benefit to structural OCT in early to moderate glaucoma diagnosis.

Loss of Caveolin-1 Impairs Light Flicker-Induced Neurovascular Coupling at the Optic Nerve Head

Glaucoma is a neurodegenerative disease, which results in characteristic visual field defects. Intraocular pressure (IOP) remains the main risk factor for this leading cause of blindness. Recent studies suggest that disturbances in neurovascular coupling (NVC) may be associated with glaucoma. The resultant imbalance between vascular perfusion and neuronal stimulation in the eye may precede retinal ganglion cell (RGC) loss and increase the susceptibility of the eye to raised IOP and glaucomatous degeneration. Caveolin-1 (Cav-1) is an integral scaffolding membrane protein found abundantly in retinal glial and vascular tissues, with possible involvement in regulating the neurovascular coupling response. Mutations in Cav-1 have been identified as a major genetic risk factor for glaucoma. Therefore, we aim to evaluate the effects of Cav-1 depletion on neurovascular coupling, retinal vessel characteristics, RGC density and the positive scotopic threshold response (pSTR) in Cav-1 knockout (KO) versus wild type C57/Bl6 mice (WT). Following light flicker stimulation of the retina, Cav-1 KO mice showed a smaller increase in perfusion at the optic nerve head and peripapillary arteries, suggesting defective neurovascular coupling. Evaluation of the superficial capillary plexus in Cav-1 KO mice also revealed significant differences in vascular morphology with higher vessel density, junction density and decreased average vessel length. Cav-1 KO mice exhibited higher IOP and lower pSTR amplitude. However, there was no significant difference in RGC density between Cav-1 KO and wild type mice. These findings highlight the role of Cav-1 in regulating neurovascular coupling and IOP and suggest that the loss of Cav-1 may predispose to vascular dysfunction and decreased RGC signaling in the absence of structural loss. Current treatment for glaucoma relies heavily on IOP-lowering drugs, however, there is an immense potential for new therapeutic strategies that increase Cav-1 expression or augment its downstream signaling in order to avert vascular dysfunction and glaucomatous change.

Vessel Density in the Macular and Peripapillary Areas in Preperimetric Glaucoma to Various Stages of Primary Open-Angle Glaucoma in Taiwan

Peripapillary and macular vessel density (VD) are reduced in myopic non-glaucomatous eyes, the dynamic range of VD may be decreased by myopia, and whether VD measurement has the potential in differentiating stages of glaucoma severity in patients with myopic glaucoma remains questionable. This observational, cross-sectional study aimed to clarify the changes in peripapillary and macular VDs in preperimetric glaucoma (PPG) and primary open-angle glaucoma in the early, moderate, and late stages. A total of 1228 eyes from 661 participants (540 normal, 67 PPG, and 521 glaucomatous) were included. Participants underwent free blood tests at the internal medicine clinic to retrieve systemic data. Patients with glaucoma were grouped by disease severity, defined by glaucomatous visual field mean defect, including early-(224 eyes), moderate-(103 eyes), and late-stage glaucoma (194 eyes), and further divided into advanced (158 eyes) and terminal glaucoma (36 eyes). Macular VD, peripapillary VD, circumpapillary retinal nerve fiber layer (cpRNFL) thickness, and ganglion cell complex (GCC) thickness were evaluated and divided into superior and inferior parts. One-way analysis of variance was performed, followed by Tukey’s post-hoc test. The peripapillary VD was significantly different between the healthy and PPG groups and the early-, moderate-, and late-stage glaucoma subgroups (all p < 0.001). Peripapillary VD measurements are helpful in differentiating the various stages of glaucoma even in patients with myopic glaucoma.

Combined wide-field optical coherence tomography angiography density map for high myopic glaucoma detection

The present study aimed to evaluate the diagnostic ability of wide-field optical coherence tomography angiography (OCTA) density map for detection of glaucomatous damage in high myopic (HM) eyes and to further compare the diagnostic ability of OCTA with that of conventional imaging approaches including red-free photography and swept-source OCT (SS-OCT) wide-field maps. A total of 77 healthy HM eyes and 72 HM eyes with open angle glaucoma (OAG) participated in this retrospective observational study. Patients underwent a comprehensive ocular examination, including wide-field SS-OCT scan and peripapillary area and macular OCTA scans. An integrated OCTA density map thereafter was merged by vascular landmark-guided superimposition of peripapillary and macular superficial vascular density maps onto the red-free photography (resulting in the OCTA-PanoMap). Glaucoma specialists then determined the presence of glaucomatous damage in HM eyes by reading the OCTA-PanoMap and compared its sensitivity and specificity with those of conventional images. Sensitivity and specificity of OCTA-PanoMap for HM-OAG diagnosis was 94.4% and 96.1%, respectively. Compared with other imaging methods, the sensitivity of OCTA-PanoMap was significantly higher than that of red-free photography (P = 0.022) and comparable to that of wide-field SS-OCT maps. Specificity of OCTA-PanoMap was significantly higher than those of other conventional imaging methods (except for wide-field thickness map). The OCTA-PanoMap showed good diagnostic ability for discrimination of HM-OAG eyes from healthy HM eyes. As a complementary method of an alternative imaging modality, OCTA-PanoMap can be a useful tool for detection of HM-OAG.

Optical coherence tomography angiography in primary eye care

Optical coherence tomography angiography (OCT-A) is a non-invasive imaging modality for assessing the vasculature within ocular structures including the retina, macula, choroid and optic nerve. OCT-A has a wide range of clinical applications in various optometric conditions which have been independently reported in the literature. This paper aims to present a review of the current literature on the clinical application of OCT-A in optometric practice as well as to analyse and evaluate the quality of the available evidence. This review included 78 articles from a literature search conducted on 26 May 2019 across the following databases: Cochrane Library of Systematic Reviews, Medline, Scopus and Web of Science. Primary ocular pathologies discussed in this review include glaucoma, diabetic retinopathy, age-related macular degeneration, myopia, acquired and congenital macular dystrophies, epiretinal membrane, retinal vein occlusion, retinitis pigmentosa, choroidal melanoma, uveitis, central serous chorioretinopathy, amblyopia and optic neuropathies. Primary outcome variables included vessel density, foveal avascular zone area and diameter, flow velocity and flow index. This review aims to evaluate the evidence available for OCT-A applications in diagnosis and prognosis of ocular conditions in an optometric setting.

