Measurements of OCT Angiography Complement OCT for Diagnosing Early Primary Open-Angle Glaucoma

Rate of Initial Optic Nerve Head Capillary Density Loss and Risk of Visual Field Progression

Importance

Rapid initial optic nerve head capillary density loss may be used to assess the risk of glaucoma visual field progression.

Objective

To investigate the association between the rate of initial optic nerve head capillary density loss from optical coherence tomography angiography (OCTA) and visual field progression.

Design, Setting, Participants

This was a retrospective study of a longitudinal cohort at a glaucoma referral center. A total of 167 eyes (96 with primary open-angle glaucoma and 71 with glaucoma suspect) of 109 patients were monitored for a mean (SD) of 5.7 (1.4) years from January 2015 to December 2022. Data analysis was undertaken in April 2023.

Main Outcomes and Measures

The rates of initial capillary density and average retinal nerve fiber layer loss were calculated from the first 3 optic nerve head OCTA and OCT scans, respectively, during the initial follow-up (mean [SD], 2.0 [1.0] years). Based on the median rate, eyes were categorized into fast and slow progressor groups. The association between initial capillary density change or retinal nerve fiber layer thinning and visual field progression was evaluated using linear-mixed and time-varying Cox models.

Results

A total of 167 eyes of 109 patients (mean [SD] age, 69.0 [11.1] years; 56 [51.4%] female and 53 [48.6%] male) were assessed. Eighty-three eyes were slow OCTA progressors, while 84 eyes were fast with mean capillary density loss of -0.45% per year and -1.17% per year, respectively (mean difference, -0.72%/year; 95% CI,-0.84 to -0.60; P < .001). Similarly, 83 eyes were slow OCT progressors, while 84 eyes were fast with mean retinal nerve fiber layer thinning of -0.09 μm per year and -0.60 μm per year, respectively (mean difference, -0.51 μm/year; 95% CI,-0.59 to -0.43; P < .001). The fast OCTA and OCT progressors were associated with more rapid visual field loss (mean difference, -0.18 dB/year; 95% CI,-0.30 to -0.06; P = .004 and -0.17 dB/year; 95% CI,-0.29 to -0.06; P = .002, respectively). Fast OCTA progressing eyes were more likely to have visual field progression (hazard ratio, 1.96; 95% CI, 1.04-3.69; P = .04). Seventeen of 52 eyes (32.7%; 95% CI, 32.5-32.8) with fast OCTA and OCT progression developed subsequent visual field likely progression.

Conclusion and Relevance

Rapid initial optic nerve head capillary density loss from OCTA was associated with a faster rate of visual field progression and a doubling of the risk of developing event progression in this study. These findings may support clinical use of OCTA and OCT optic nerve head measurements for risk assessment of glaucoma progression.

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.

Detection and agreement of event-based OCT and OCTA analysis for glaucoma progression

OBJECTIVE

To examine event-based glaucoma progression using optical coherence tomography (OCT) and OCT angiography (OCTA).

METHODS

In this retrospective study, glaucoma eyes with ≥2-year and 4-visits of OCT/OCTA imaging were included. Peripapillary capillary density (CD) and retinal nerve fibre layer thickness (RNFL) were obtained from 4.5 mm × 4.5 mm optic nerve head (ONH) scans. Event-based OCT/OCTA progression was defined as decreases in ONH measurements exceeding test-retest variability on ≥2 consecutive visits. Visual field (VF) progression was defined as significant VF mean deviation worsening rates on ≥2 consecutive visits. Inter-instrument agreement on progression detection was compared using kappa(κ) statistics.

RESULTS

Among 147 eyes (89 participants), OCTA and OCT identified 33(22%) and 25(17%) progressors, respectively. They showed slight agreement (κ = 0.06), with 7(5%) eyes categorized as progressors by both. When incorporating both instruments, the rate of progressors identified increased to 34%. Similar agreement was observed in diagnosis- and severity-stratified analyses (κ < 0.10). Compared to progressors identified only by OCT, progressors identified only by OCTA tended to have thinner baseline RNFL and worse baseline VF. VF progression was identified in 11(7%) eyes. OCT and VF showed fair agreement (κ = 0.26), with 6(4%) eyes categorized as progressors by both. OCTA and VF showed slight agreement (κ = 0.08), with 4(3%) eyes categorized as progressors by both.

CONCLUSIONS

OCT and OCTA showed limited agreement on event-based progression detection, with OCT showing better agreement with VF. Both OCT and OCTA detected more progressors than VF. OCT and OCTA may provide valuable, yet different and complementary, information about glaucoma progression.

