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

Repeatability, interocular correlation and agreement of optic nerve head vessel density in healthy eyes: a swept-source optical coherence tomographic angiography study

AIM

To assess the repeatability, interocular correlation, and agreement of quantitative swept-source optical coherence tomography angiography (OCTA) optic nerve head (ONH) parameters in healthy subjects.

METHODS

Thirty-three healthy subjects were enrolled. The ONH of both eyes were imaged four times by a swept-source-OCTA using a 3 mm ×3 mm scanning protocol. Images of the radial peripapillary capillary were analyzed by a customized Matlab program, and the vessel density, fractal dimension, and vessel diameter index were measured. The repeatability of the four scans was determined by the intraclass correlation coefficient (ICC). The most well-centered optic disc from the four repeated scans was then selected for the interocular correlation and agreement analysis using the Pearson correlation coefficient, ICC and Bland-Altman plots.

RESULTS

All swept-source-OCTA ONH parameters exhibited certain repeatability, with ICC>0.760 and coefficient of variation (CoV)≤7.301%. The obvious interocular correlation was observed for papillary vessel density (ICC=0.857), vessel diameter index (ICC=0.857) and fractal dimension (ICC=0.906), while circumpapillary vessel density exhibited moderate interocular correlation (ICC=0.687). Bland-Altman plots revealed an agreement range of -5.26% to 6.21% for circumpapillary vessel density.

CONCLUSION

OCTA ONH parameters demonstrate good repeatability in healthy subjects. The interocular correlations of papillary vessel density, fractal dimension and vessel diameter index are high, but the correlation for circumpapillary vessel density is moderate.

Longitudinal change of peripapillary vessel density and retinal nerve fibre layer thickness in normal tension and primary angle closure glaucoma

PURPOSE

To compare the rates of peripapillary vessel density (pVD) loss and retinal nerve fibre layer (RNFL) thinning in normal tension glaucoma (NTG) and primary angle closure glaucoma (PACG).

METHODS

Baseline age and severity-matched NTG and PACG eyes (75 eyes of 60 patients for each subtype) were observed longitudinally. All participants' RNFL thickness were measured by optical coherence tomography (OCT); pVD were measured by swept-source OCT-angiography (OCT-A) and quantified by a customised MATLAB program. The rate of pVD loss and RNFL thinning were estimated by linear mixed-effects models.

RESULTS

NTG eyes had significant pVD loss in all sectors (p≤0.05) while PACG eyes' pVD loss was borderline significant in the global region (p=0.05). Significant RNFL thinning was detected in the inferotemporal and superonasal regions of both groups, and the superotemporal region in the NTG group (all p≤0.02). NTG had faster rate of pVD loss in the global (difference (95% CI) -1.08 (-1.90 to -0.27) %/year), temporal (-1.57 (-2.91 to -0.23) %/year) and superotemporal (-1.46 (-2.65 to -0.26) %/year) regions than PACG (all p≤0.02), without significant difference of the rate of RNFL thinning. A lower baseline mean deviation (MD) was associated with a faster rate of global pVD loss, while a lower baseline pVD was associated with a slower rate of global pVD loss in multivariable analyses (both p≤0.04).

CONCLUSIONS

NTG had more extensive and faster rate of pVD loss than PACG. Baseline global pVD and MD were independently associated with the rate of pVD loss in NTG.

Is Primary Open-Angle Glaucoma a Vascular Disease? Assessment of the Relationship between Retinal Arteriolar Morphology and Glaucoma Severity Using Adaptive Optics

BACKGROUND

Retinal vascular abnormalities may be associated with glaucomatous damage. Adaptive optics (AO) is a new technology that enables the analysis of retinal vasculature at the cellular level in vivo. The purpose of this study was to evaluate retinal arteriolar parameters using the rtx1 adaptive optics fundus camera (AO-FC) in patients with primary open-angle glaucoma (POAG) at different stages and to investigate the relationship between these parameters and changes in spectral-domain optical coherence tomography (SD-OCT) and perimetry.