Progression of Parapapillary Choroidal Microvascular Dropout After Disc Hemorrhage in Glaucoma Patients: 2 Case Reports

PURPOSE

Microvasculature dropout (MvD) is a novel finding seen in optical coherence tomography angiography (OCTA), which is characterized by a localized dehiscence of the choriocapillaris in the parapapillary atrophy area. Disc hemorrhage (DH) is an important factor often associated with the development and especially progression of glaucoma. Here, we present 2 cases of MvD progression with DH.

METHODS AND RESULTS

Case 1: A 62-year-old female patient with normal tension glaucoma in both her eyes had recurrent DH at the inferior area of her right eye. A new DH was observed in the inferotemporal area of the right eye with MvD progression on OCTA in the same direction three months from the baseline.Case 2: A 57-year-old female patient with bilateral steroid-induced secondary glaucoma also had recurrent DH in her right eye. Four months from the baseline, DH occurred in the superotemporal and inferotemporal area of the right eye, and MvD was detected on OCTA in the superotemporal corresponding direction. After 19 months from the baseline, OCTA was repeated. The DH had resolved, but the superotemporal MvD persisted.

CONCLUSIONS

The 2 cases presented here are the first to report on the relationship between MvD progression and DH. MvD as visualized in OCTA imaging looks to be of clinical importance, and hopefully future studies will reveal the actual connection between MvD, DH, and glaucoma progression.

Optical Coherence Tomography and Glaucoma

Early detection and monitoring are critical to the diagnosis and management of glaucoma, a progressive optic neuropathy that causes irreversible blindness. Optical coherence tomography (OCT) has become a commonly utilized imaging modality that aids in the detection and monitoring of structural glaucomatous damage. Since its inception in 1991, OCT has progressed through multiple iterations, from time-domain OCT, to spectral-domain OCT, to swept-source OCT, all of which have progressively improved the resolution and speed of scans. Even newer technological advancements and OCT applications, such as adaptive optics, visible-light OCT, and OCT-angiography, have enriched the use of OCT in the evaluation of glaucoma. This article reviews current commercial and state-of-the-art OCT technologies and analytic techniques in the context of their utility for glaucoma diagnosis and management, as well as promising future directions. Expected final online publication date for the Annual Review of Vision Science, Volume 7 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Optical Coherence Tomography Evaluation of Peripapillary and Macular Structure Changes in Pre-perimetric Glaucoma, Early Perimetric Glaucoma, and Ocular Hypertension: A Systematic Review and Meta-Analysis

Background: This study aimed to assess the differences in the average and sectoral peripapillary retinal nerve fiber layer (pRNFL), macular ganglion cell plus inner plexiform layer (mGCIPL), and macular ganglion cell complex (mGCC) thickness using optical coherence tomography (OCT) in patients with pre-perimetric glaucoma (PPG) compared to those with early perimetric glaucoma (EG) and ocular hypertension (OHT).

Methods: A comprehensive literature search of the PubMed database, the Cochrane Library, and Embase was performed from inception to March 2021. The weighted mean difference (WMD) with the 95% confidence interval (CI) was pooled for continuous outcomes.

Results: Twenty-three cross-sectional studies comprising 2,574 eyes (1,101 PPG eyes, 1,233 EG eyes, and 240 OHT eyes) were included in the systematic review and meta-analysis. The pooled results demonstrated that the average pRNFL (WMD = 8.22, 95% CI = 6.32–10.12, P < 0.00001), mGCIPL (WMD = 4.83, 95% CI = 3.43–6.23, P < 0.00001), and mGCC (WMD = 7.19, 95% CI = 4.52–9.85, P < 0.00001) were significantly thinner in patients with EG than in those with PPG. The sectoral thickness of pRNFL, mGCIPL, and mGCC were also significantly lower in the EG eyes. In addition, the average pRNFL and mGCC were significantly thinner in the PPG eyes than those in the OHT eyes (pRNFL: WMD = −8.57, 95% CI = −9.88 to −7.27, P < 0.00001; mGCC: WMD = −3.23, 95% CI = −6.03 to −0.44, P = 0.02). Similarly, the sectoral pRNFL and mGCC were also significantly thinner in the PPG eyes than those in the OHT eyes.

Conclusion: OCT-based measurements of peripapillary and macular structural alterations can be used to distinguish PPG from EG and OHT, which can help understand the pathophysiology of glaucoma at earlier stages. Studies that employ clock hour classification methods and longitudinal studies are needed to verify our findings.

Systematic Review Registration:https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=239798 CRD42021239798

Effect of algorithms and covariates in glaucoma diagnosis with optical coherence tomography angiography

PURPOSE

To assess the effects of algorithms and covariates in glaucoma diagnosis with optical coherence tomography angiography (OCTA).

METHODS

In this prospective cross-sectional study, one eye each of 36 normal controls and 64 patients with glaucoma underwent 4.5 mm disc-centred and 6 mm macula-centred OCTA scans. The peripapillary nerve fibre layer plexus capillary density (NFLP-CD) and macular superficial vascular complex vessel density (SVC-VD) were measured using both a commercial algorithm (AngioAnalytics) and a custom algorithm (Center for Ophthalmic Optics & Lasers Angiography Reading Toolkit (COOL-ART)). The nerve fibre layer and ganglion cell complex thicknesses were measured on structural OCT.