Deep Learning Estimation of 10-2 Visual Field Map Based on Macular Optical Coherence Tomography Angiography Measurements

PURPOSE

To develop deep learning (DL) models estimating the central visual field (VF) from optical coherence tomography angiography (OCTA) vessel density (VD) measurements.

DESIGN

Development and validation of a deep learning model.

METHODS

A total of 1051 10-2 VF OCTA pairs from healthy, glaucoma suspects, and glaucoma eyes were included. DL models were trained on en face macula VD images from OCTA to estimate 10-2 mean deviation (MD), pattern standard deviation (PSD), 68 total deviation (TD) and pattern deviation (PD) values and compared with a linear regression (LR) model with the same input. Accuracy of the models was evaluated by calculating the average mean absolute error (MAE) and the R2 (squared Pearson correlation coefficients) of the estimated and actual VF values.

RESULTS

DL models predicting 10-2 MD achieved R2 of 0.85 (95% confidence interval [CI], 74-0.92) for 10-2 MD and MAEs of 1.76 dB (95% CI, 1.39-2.17 dB) for MD. This was significantly better than mean linear estimates for 10-2 MD. The DL model outperformed the LR model for the estimation of pointwise TD values with an average MAE of 2.48 dB (95% CI, 1.99-3.02) and R2 of 0.69 (95% CI, 0.57-0.76) over all test points. The DL model outperformed the LR model for the estimation of all sectors.

CONCLUSIONS

DL models enable the estimation of VF loss from OCTA images with high accuracy. Applying DL to the OCTA images may enhance clinical decision making. It also may improve individualized patient care and risk stratification of patients who are at risk for central VF damage.

Macular Oxygen Saturation in Glaucoma Using Retinal Oximetry of Visible Light Optical Coherence Tomography

Purpose

Oxygen saturation (sO2) plays a critical role in retinal pathophysiology, especially at the macula, which undergoes significant energy consumption. While macular damage has been suggested to be involved in early-stage glaucoma, there has been no report to date on non-invasive macular sO2 in glaucoma. Therefore, we conducted this study to compare macular sO2 associated with other clinical measurements between normal and glaucoma subjects and evaluate whether there are significant differences.

Method

This is a cross-sectional study. We used visible light optical coherence tomography (VIS-OCT) for retinal oximetry in perifoveal vessels. The subjects from groups of normal, suspect/pre-perimetric glaucoma (GS/PPG) and perimetric glaucoma (PG) were scanned using VIS-OCT in the macular region with a sampling density of 512×256 in an area of 5×5 mm2. 48 eyes (16 normal, 17 GS/PPG and 15 PG) were included for the analysis. For each eye, we measured the sO2 of arterioles (AsO2), venules (VsO2), and calculated the difference between arterioles and venules (A-V sO2=AsO2-VsO2), oxygen extraction (OE=(AsO2-VsO2)/AsO2 ×100%). Additionally, we included Zeiss Cirrus OCT scans and 24-2 visual field test (VFT) for clinical benchmark. One-way ANOVA was used to compare the differences among the three groups. Spearman correlation tests were used for correlation sO2 markers to standard metrics including the thickness of ganglion cell layer and inner plexiform layer (GCL+IPL), circumpapillary retinal nerve fiber layer (cpRNFL) and mean deviation (MD) in VFT.

Result

Significant differences were found among three groups for all VIS-OCT, Zeiss OCT, and VFT variables. Macular AsO2, A-V sO2, OE decreased, and VsO2 increased along with severity. Macular AsO2 and A-V sO2 were statistically correlated with GCL+IPL and cpRNFL in all eyes, as well as only PG eyes. Within PG eyes, the correlation between AsO2 and GCL+IPL is dominant in more damaged lower hemifield.

Conclusion

The GS/PPG and PG subjects had significantly higher macular VsO2, lower A-V sO2 and OE indicating less oxygen consumption. The sO2 measured by retinal oximetry of VIS-OCT can be a potential metric for the early diagnosis of glaucoma.

Influence of Refractive Error on Circumpapillary Structure-Function Versus Vessel Density-Function Relationships in Open Angle Glaucoma

PRCIS

In Japanese open angle glaucoma (OAG) eyes correlation of 30-degree visual field mean deviation (MD) and visual field index (VFI) with circumpapillary vessel density is systematically stronger than that with circumpapillary retinal nerve fiber layer thickness (RNFLT), and is preserved in myopia and high myopia.