METHODS

Parameters of the retinal supratemporal and infratemporal arterioles (wall thickness (WT), lumen diameter (LD), total diameter (TD), wall-to-lumen ratio (WLR), and cross-sectional area of the vascular wall (WCSA)) were analysed with the rtx1 in 111 POAG eyes, which were divided into three groups according to the severity of the disease, and 70 healthy eyes. The associations between RTX1 values and the cup-to-disk ratio, SD-OCT parameters, and visual field parameters were assessed.

RESULTS

Compared with the control group, the POAG groups showed significantly smaller TD and LD values (p < 0.05) and significantly higher WLR and WT values (p < 0.05) for the supratemporal and infratemporal arterioles. TD was significantly positively correlated with the retinal nerve fibre layer (RNFL) and ganglion cell complex (GCC) (p < 0.05). LD was significantly positively correlated with the RNFL, GCC, and rim area (p < 0.05). The WLR was significantly negatively correlated with the RNFL, GCC, rim area, and MD (p < 0.05), while it was significantly positively correlated with the cup-to-disc ratio and PSD (p < 0.05).

CONCLUSIONS

The results suggest that vascular dysfunction is present in POAG, even at a very early stage of glaucoma, and increases with the severity of the disease.

Peripapillary vessel density in healthy people, primary open-angle glaucoma, and normal-tension glaucoma

OBJECTIVE

To compare peripapillary vessel density using optical coherence tomography angiography (OCT-A) in eyes of healthy people, primary open-angle glaucoma (POAG), and normal-tension glaucoma (NTG).

METHODS

Thirty patients with POAG, 27 patients with NTG, and 29 healthy individuals in the control group were assessed. Capillary vessels in peripapillary retinal nerve fiber layer (RNFL) represented by whole image RPC (radial peripapillary capillary) density in an AngioDisc scan 4.5 × 4.5 mm centered on the optic disc, and ONH morphological variables (disc area, rim area, cup to disc area ratio (CDR)), and average peripapillary RNFL thickness were measured.

RESULTS

Differences in mean RPC, RNFL, disc area, rim area, and CDR between the groups were statistically significant (P < 0.05). The difference in RNFL thickness and rim area was not significant between NTG and healthy groups, while RPC and CDR showed a statistically significant difference between all pairs. The vessel density in the POAG group was 8.25% and 11.7% lower compared to the NTG and healthy groups, respectively; while the mean difference was less (2.97%) for the NTG and healthy group. In the POAG group, 67.2% of the variation in RPC can be explained by a model containing CDR and RNFL thickness, and in normal eyes 38.8% of the changes using a model containing RNFL.

CONCLUSION

The peripapillary vessel density is reduced in both types of glaucoma. The vessel density in NTG was significantly lower than in the healthy eyes, despite the lack of significant difference in RNFL thickness and neuroretinal rim area between them.

Comparison of the Choroid in Primary Open Angle and Angle Closure Glaucoma Using Optical Coherence Tomography

PRCIS

The current study highlights distinct choroidal alterations in primary open angle (POAG) and primary angle closure (PACG) glaucomas, underscoring the potential of the Choroidal Vascularity Index (CVI) as a valuable indicator for understanding glaucoma pathogenesis.

PURPOSE

To evaluate choroidal structural changes in patients with POAG and PACG and healthy controls utilizing the CVI and subfoveal choroidal thickness by enhanced depth imaging optical coherence tomography.

METHODS

This study was cross-sectional. A total of 171 eyes of 171 subjects, comprising 69 eyes with untreated POAG, 58 eyes with untreated PACG, and 44 healthy eyes, were enrolled in this study. Subfoveal choroidal thickness, luminal area (LA), stromal area (SA), and total choroidal area were measured on enhanced depth imaging-optical coherence tomography scans. The CVI parameter is calculated as the proportion of LA to the total choroidal area.

RESULTS

This study included 69 patients with POAG with a mean age of 51.4 ± 13.3 years, 58 patients with PACG with a mean age of 57.0 ± 7.3 years, and 44 healthy subjects with a mean age of 51.11 ± 10.7 years. The CVI in the POAG and PACG groups was significantly lower than that in the control group ( P = 0.001 and P = 0.005, respectively); however, not significantly different between the two glaucoma groups ( P = 1.000). POAG eyes had significantly lower LA than PACG and controls ( P = 0.014 and P = 0.049, respectively), whereas PACG eyes had significantly greater SA than controls ( P = 0.041).