RESULTS

The overall peripapillary NFLP-CD and macular SVC-VD measured with the two algorithms were highly correlated but poorly agreed. Among the normal controls, the perfusion measurements made by both algorithms were significantly correlated with age. AngioAnalytics measurements were also correlated with signal strength index, while COOL-ART measurements were not. These covariates were adjusted. The diagnostic accuracy, measured as the area under the receiver operating characteristic curve for glaucoma detection, was not significantly different between algorithms, between structural and perfusion parameters and between the peripapillary and macular regions (All p>0.05). The macular SVC-VD in the 6 mm square had a significantly higher diagnostic accuracy than that of the central 3 mm square area (p=0.005).

CONCLUSIONS

AngioAnalytics and COOL-ART vessel density measurements are not interchangeable but potentially interconvertible. Age and signal strength are significant covariates that need to be considered. Both algorithms and both peripapillary and macular perfusion parameters have similarly good diagnostic accuracy comparable to structural OCT. A larger macular analytic area provides higher diagnostic accuracy.

Glaucoma diagnostic capabilities of macular vessel density on optical coherence tomography angiography: superficial versus deep layers

BACKGROUND/AIMS

To compare glaucoma diagnostic capabilities of superficial and deep macular vessel density (mVD) parameters in a series of healthy and open-angle glaucoma (OAG) eyes with central visual field (CVF) loss.

METHODS

We consecutively enrolled 113 eyes of 113 patients with OAG and 47 eyes of 47 healthy participants in a retrospective manner. Superficial and deep mVDs were measured at foveal, parafoveal and perifoveal locations on optical coherence tomography (OCT) angiography. The macular ganglion cell-inner plexiform layer thickness (mGCIPLT) was measured on OCT as a reference standard. Glaucoma diagnostic capabilities of superficial and deep mVD parameters were assessed according to the glaucoma stage. Factors associated with the CVF mean sensitivity (MS) were evaluated using linear regression analyses in the OAG eyes.

RESULTS

Glaucoma diagnostic capabilities of superficial perifoveal and parafoveal mVDs were significantly better than those of deep perifoveal and parafoveal mVDs, regardless of the glaucoma stage (both p<0.05). Both mGCIPLT and superficial parafoveal mVD were significantly associated with CVF MS (β-coefficients=10.567 and 21.147, respectively, both p<0.05), independent of age and glaucoma severity.

CONCLUSION

Superficial mVD parameters showed significantly greater glaucoma diagnostic capabilities and better correlation with CVF MS compared with deep mVD parameters.

OCT Angiography for the Diagnosis of Glaucoma: A Report by the American Academy of Ophthalmology

PURPOSE

To review the current published literature on the use of OCT angiography (OCTA) to help detect changes associated with the diagnosis of primary open-angle glaucoma.

METHODS

Searches of the peer-reviewed literature were conducted in March 2018, June 2018, April 2019, December 2019, and June 2020 in the PubMed and Cochrane Library databases. Abstracts of 459 articles were examined to exclude reviews and non-English articles. After inclusion and exclusion criteria were applied, 75 articles were selected and the panel methodologist rated them for strength of evidence. Three articles were rated level I and 57 articles were rated level II. The 15 level III articles were excluded.

RESULTS

OCT angiography can detect decreased capillary vessel density within the peripapillary nerve fiber layer (level II) and macula (level I and II) in patients with suspected glaucoma, preperimetric glaucoma, and perimetric glaucoma. The degree of vessel density loss correlates significantly with glaucoma severity both overall and topographically (level II) as well as longitudinally (level I). For differentiating glaucomatous from healthy eyes, some studies found that peripapillary and macular vessel density measurements by OCTA show a diagnostic ability (area under the receiver operating characteristic curve) that is comparable with structural OCT retinal nerve fiber and ganglion cell thickness measurements, whereas other studies found that structural OCT measurements perform better. Choroidal or deep-layer microvasculature dropout as measured by OCTA is also associated with glaucoma damage (level I and II). Lower peripapillary and macular vessel density and choroidal microvasculature dropout are associated with faster rates of disease progression (level I and II).

CONCLUSIONS

Vessel density loss associated with glaucoma can be detected by OCTA. Peripapillary, macular, and choroidal vessel density parameters may complement visual field and structural OCT measurements in the diagnosis of glaucoma.

Choriocapillaris thickness and density in axially elongated eyes

PURPOSE

Axial myopia is characterized by a thinning of the choroid. We examined whether the myopic choroidal thinning also includes a thinning of the choriocapillaris.

METHODS

Using light microscopy, we measured thickness and density of the choriocapillaris at the posterior pole, posterior pole-equator midpoint (PPEMP), equator and close to the ora serrata on histological sections of 58 enucleated human globes (mean age: 62.4 ± 17.8 years; range: 24-88 years; mean axial length: 27.8 ± 4.0 mm; range: 22.0-37.0 mm).

RESULTS

Choriocapillaris thickness decreased (p < 0.001) from the posterior pole (median: 3.9 µm; interquartile range (IQR): 3.3-6.0) to the equator (median: 2.7 µm; IQR: 1.5, 4.2). It was not significantly associated with axial length, neither at the posterior pole (p = 0.25), the PPEMP (p = 0.81), equator (p = 0.80) or ora serrata (p = 0.50). Mean choriocapillaris density decreased from the posterior pole to the equator (198 µm/300 µm; IQR: 152/300, 246/300 versus 156 µm/300 µm; IQR: 72/300, 216/300; p < 0.001). Choriocapillaris density was not significantly associated with axial length (posterior pole: p = 0.07; PPEMP: p = 0.33; equator: p = 0.22; ora serrata: p = 0.36).

CONCLUSIONS

The choriocapillaris thickness and density, decreasing from the posterior pole to the fundus periphery, were not significantly associated with axial length. These findings may be of interest for the understanding of high myopia and pathologic myopia.