PURPOSE

The purpose of this study was to investigate the influence of refractive error on the relationship between circumpapillary retinal nerve fiber layer thickness (cpRNFLT) and circumpapillary vessel density (cpVD), respectively, and global visual field parameters in Japanese open angle glaucoma (OAG) eyes.

MATERIAL AND METHODS

One eye of 81 Japanese OAG patients (spherical equivalent refractive error: +3.0 to -9.0 D) underwent 360-degree cpRNFLT and cpVD measurements with Cirrus HD 5000-AngioPlex optical coherence tomography and 30-2 Humphrey visual field testing for mean deviation (MD) and visual field index (VFI) within 1 month. Correlations were determined for the whole population and each refractive error subgroups, separately: emmetropia/hyperopia (n=24), mild (n=18), moderate (n=20), and high myopia (n=19).

RESULTS

For the total population, significant strong to very strong correlations were found between MD, VFI, and both cpRNFLT and cpVD, respectively, with consistently higher r -values for cpVD (highest r -values: 0.532 for cpRNFLT, P <0.001; 0.722 for cpVD, P <0.001). Of the refractive subgroups, statistically significant correlations between cpRNFLT and the visual field parameters were maintained only in the hyperopia/emmetropia and moderate myopia groups. In contrast, statistically significant, strong to very strong correlations between cpVD and both MD and VFI, always exceeding the corresponding r -values found for cpRNFLT were found in all refractive subgroups, with r -values ranging between 0.548 ( P =0.005) and 0.841 ( P <0.001).

CONCLUSIONS

Our results suggest that in Japanese OAG eyes the relationship of MD and VFI with cpVD is strong. It is systematically stronger than that with cpRNFLT and preserved in each conventional refractive error category including high myopia.

Effect of Corneal Hysteresis on the Rates of Microvasculature Loss in Glaucoma

PURPOSE

To investigate the association between corneal hysteresis (CH) and rates of optic nerve head whole image capillary density (wiCD) loss over time in open-angle glaucoma (OAG).

DESIGN

Observational cohort.

PARTICIPANTS

One hundred seventy-four eyes (122 OAG and 52 glaucoma suspect eyes) from 112 patients over more than 2 years and 4 visits or more.

METHODS

Baseline CH measurements were acquired with the Ocular Response Analyzer. Linear mixed-effect models were designed to investigate the effect of CH, average intraocular pressure (IOP) during follow-up, and baseline visual field (VF) mean deviation (MD) on the rates of wiCD loss and circumpapillary retinal nerve fiber layer (cpRNFL) thinning over time, while adjusting for confounders. Interaction between CH or baseline MD and average IOP during follow-up were included in final models to evaluate the effect of baseline MD or average IOP during follow-up on structural changes for different values of CH.

MAIN OUTCOME MEASURE

Effect of CH, IOP, and baseline MD on the rates of wiCD loss and cpRNFL thinning over time.

RESULTS

The average follow-up time was 3.9 years. In the multivariable model, non-Black race, higher average IOP during follow-up, lower baseline CH, lower baseline VF MD, and higher numbers of IOP-lowering medications were associated with faster rates of wiCD loss over time. For CH values 6 mmHg and 12 mmHg, every 1-mmHg increase in average IOP during follow-up was associated with 0.23% per year faster and 0.07% per year slower rates of wiCD loss over time, respectively. While every 1-mmHg decrease in CH was associated with 1.89% per year faster rate of wiCD loss for MD of -12 dB, it was associated with 0.81% per year faster rate of wiCD loss for MD of -3 dB.

CONCLUSION

Lower CH values were significantly associated with faster rates of wiCD loss over time. In eyes with lower CH, both higher average IOP during follow-up and more severe glaucoma damage at baseline were associated with faster rates of wiCD loss and cpRNFL thinning. These results support CH as a useful parameter for risk assessment of glaucoma progression.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Combining Optical Coherence Tomography and Optical Coherence Tomography Angiography Longitudinal Data for the Detection of Visual Field Progression in Glaucoma

PURPOSE

To use longitudinal optical coherence tomography (OCT) and OCT angiography (OCTA) data to detect glaucomatous visual field (VF) progression with a supervised machine learning approach.

DESIGN

Prospective cohort study.

METHODS

One hundred ten eyes of patients with suspected glaucoma (33.6%) and patients with glaucoma (66.4%) with a minimum of 5 24-2 VF tests and 3 optic nerve head and macula images over an average follow-up duration of 4.1 years were included. VF progression was defined using a composite measure including either a "likely progression event" on Guided Progression Analysis, a statistically significant negative slope of VF mean deviation or VF index, or a positive pointwise linear regression event. Feature-based gradient boosting classifiers were developed using different subsets of baseline and longitudinal OCT and OCTA summary parameters. The area under the receiver operating characteristic curve (AUROC) was used to compare the classification performance of different models.