CONCLUSIONS

The CVI of POAG and PACG eyes was significantly lower than that of normal eyes. A reduced LA was observed mainly in eyes with POAG, and an increased SA was observed mainly in eyes with PACG. The role of the choroid may differ between POAG and PACG eyes.

Quantification of vascular morphology in optical coherence tomography angiography in primary open angle glaucoma

Purpose

To quantitatively measure and compare the vascular morphology in healthy eyes and eyes with primary open-angle glaucoma (POAG) using optical coherence tomography angiography (OCTA) scans.

Methods

This is a retrospective and cross-sectional study which include healthy individuals and individuals with POAG that underwent OCTA imaging at an academic center's glaucoma clinic. We analyzed OCTA scans of the macula and optic nerve head (ONH) of one eye from each subject to quantitatively measure vessel density (VD), vessel length density (VLD), and branchpoint density (BPD). We compared these 3 parameters between the healthy and POAG groups and used logistic regression classification models to determine their diagnostic value in differentiating healthy and glaucomatous eyes.

Results

We included 49 healthy subjects and 49 subjects with POAG. After age-adjusted analysis, the parameters of VD, VLD, and BPD were significantly reduced in eyes with POAG (P ​< ​0.001) in all scan layers and most significantly around the ONH. The parameter with the best performances were radial peripapillary capillary (RPC) VD [AUC (areas under the curve): 0.939 (0.891, 0.987)] which had statistically higher performances (P ​< ​0.05) than parameters in the superficial or deep layers. All 3 parameters in the RPC layer had statistically similar performances.

Conclusions

We found that VD, VLD, and BPD were reduced in glaucomatous eyes. The morphologic parameters of VLD and BPD had similar performances to the traditional parameter of VD in RPC layers. Our results suggest that vascular morphology parameters may provide additional value in the diagnosis and evaluation of glaucoma.

The Differences in the Pattern of OCT and OCTA Examinations between Early Normal- and High-Tension Pseudoexfoliative Glaucoma

Purpose. The aim of this study was to compare the results of optical coherence tomography angiography (OCTA) and optical coherence tomography (OCT) examinations in patients with normal-tension glaucoma (NTG) in comparison to high-tension pseudoexfoliative glaucoma (HTG) patients at the early stage of glaucoma. Material and methods. The studied groups consisted of patients in the early stage of NTG (70 eyes) and the early stage of HTG (71 eyes). In NTG and HTG groups, a detailed ophthalmic examination was performed. Optic disc OCT with peripapillary RNFL measurements and OCTA examination with the evaluation of the macula and optic disc were performed for all participants using Zeiss Cirrus 5000. Results. NTG and HTG groups were statistically similar as far as the MD was concerned, and both groups had early glaucoma. When evaluating the RNFL thickness, the only statistical difference between early NTG and HTG was observed in the thicknesses in the temporal sector of peripapillary RNFL, with thinner values in the NTG group (53.94 vs. 59.94, p = 0.0071). When the OCTA results of the macula and optic disc were evaluated, there were no statistical differences between early NTG and HTG. Conclusions. The vascular density and flow parameters assessed in OCTA were equal between early NTG and HTG, and therefore the involvement of vascular factors in NTG pathogenesis could not be confirmed. Our results confirm the preponderance of more frequent temporal RNFL involvement in early NTG.

Risk of Normal Tension Glaucoma Progression From Automated Baseline Retinal-Vessel Caliber Analysis: A Prospective Cohort Study

PURPOSE

To determine the relationship between baseline retinal-vessel calibers computed by a deep-learning system and the risk of normal tension glaucoma (NTG) progression.

DESIGN

Prospective cohort study.