Discrepancy in Loss of Macular Perfusion Density and Ganglion Cell Layer Thickness in Early Glaucoma

PURPOSE

To identify characteristics of patients with early open-angle glaucoma exhibiting greater macular perfusion density (PD) loss compared with macular ganglion cell layer (GCL) thickness loss.

DESIGN

Cross-sectional study.

METHODS

Optical coherence tomography (OCT) imaging of the optic nerve head and macula was conducted in patients and healthy control subjects. Minimum rim width, retinal nerve fiber layer and GCL thickness, and PD from OCT angiography were derived. Only high-quality images were included. For direct comparison, raw PD and GCL thickness values in patients were converted to relative age-corrected loss values based on data from controls. Demographic and ocular variables related to greater PD loss compared with GCL thickness loss were identified with multivariate logistic regression.

RESULTS

Data from 89 patients (median mean deviation with the 24-2 and 10-2 tests, Humphrey Field Analyzer: -1.96 dB and -1.49 dB, respectively) and 54 controls were analyzed. Sixty-three (71%) patients had relatively more GCL thickness loss, whereas 26 (29%) had relatively more PD loss. More PD loss was associated with lower OCT and OCT-angiography signal strength (odds ratio [95% confidence interval], 0.64 [0.40, 0.96] and 0.60 [0.38, 0.86], per dB, respectively), thicker retinal nerve fiber layer thickness (1.08 [1.01, 1.16] per μm), and female sex (6.57 [1.25, 48.79]).

CONCLUSION

Less than one-third of patients with early glaucoma had more loss of perfusion compared with conventional structural loss in the macula. Even within a range of high-quality images, lower signal strength may be at least partially responsible for apparent perfusion loss.

OCT angiography analysis of retinal vessel density in primary open-angle glaucoma with and without Tafluprost therapy

Background

Primary open-angle glaucoma (POAG) is a progressive neurodegenerative disease which leads to irreversible blindness. An elevated intraocular pressure (IOP) is considered to be the main risk factor for the disease progression. It is known that retinal blood flow is altered in POAG eyes. Tafluprost, a prostaglandin analogue which lowers the IOP, has shown to also improve the retinal blood flow in animals.

Methods

The current study therefore evaluated the retinal vessel density in the peripapillary and macular region of POAG patients with normal IOP treated with topical Tafluprost (n = 20) compared to surgically treated patients with normal IOP (n = 22) using optical coherence tomography angiography (OCT-A). The retinal flow density was obtained after binarisation and evaluated in five sectors.

Results

There was a significantly higher peripapillary flow density in all sectors in Tafluprost treated eyes when compared to post-surgery eyes. The flow density in the inferior sector of the superficial plexus in the macular region was also significantly higher in the Tafluprost group.

Conclusions: These results indicate that Tafluprost not only lowers IOP, but may also enhance retinal blood flow in POAG patients with a normal IOP.

Global assessment of arteriolar, venular and capillary changes in normal tension glaucoma

Microcirculatory insufficiency has been hypothesized in glaucoma pathogenesis. There is a scarcity of data to comprehensively examine the changes in retinal microvasculature and its role in normal tension glaucoma (NTG). We conducted a cross-sectional case-control study and included 168 eyes from 100 NTG patients and 68 healthy subjects. Quantitative retinal arteriolar and venular metrics were measured from retinal photographs using a computer-assisted program. Radial peripapillary capillary network was imaged with OCT-A and quantitative capillary metrics (circumpapillary vessel density (cpVD) and circumpapillary fractal dimension (cpFD)) were measured with a customized MATLAB program. We found that NTG was associated with decreased arteriolar and venular tortuosity, arteriolar branching angle, cpVD and cpFD. Decreased venular caliber, arteriolar and venular branching angles, cpVD and cpFD were associated with thinner average RNFL thickness. Decreased arteriolar and venular branching angles, cpVD and cpFD were also associated with worse standard automated perimetry measurements (mean deviation and visual field index). Compared with retinal arteriolar and venular metrics, regression models based on OCT-A capillary metrics consistently showed stronger associations with NTG and structural and functional measurements in NTG. We concluded that NTG eyes showed generalized microvascular attenuations, in which OCT-A capillary metrics attenuations were more prominent and strongly associated with NTG.

Optical Coherence Tomography Angiography in Glaucoma

Optical coherence tomography angiography (OCTA) is a relatively new, noninvasive, dye-free imaging modality that provides a qualitative and quantitative assessment of the vasculature in the retina and optic nerve head. OCTA also enables visualization of the choriocapillaris, but only in areas of parapapillary atrophy. With OCTA, the movement of red blood cells is used as a contrast to delineate blood vessels from static tissues. The features seen with OCTA in eyes with glaucoma are reduction in the superficial vessel density in the peripapillary and macular areas, and complete loss of choriocapillaris in localized regions of parapapillary atrophy (called deep-layer microvascular dropout). These OCTA changes correlate well topographically with the functional changes seen on visual field examination and structural changes seen on optical coherence tomography (OCT) (ie, parapapillary retinal nerve fiber layer changes and inner retinal layer thickness changes at macula). The OCTA measurements also have acceptable test-retest variability and well differentiate glaucomatous from normal eyes. OCTA measurements can be affected by various subject-related, eye-related, and disease-related factors. Vessel density reduction on OCTA reaches a base level (floor) at a more advanced disease stage than the structural changes on OCT and therefore has the potential to monitor progression in eyes with advanced glaucomatous damage. OCTA also adds information about glaucoma patients at risk of faster progression. OCTA, therefore, complements visual field and OCT examinations to diagnose glaucoma, detect progression, and assess risk of progression.