RESULTS

VF progression was detected in 28 eyes (25.5%). The model with combined baseline and longitudinal OCT and OCTA parameters at the global and hemifield levels had the best classification accuracy to detect VF progression (AUROC = 0.89). Models including combined OCT and OCTA parameters had higher classification accuracy compared with those with individual subsets of OCT or OCTA features alone. Including hemifield measurements significantly improved the models' classification accuracy compared with using global measurements alone. Including longitudinal rates of change of OCT and OCTA parameters (AUROCs = 0.80-0.89) considerably increased the classification accuracy of the models with baseline measurements alone (AUROCs = 0.60-0.63).

CONCLUSIONS

Longitudinal OCTA measurements complement OCT-derived structural metrics for the evaluation of functional VF loss in patients with glaucoma.

Multipressure Dial Goggle Effects on Circumpapillary Structure and Microvasculature in Glaucoma Patients

PURPOSE

To evaluate the effects of pressure changes induced by a multipressure dial (MPD) on circumpapillary retinal nerve fiber layer (RNFL) and capillary density (CD) measurements in patients with glaucoma using OCT angiography (OCTA).

DESIGN

Prospective interventional study.

PARTICIPANTS

Twenty-four patients with primary open-angle glaucoma.

METHODS

One eye of each patient underwent negative pressure application with the MPD. The MPD alters intraocular pressure (IOP) relative to atmospheric pressure by generating a negative pressure vacuum within a goggle chamber that is placed over the eye. Each participant underwent serial high density OCTA imaging (AngioVue) of the optic nerve head at different negative pressure increments of -5 mmHg, starting from 0 mmHg, ending at -20 mmHg, and then returning to baseline. Images were acquired after 2 minutes of sustained negative pressure at each target pressure to allow for stabilization of the retinal structures and microvasculature. The RNFL thickness and CD measurements were automatically calculated using the native AngioVue software, and then exported for analysis.

MAIN OUTCOME MEASURES

The influence of different levels of negative pressure on circumpapillary RNFL thickness and CD measurements, assessed by a linear mixed-effects model with repeated measures.

RESULTS

The mean (± SD) age was 71.0 years (± 7.8 years), the baseline IOP was 17.5 mmHg (± 3.6 mmHg), and there was a mean 24-2 mean deviation of -2.80 dB (± 2.55 dB). Serial circumpapillary CD measurements showed a statistically significant dose-dependent increase from baseline, without negative pressure application, to the maximum negative pressure application of -20 mmHg (difference, 2.27%; P = 0.010). Capillary density measurements then decreased symmetrically when lowering the negative pressure to baseline. Circumpapillary CD measurements at target negative pressures of -10 mmHg, -15 mmHg, and -20 mmHg were significantly higher than the baseline measurements (all P values < 0.05). Circumpapillary RNFL thickness remained the same throughout different levels of negative pressure.

CONCLUSIONS

Circumpapillary CD measurements showed a dose-dependent increase with the induction of negative pressure, while RNFL thickness measurements remained unchanged.

Multilayer Macula Vessel Density and Visual Field Progression in Glaucoma

PURPOSE

To evaluate the association of macular superficial vessel density (SVD) and projection-resolved deep vessel density (DVD) with past visual field (VF) progression in patients with primary open-angle glaucoma.

DESIGN

Retrospective cohort.

METHODS

In this longitudinal study, 208 eyes of 147 patients with glaucoma from the Diagnostics Innovations in Glaucoma Study were included. Eligible participants were required to have at least five 24-2 VF tests over a minimum follow-up period of 3 years before macular optical coherence tomography angiography imaging. VF progression was defined based on both event-based pointwise linear regression and trend-based methods. The association of macular SVD and DVD with the probability and rate of past VF progression was evaluated using a linear mixed effects model.

RESULTS

Fifty-two (25%) eyes had VF progression based on the pointwise linear regression based criterion at the end of a mean ± standard deviation follow-up duration of 6.9 ± 1.2 years. In the event-based multivariable analysis, a lower baseline SVD was associated with a higher likelihood of past VF progression (odds ratio per 1% lower. 1.28; 95% confidence interval, 1.02-1.59). Similarly, in the trend-based multivariable analysis, lower macular SVD was associated with a faster past rate of mean deviation decline (coefficient = -0.03 dB/year; 95% confidence interval, -0.04 to -0.01). Event-based and trend-based analyses found no significant associations for macular DVD with the likelihood/rate of past VF progression (P > .05).