METHODS

Three hundred and ninety eyes from 197 patients with NTG were followed up for at least 24 months. Retinal-vessel calibers (central retinal arteriolar equivalent [CRAE] and central retinal venular equivalent [CRVE]) were computed from fundus photographs at baseline using a previously validated deep-learning system. Retinal nerve fiber layer (RNFL) thickness and visual field (VF) were evaluated semiannually. The Cox proportional-hazards model was used to evaluate the relationship of baseline retinal-vessel calibers to the risk of glaucoma progression.

RESULTS

Over a mean follow-up period of 34.36 ± 5.88 months, 69 NTG eyes (17.69%) developed progressive RNFL thinning and 22 eyes (5.64%) developed VF deterioration. In the multivariable Cox regression analysis adjusting for age, gender, intraocular pressure, mean ocular perfusion pressure, systolic blood pressure, axial length, standard automated perimetry mean deviation, and RNFL thickness, narrower baseline CRAE (hazard ratio per SD decrease [95% confidence interval], 1.36 [1.01-1.82]) and CRVE (1.35 [1.01-1.80]) were associated with progressive RNFL thinning and narrower baseline CRAE (1.98 [1.17-3.35]) was associated with VF deterioration.

CONCLUSION

In this study, each SD decrease in the baseline CRAE or CRVE was associated with a more than 30% increase in the risk of progressive RNFL thinning and a more than 90% increase in the risk of VF deterioration during the follow-up period. Baseline attenuation of retinal vasculature in NTG eyes was associated with subsequent glaucoma progression. High-throughput deep-learning-based retinal vasculature analysis demonstrated its clinical utility for NTG risk assessment.

Deep Learning in Optical Coherence Tomography Angiography: Current Progress, Challenges, and Future Directions

Optical coherence tomography angiography (OCT-A) provides depth-resolved visualization of the retinal microvasculature without intravenous dye injection. It facilitates investigations of various retinal vascular diseases and glaucoma by assessment of qualitative and quantitative microvascular changes in the different retinal layers and radial peripapillary layer non-invasively, individually, and efficiently. Deep learning (DL), a subset of artificial intelligence (AI) based on deep neural networks, has been applied in OCT-A image analysis in recent years and achieved good performance for different tasks, such as image quality control, segmentation, and classification. DL technologies have further facilitated the potential implementation of OCT-A in eye clinics in an automated and efficient manner and enhanced its clinical values for detecting and evaluating various vascular retinopathies. Nevertheless, the deployment of this combination in real-world clinics is still in the "proof-of-concept" stage due to several limitations, such as small training sample size, lack of standardized data preprocessing, insufficient testing in external datasets, and absence of standardized results interpretation. In this review, we introduce the existing applications of DL in OCT-A, summarize the potential challenges of the clinical deployment, and discuss future research directions.

Ocular Factors of Fractal Dimension and Blood Vessel Tortuosity Derived From OCTA in a Healthy Chinese Population

Purpose

To identify the ocular factors of microvascular fractal dimension (FD) and blood vessel tortuosity (BVT) of macula measured with optical coherence tomography angiography (OCTA) in a healthy Chinese population.

Methods

Healthy subjects without ocular disorders were recruited at Zhongshan Ophthalmic Center. The FD and BVT in the superficial capillary plexus (SCP) and deep capillary plexus (DCP) at the macula were obtained from OCTA images. The FD was calculated using the box-counting method, and the BVT was defined as the ratio of the actual distance between two points to the straight distance on the skeletonized image. Univariate and stepwise multivariate linear regression analyses were performed to identify the ocular factors of FD and BVT, and the results are presented as coefficients and 95% confidence intervals (CIs). Only the right eye of each subject was included.

Results

A total of 2189 healthy individuals (2189 eyes) were included with a mean age of 49.9 ± 13.2 years; 54.4% were female. In the multivariate model, the FD in the SCP was significantly associated with higher intraocular pressure (IOP) (β = 0.204; 95% CI, 0.073-0.335; P < 0.001), axial length (AL) (β = -0.875; 95% CI, -1.197 to -0.552; P < 0.001; R2 = 0.26; root mean square error [RMSE] = 7.78). The FD in the DCP was significantly associated with best-corrected visual acuity (β = -6.170; 95% CI, -10.175 to -2.166; P = 0.003) and anterior chamber depth (β = -0.348; 95% CI, -0.673 to -0.023; P = 0.036; R2 = 0.10; RMSE = 2.58). Superficial BVT was independently associated with IOP (β = -0.044; 95% CI, -0.079 to -0.009; P = 0.012) and AL (β = 0.097; 95% CI, 0.014-0.181; P = 0.022; R2 = 0.15; RMSE = 2.02). Deep BVT was independently associated with IOP (β = -0.004; 95% CI, -0.009 to -0.0005; P = 0.028) and lens thickness (β = 0.036, 95% CI, 0.003-0.060; P = 0.028; R2 = 0.07, RMSE = 0.25).