Asymmetry analysis of optical coherence tomography angiography macular perfusion density measurements in preperimetric and perimetric glaucoma

Macular retinal layer thickness asymmetry indices, particularly for the ganglion cell layer, are promising early indicators of glaucomatous damage. We evaluated macular perfusion density asymmetry (MPDA) among normal, preperimetric glaucoma (PPG), and perimetric glaucoma (PG) eyes, and we tested the performance of MPDA in differentiating between control and glaucoma eyes with or without visual field (VF) defects. In this study, 116 eyes (39 normal, 27 PPG, and 50 PG eyes) with optical coherence tomography angiography images of the macula were analysed. No significant difference was found in outer and inner MPDA between the control and PPG groups. However, outer MPDA was significantly higher in the PG group than in the PPG group (p = 0.009). Asymmetry of perfusion density and structural parameters was compared; no significant difference was found between controls and glaucoma patients. Outer MPDA had significantly higher discrimination ability between PPG and PG than did macular ganglion cell layer–inner plexiform layer thickness asymmetry (p = 0.039). In conclusion, the discriminant capability of MPDA for discriminating between glaucoma patients with and without VF defects is significantly higher than that of structural asymmetry. MPDA may be helpful in monitoring glaucoma progression in clinical practice.

Optical coherence tomography angiography in glaucoma

Assessment of the vasculature within the optic nerve, peripapillary superficial retina, macula, and peripapillary choroid can be determined in glaucoma using optical coherence tomography angiography (OCTA). Decreased perfusion within the pre-laminar layer of the optic nerve has been correlated with glaucoma severity. The peripapillary superficial retinal vessel density allows diagnosis and detection of glaucoma progression in a manner similar to the peripapillary retinal nerve fiber layer (RNFL) thickness. Furthermore, decreased peripapillary vessel density of the intact hemiretina or unaffected eye of glaucomatous eyes suggests that vascular changes can occur prior to detectable visual field damage. The accuracy for glaucoma detection of the macular ganglion cell (MGC) thickness compared to macular vessel density has differed among studies. Several studies have reported reduction of macular vessel density as well as its ganglion cell thickness. Results of studies evaluating the parapapillary choroid have shown a greater prevalence of choroidal microvasculature dropout in glaucomatous eyes with a parapapillary gamma zone, which is associated with central visual field defects or glaucoma progression. It remains unclear whether the reduced vessel density in glaucoma is a primary event or secondary to glaucomatous damage. Further studies are warranted to elucidate this question.

Phacoemulsification Induced Changes of Choroidal Thickness in Eyes with Age-Related Macular Degeneration

Background and Objectives: Patients with cataract and age-related macular degeneration (AMD) may safely undergo cataract phacoemulsification to enhance visual acuity. Although it has not been proven that cataract surgery can cause AMD progression, different phacoemulsification effects are observed not only on retinal but also on choroidal tissues. The purpose of this study was to evaluate the effect of phacoemulsification on the choroidal thickness (CT) in eyes with and without AMD. Materials and Methods: In 32 eyes of 32 patients with senile cataract (No-AMD group) and in 32 eyes of 32 patients with cataract and dry AMD (AMD group), who had phacoemulsification without intraoperative complications and intraocular lens implantation, foveal retinal thickness (FRT) and CT were evaluated three times: at 1–2 post meridiem preoperatively, then 1 month and 3 months postoperatively, using 1050 nm swept source-optical coherence tomography (Topcon, Tokyo, Japan). Results: In both groups, a significant increase in FRT was observed after one month and a decrease after three months without reaching the baseline. One month after surgery, a sectorial CT increase was apparent in all sectors in both groups. A negative association between CT and age was disclosed in the No-AMD group almost for all regions at all time points. Furthermore, CT was significantly negatively associated with axial length (AL) in all sectors at all time points in the AMD group. Conclusion: Uneventful phacoemulsification may induce changes in the posterior eye segment. An increase in CT and FRT was observed in both groups one month after the surgery. However, three months after surgery, CT changes were different in both groups, while FRT decreased in both groups. CT changes negatively associated with age in the No-AMD group and with AL in the AMD eyes. These postoperative changes in the choroid and retina may not only lead to the late-onset pseudophakic cystoid macular edema but also to progression of AMD.

Optical coherence tomography angiography of the peripapillary region and macula in normal, primary open angle glaucoma, pseudoexfoliation glaucoma and ocular hypertension eyes

AIM

To evaluate and compare the peripapillary and retinal vasculature changes in primary open angle glaucoma (POAG), pseudoexfoliation glaucoma (PXG), ocular hypertension (OHT) and normal eyes using optical coherence tomography angiography (OCTA).

METHODS

A total of 114 POAG, PXG and OHT eyes of 60 patients and 46 eyes of 23 healthy control participants with good quality OCTA images were included. The PXG, POAG, OHT, and control groups (aged 68.17±6.30y, 61.11±10.26y, 58.1±8.9y, and 56.9±4.6y, respectively) contained of 46, 36, 32, and 46 eyes, respectively. Measurements of vessel density (VD) in the peripapillary region and macula, average retinal inner thickness, and retinal nerve fiber layer thickness (RNFLT) were compared among groups. In order to test the accuracy of differentiation between eyes with and without glaucoma, the area was calculated under the receiver operating characteristic (ROC) curves.

RESULTS

The VD in glaucomatous eyes was significantly lower than the control group in all peripapillary sectors (44.35%±6.78% vs 50.47%±1.83%, P<0.001), the superficial (44.08%±5.46% vs 51.28%±2.85%, P<0.001) and the deep (45.13%±8.55% vs 54.20%±5.44%, P<0.001) vascular plexus. There was a significant difference in peripapillary VD between glaucomatous and OHT eyes (44.35%±6.78% vs 49.86%±2.45%, P<0.001). The OHT group featured a lower superficial (48.06%±4.32% vs 51.28%±2.85%, P=0.027) and deep plexus (48.70%±5.99% vs 54.20%±5.44%, P=0.013) whole image vessel density (wiVD) than did the control group. The average macular superficial plexus wiVD was significantly lower in eyes with PXG than in eyes with POAG (42.22%±5.36% vs 46.54%±5.56%, P=0.046).