CONCLUSIONS

Lower macular SVD, and not DVD, was associated with a higher probability of past VF progression. Macular optical coherence tomography angiography imaging shows promise for identifying eyes at risk of VF progression in patients with glaucoma.

Association of Initial Optical Coherence Tomography Angiography Vessel Density Loss With Faster Visual Field Loss in Glaucoma

IMPORTANCE

Rapid vessel density loss during an initial follow-up period may be associated with the rates of visual field loss over time.

OBJECTIVES

To evaluate the association between the rate of vessel density loss during initial follow-up and the rate of visual field loss during an extended follow-up period in patients suspected of having glaucoma and patients with primary open-angle glaucoma.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study assessed 124 eyes (86 with primary open-angle glaucoma and 38 suspected of having glaucoma) of 82 patients who were followed up at a tertiary glaucoma center for a mean of 4.0 years (95% CI, 3.9-4.1 years) from January 1, 2015, to February 29, 2020. Data analysis for the current study was undertaken in March 2021.

MAIN OUTCOMES AND MEASURES

The rate of vessel density loss was derived from macular whole-image vessel density values from 3 optical coherence tomography angiography scans early during the study. The rate of visual field loss was calculated from visual field mean deviation during the entire follow-up period after the first optical coherence tomography angiography visit. Linear mixed-effects models were used to estimate rates of change.

RESULTS

A total of 124 eyes from 82 patients (mean [SD] age, 69.2 [10.9] years; 41 female [50.0%] and 41 male [50.0%]; and 20 African American [24.4%], 10 Asian [12.2%], 50 White [61.0%], and 2 other race or ethnicity [2.4%]) were assessed. The annual rate of vessel density change was -0.80% (95% CI, -0.88% to -0.72%) during a mean initial follow-up of 2.1 years (95% CI, 1.9-2.3 years). Eyes with annual rates of vessel density loss of -0.75% or greater (n = 62) were categorized as fast progressors, and eyes with annual rates of less than -0.75% (n = 62) were categorized as slow progressors. The annual rate of visual field loss was -0.15 dB (95% CI, -0.29 to -0.01 dB) for the slow optical coherence tomography angiography progressors and -0.43 dB (95% CI, -0.58 to -0.29 dB) for the fast optical coherence tomography angiography progressors (difference, -0.28 dB; 95% CI, -0.48 to -0.08 dB; P = .006). The fast optical coherence tomography angiography progressor group was associated with the faster overall rate of visual field loss in a multivariable model after adjusting to include concurrent visual field mean deviation rate (-0.17 dB; 95% CI, -0.33 to -0.01 dB; P = .04).

CONCLUSIONS AND RELEVANCE

The findings of this cohort study suggest that faster vessel density loss during an initial follow-up period was associated with faster concurrent and subsequent rates of visual field loss during an extended period.

Quantification of localised vascular wedge-shaped defects in glaucoma

BACKGROUND

Vascular dysfunction plays a considerable role in glaucoma pathogenesis. Previous glaucoma case studies described localised wedge-shaped vascular defects, similar to retinal nerve fibre layer (RNFL) wedge defects. This study investigates the prevalence and quantification of this vessel loss, in relation to primary open angle glaucoma (POAG) parameters.

METHODS

This study included 608 eyes (351 participants): 192 PROGRESSA study participants (342 eyes) with suspect, preperimetric or early manifest POAG, observed for vascular wedge defect presence (cohort one); an additional 114 individuals (cohort two-208 eyes) with POAG at various stages of progression for wedge characterisation; and 38 controls (56 eyes). Vascular wedge defects were observed using optical coherence tomography angiography (OCTA). Wedge parameters and vessel densities were quantified using ImageJ software. RNFL and ganglion cell layer inner plexiform layer (GCLIPL) from OCT scans, and mean deviation (Humphrey visual field 24-2) were also assessed.

RESULTS

Vascular wedge defects were found in 45/342 eyes (13.2%) in cohort one, in 41/208 eyes (19.7%) in cohort two and were not found in controls. Wedge defects were mostly inferotemporal (80%), and present at all disease stages. They were associated with visual field loss in the opposite hemisphere, thinner RNFL (p < 0.001), thinner GCLIPL (p = 0.003), and focal RNFL loss corresponding with the vascular defect region.

CONCLUSION

Vascular wedge defects are present at all POAG stages even before functional change and are strongly concordant with focal RNFL loss. Further research is needed to explore these defects in particular their temporal relationship with clinical measures of POAG.