CONCLUSION

OCTA can measure reduced peripapillary and macular VD in eyes with glaucoma and OHT, and these results are correlated to functional and structural glaucomatous alterations. Peripapillary and macular superficial plexus VD is lower in eyes with PXG than in eyes with POAG. Furthermore, the OHT eyes demonstrate impaired macular vasculature in both superficial and deep plexus.

Macular imaging with optical coherence tomography in glaucoma

With the advent of spectral-domain optical coherence tomography, imaging of the posterior segment of the eye can be carried out rapidly at multiple anatomical locations, including the optic nerve head, circumpapillary retinal nerve fiber layer, and macula. There is now ample evidence to support the role of spectral-domain optical coherence tomography imaging of the macula for detection of early glaucoma. Macular spectral-domain optical coherence tomography measurements demonstrate high reproducibility, and evidence on its utility for detection of glaucoma progression is accumulating. We present a comprehensive review of macular spectral-domain optical coherence tomography imaging emerging as an essential diagnostic tool in glaucoma.

Diagnostic ability of vessel density measured by spectral-domain optical coherence tomography angiography for glaucoma in patients with high myopia

Although early glaucoma detection is important to prevent visual loss due to disease progression, its clinical diagnosis in highly myopic eyes is still difficult. Many studies using optical coherence tomography (OCT) angiography (OCTA) reported decreased vessel density (VD) in glaucomatous eyes compared to normal eyes. We evaluated the diagnostic ability of peripapillary VD and macular VD measured by OCTA, comparing them with conventional valuables such as peripapillary retinal nerve fibre layer (RNFL) thickness and macular ganglion cell-inner plexiform layer (GCIPL) thickness measured by OCT. We also calculated the average VD ratio (VDR) (average outer macular VD/average inner macular VD), superior VDR (superior outer macular VD/average inner macular VD), and inferior VDR (inferior outer macular VD/average inner macular VD). Totally, 169 eyes from 169 subjects were enrolled. Among OCTA measurements, the best diagnostic parameters were average VDR (AUROC: 0.852 and 0.909) and inferior VDR (AUROC: 0.820 and 0.941) in nonhighly and highly myopic eyes, respectively. Inferior VDR showed better diagnostic ability than most of the other OCT measurements including peripapillary RNFL thickness and macular GCIPL thickness in highly myopic eyes. Accordingly, OCTA measurements can be useful for diagnosing glaucoma in highly myopic eyes, especially when using calculated indices such as average VDR or inferior VDR.

Differences in swept-source OCT angiography of the macular capillary network in high tension and normal tension glaucoma

AIM OF THE STUDY

The purpose of the present study was to determine if swept-source optical coherence tomography angiography (OCTA) of the superficial plexus in the macular region can detect differences between high-tension open-angle glaucoma (HTG) and normal-tension glaucoma (NTG).

MATERIALS AND METHODS

In this prospective study 60 eyes from 60 patients (40 HTG; 20 NTG) underwent fovea centred 3 × 3 mm cube macula OCTA imaging by a swept-source OCTA device (Plex Elite, Zeiss, Jena, Germany). Quantitative analysis of the vasculature at the superficial plexus was performed by assessing the Perfusion Density (PD), defined as the total area of perfused vasculature per unit area in a region of measurement, for each group, respectively. Besides, macular ganglion cell layer thickness and mean deviation from visual field testing was assessed and correlated with PD.

RESULTS

Average superficial PD of the measured 3 × 3 mm field was comparable between HTG and NTG (P = .567). In both groups a significant relation of PD and age (HTG: r = -0.48, p = .002; NTG: r = -0.615; p = .004) was shown, indicating reduced PD with increasing age. For both groups a positive correlation between PD and mean deviation (MD) (HTG: r = 0.492, p = .003; NTG: r = 0.530, p = .029) as well as PD and GCL thickness was shown (r = 0.486, p = .002 vs. r = 0.389; p = .09). However, the latter did not reach statistical significance in the NTG group.

CONCLUSION

PD at the central 3 mm around the fovea is comparable between HTG and NTG. Significant correlation with age and MD was shown in both groups.

Macular vessel density versus ganglion cell complex thickness for detection of early primary open-angle glaucoma

Background

To evaluate the macular vessel density (VD) and ganglion cell complex (GCC) thickness in pre-perimetric (PPG) and early perimetric primary open-angle glaucoma (PG) eyes, and to compare the diagnostic ability of the two measurements to discriminate PPG and early PG eyes from healthy eyes.

Methods

Seventy-nine eyes in 72 subjects (31 normal, 26 PPG, and 22 early PG eyes) were included in the consecutive case series. Macular VD and GCC thickness were acquired simultaneously using the 6 × 6 mm² high-density AngioRetina scanning mode. Diagnostic abilities were assessed using the area under the receiver operating characteristic curve (AUROC).

Results

Compared to healthy eyes, whole image VD (wiVD) and GCC thickness were significantly lower in PPG and early PG eyes (all P < 0.025). The percent reduction of wiVD was lower than that of GCC thickness in early PG eyes (P < 0.05), while they were similar in PPG eyes (P > 0.05). Regionally, greater VD attenuation and GCC thinning were identified in the perifovea than in the parafovea in both groups (all P < 0.05). Moreover, the percent reduction of VD was less than that of GCC thickness in the perifoveal region in PPG eyes (P < 0.05). The AUROCs for wiVD and GCC thickness were 0.824 and 0.881, respectively, in PPG eyes (P > 0.05), and 0.918 and 0.977, respectively, in early PG eyes (P > 0.05).

Conclusions

Macular VD and GCC thickness significantly decreased in PPG and early PG eyes. The perifoveal region appeared to be more vulnerable to macular VD attenuation and GCC thinning in early glaucoma. Our results showed that macular VD measurements may be helpful for detecting and understanding early glaucomatous damage.

Optical coherence tomography and optical coherence tomography angiography in glaucoma: diagnosis, progression, and correlation with functional tests

The present review will summarize the most updated findings with regards to optical coherence tomography and optical coherence tomography angiography in glaucoma, highlighting their clinical use for detection and monitoring of the disease, and their correlation to functional tests (such as visual field) widely employed in the asset of modern glaucoma clinics.

Macular vessel density in untreated normal tension glaucoma with a hemifield defect

PURPOSE

To investigate macular vessel density (MVD) and structural alterations in untreated normal tension glaucoma (NTG) with a hemifield defect (HFD) and to compare these with the findings in healthy eyes.

STUDY DESIGN

Case series with a healthy group for comparison.

METHODS

Thirty-four eyes of 34 untreated NTG patients with HFD and 28 eyes of 28 healthy subjects were enrolled. RTVue-XR Avanti^TM (Optovue, Inc.), a combined OCT-A and SD-OCT system, was used to determine MVD and inner macular thickness (IMT) measurements. Mean circumpapillary retinal nerve fiber (cpRNFL) and macular ganglion cell complex (mGCC) thicknesses were measured with the RTVue-100^TM (Optovue, Inc.). Wilcoxon signed-rank test was used to evaluate differences between defective and normal hemifields in NTG eyes and Mann-Whitney U test to evaluate differences between normal hemifields in NTG eyes and healthy eyes.

RESULTS

In comparison with healthy eyes, the normal hemifields of NTG eyes showed significantly reduced MVD, as well as cpRNFL and mGCC thicknesses, although IMT did not differ between the two groups. The defective hemifield in NTG eyes showed significantly reduced IMT, as well as cpRNFL and mGCC thicknesses, compared with the normal hemifield, although MVD did not differ between the two hemifields.

CONCLUSION

Hemodynamic deficiencies and structural damage might have already begun in the perimetrically normal hemifields of NTG eyes. Further studies are needed to elucidate whether the reduction in MVD may precede structural changes or the reduction in vasculature and structural loss may vary with disease severity in at least in some cases.

Comparison of a commercial spectral-domain OCT and swept-source OCT based on an angiography scan for measuring circumpapillary retinal nerve fibre layer thickness

Background/aims

To assess the agreement in measuring retinal nerve fibre layer (RNFL) thickness between spectral-domain (SD; Cirrus HD, Carl Zeiss Meditec, USA) optical coherence tomography (OCT) and swept-source (SS; Plex Elite 9000, Carl Zeiss Meditec) OCT using an OCT angiography (OCTA) scanning protocol.

Methods

57 participants (12 glaucomatous, 8 ocular hypertensive and 74 normal eyes) were scanned with two OCT instruments by a single experienced operator on the same day. Circumpapillary RNFL thicknesses were automatically segmented for SD-OCT and manually segmented for SS-OCTA scans. Agreement of global RNFL thickness, as well as average thickness in four quadrants was assessed using intraclass correlation coefficients (ICCs).

Results

There was excellent agreement in the inferior and superior quadrants and the global (all ICC >0.90), followed by good agreement in the temporal (ICC=0.79) and nasal (ICC=0.73) quadrants. The ICC values were similar in the subgroups except within the ocular hypertension group, where the nasal quadrant was less agreeable (ICC=0.31). SS-OCTA-derived RNFL thickness was on average 3 µm thicker than SD-OCT, particularly in the nasal (69.7±11.5 µm vs 66.3±9.3 µm; p<0.001) and temporal (75.6±13.7 µm vs 67.9±12.3 µm; p<0.001) quadrants.

Conclusions

RNFL measurements taken with SS-OCTA have good-to-excellent agreement with SD-OCT, which suggests that the RNFL thickness can be sufficiently extracted from wide-field OCTA scans.

Optical Coherence Tomography Angiography in Mice: Quantitative Analysis After Experimental Models of Retinal Damage

Purpose

We implemented optical coherence tomography angiography (OCT-A) in mice to: (1) develop quantitative parameters from OCT-A images, (2) measure the reproducibility of the parameters, and (3) determine the impact of experimental models of inner and outer retinal damage on OCT-A findings.

Methods

OCT-A images were acquired with a customized system (Spectralis Multiline OCT2). To assess reproducibility, imaging was performed five times over 1 month. Inner retinal damage was induced with optic nerve transection, crush, or intravitreal N-methyl-d-aspartic acid injection in transgenic mice with fluorescently labeled retinal ganglion cells (RGCs). Light-induced retinal damage was induced in albino mice. Mice were imaged at baseline and serially post injury. Perfusion density, vessel length, and branch points were computed from OCT-A images of the superficial, intermediate, and deep vascular plexuses.

Results

The range of relative differences measured between sessions across the vascular plexuses were: perfusion density (2.8%-7.0%), vessel length (1.9%-4.1%), and branch points (1.9%-5.0%). In mice with progressive RGC loss, imaged serially and culminating in around 70% loss in the fluorescence signal and 18% loss in inner retinal thickness, there were no measurable changes in any OCT-A parameter up to 4 months post injury that exceeded measurement variability. However, light-induced retinal damage elicited a progressive loss of the deep vascular plexus signal, starting as early as 3 days post injury.

Conclusions

Vessel length and branch points were generally the most reproducible among the parameters. Injury causing RGC loss in mice did not elicit an early change in the OCT-A signal.

Circumpapillary and macular vessel density assessment by optical coherence tomography angiography in eyes with temporal hemianopia from chiasmal compression. Correlation with retinal neural and visual field loss

AIMS

To compare the circumpapillary and macular vessel density (cpVD/mVD) of eyes with temporal visual field (VF) defect and band atrophy (BA) of the optic nerve and normal controls using OCTA and to verify the association of VD parameters with circumpapillary retinal nerve fibre layer (cpRNFL) thickness, macular ganglion cell complex (mGCC) thickness and VF loss.

METHODS

Thirty-three eyes of 26 patients with BA and 42 eyes of 22 age-matched normal controls underwent OCT + OCTA scanning. cpVD and cpRNFL were expressed as average and sector measurements. mVD and mGCC were calculated as averages and in quadrants and hemiretinas. VF loss was estimated using the 24-2 and the 10-2 protocols. Generalized estimated equation models were used for comparisons and area under the receiver operating characteristics (AROC) were calculated.

RESULTS

Compared with controls, BA eyes displayed smaller average cpVD and mVD values (p < 0.001 and AROC = 0.91 for both). Sectorial measurements were also reduced, especially the nasotemporal sector average cpVD (p < 0.001 and AROC = 0.96) and the nasal retina mVD measurements (p < 0.001 and AROC = 0.93). cpVD and mVD correlated strongly with corresponding cpRNFL and mGCC thickness measurements in affected regions (r range: 0.67-0.78 and 0.56-0.76, respectively). Similarly, cpVD and mVD parameters correlated significantly with corresponding VF loss (r range: 0.45-0.68).

CONCLUSIONS

cpVD and mVD are significantly reduced in BA eyes compared with controls and are strongly correlated with retinal neural and VF loss. cpVD and mVD reduction on OCTA could serve as a surrogate for retinal neural loss in compressive optic neuropathy and might be useful in its management.

A Review of OCT Angiography in Glaucoma

There is growing evidence that vascular dysfunction plays a role in the pathogenesis of glaucoma. The details of this relationship have remained elusive partially due to limitations in our ability to assess blood flow in the optic nerve. Optical coherence tomography angiography (OCTA) has emerged as a promising new technology well positioned to become the first clinically suitable test of optic nerve perfusion. OCTA uses the motion of red blood cells as an intrinsic contrast agent to create reproducible images of microvascular networks rapidly and non-invasively. A significant body of research regarding the use of OCTA in glaucoma has emerged in recent years. This review aims to provide an overview of the basic principles underlying OCTA technology, summarize the current literature regarding the application of OCTA in the management of glaucoma, and address the role of OCTA in explicating the vascular pathogenesis of glaucoma.

Macula Vessel Density and Thickness in Early Primary Open-Angle Glaucoma

PURPOSE

To characterize and compare the ganglion cell complex (GCC) thickness and macula vessel density in preperimetric and early primary open-angle glaucoma (POAG) eyes.

DESIGN

Cross-sectional study.

METHODS

Fifty-seven healthy, 68 preperimetric, and 162 early POAG eyes enrolled in the Diagnostic Innovations in Glaucoma Study. Optical coherence tomography angiography (OCT-A)-based superficial macula vessel density and OCT-based GCC thickness were evaluated simultaneously. Percent loss from normal of GCC thickness and macula vessel density was compared. Area under the receiver operating characteristic curve was used to describe the diagnostic utility.

RESULTS

Both GCC thickness and vessel density were significantly lower in preperimetric and early POAG eyes compared to healthy eyes. Compared to the preperimetric POAG group, the early POAG group showed larger GCC thickness percent loss (whole image 4.72% vs 9.86%; all P < .01) but similar vessel density percent loss (whole image 4.97% vs 6.93%; all P > .05). In preperimetric POAG, GCC thickness and vessel density percent losses were similar (all P > .1). In contrast, in early POAG, GCC thickness percent loss was larger than that of vessel density (all P ≤ .001). To discriminate preperimetric or early glaucoma eyes from healthy eyes, GCC thickness and macula vessel density showed similar diagnostic accuracy (all P > .05).

CONCLUSIONS

Both GCC thinning and macula vessel density dropout were detectable in preperimetric and early POAG eyes. GCC loss was greater than macula vessel density loss in early perimetric POAG. However, OCT-A and OCT measurements showed similar efficiency to detect early glaucoma.

Optical coherence tomography angiography in glaucoma

PURPOSE OF REVIEW

Optical coherence tomography angiography (OCTA) studies have demonstrated reduced microcirculation in the superficial optic nerve, peripapillary retina, and the macula of glaucoma patients. The scope of this review is to outline recent studies using OCTA in glaucoma and highlight how OCTA may help improve diagnosis and follow-up in glaucoma patients.

RECENT FINDINGS

OCTA studies have provided evidence of vascular changes in the optic nerve head, peripapillary, and macula region in glaucoma in comparison to glaucoma suspects and normal eyes. Additionally, OCTA can detect longitudinal reduction of peripapillary and macula vessel density in glaucoma patients. It remains unclear whether the reduced microcirculation in glaucoma patients induces the neuronal damage or arises through reduced circulation requirements in damaged tissue.

SUMMARY

OCTA is a novel imaging modality that has great potential to enhance our understanding of glaucoma and to improve our ability to detect and treat it.

Optical Coherence Tomography Angiography in Glaucoma

Optical coherence tomography angiography (OCTA) comprises different OCT-based technologies developed for non-invasive assessment and measurement of optic nerve head and retinal perfusion. Currently the most clinically established approach is based on the split spectrum amplitude decorrelation algorithm, which detects moving red blood cells and eliminates all other information. The two main clinical fields in which OCTA offers clinically useful information are investigation of the macular retina (e.g. in macular degeneration and diabetic macular disease) and glaucoma. For glaucoma, the optic nerve head and the peripapillary retinal perfusion in the retinal nerve fiber layer, and the superficial perifoveal macular vasculature are the areas of interest. This review provides a comprehensive summary of the most important current and potential future applications of OCTA in glaucoma, but it does not address the nonglaucomatous optic nerve head or peripapillary and macular diseases.