Conclusions

The IOP and AL were dependent ocular parameters variables of FD and BVT in the SCP in this healthy population. The FD in the DCP was also influenced by visual acuity and anterior chamber depth. These factors should be considered when microvascular geometrics are used in the future studies.

Translational Relevance

This work discovered the influence factors of OCTA geometrics parameters for further establishment of diagnostic model or method for glaucoma and other microvasculature-related ocular diseases.

Optical Coherence Tomography Angiography in Posner-Schlossman Syndrome - A Preliminary Study

PURPOSE

To evaluate vessel density (VD) and structural features in Posner-Schlossman syndrome (PSS) patients' eyes using optical coherence tomography angiography (OCTA).

METHODS

An observational study was conducted among 23 affected eyes (group A), 23 contralateral unaffected eyes (group B), and 23 control eyes (group C).

RESULT

The macular superficial, macular deep, and optic nerve head (ONH) VD of group A were 45.26 ± 5.80, 46.78 ± 6.96, and 46.10 ± 4.22, respectively. The macular superficial VD, macular deep VD, and retinal thickness of group A were significantly lower than those of group C (all P < .05). The retinal nerve fiber layer thickness of group A decreased in the superior and inferior sections. The macular superficial VD had the highest diagnostic value (area under curve = 0.989) for PSS.

CONCLUSION

OCTA can detect the fundus change in the macular and ONH regions of the PSS's affected eyes.

Normal-tension glaucoma: Current concepts and approaches-A review

Normal tension glaucoma (NTG) has remained a challenging disease. We review, from an epidemiological perspective, why we should redefine normality, act earlier at lower pre-treatment intraocular pressure (IOP) level, and the role of ocular perfusion pressures, noting that perfusion is affected by defective vascular bed autoregulation and endothelial dysfunction. The correlation of silent cerebral infarcts (SCI) and NTG may indicate that NTG belongs to a wider spectrum of small vessel diseases (SVD), with its main pathology being also on vascular endothelium. Epidemiological studies also suggested that vascular geometry, such as fractal dimension, may affect perfusion efficiency, occurrence of SCI, SVD and glaucoma. Artificial intelligence with deep learning, may help predicting NTG progression from vascular geometry. Finally, we review latest evidence on the role of minimally-invasive glaucoma surgery, lasers, and newer drugs. We conclude that IOP is not the only modifiable risk factors as, many vascular risk factors are readily modifiable.

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.

Characterization of macular choroid in normal-tension glaucoma: a swept-source optical coherence tomography study

PURPOSE

To investigate the features of the small-to-medium (choriocapillaris and Sattler's layer) and large (Haller's layer) sized vessel layers of the macular choroid in normal-tension glaucoma (NTG) patients using swept-source optical coherence tomography (SS-OCT).

METHODS

We conducted an observational cross-sectional study in 234 NTG eyes from 134 patients, and 203 normal eyes from 109 non-glaucomatous control subjects. We used Image J to segment the choroidal layer and then a Python script to measure the average macular choroidal thickness (MCT) and choroidal vascular index (CVI) of two vessel layers at five different locations. Quantitative optical coherence tomography angiography (OCTA) metrics for the superficial capillary plexus (SCP) and deep capillary plexus (DCP) at macular region were also measured by a customized MATLAB program. Generalized estimating equations (GEE) models were performed to determine ocular and demographic factors associated with the choroidal metrics, adjusting for inter-eye correlation.

RESULTS

Significant average MCT thinning was found in NTG eyes at all five locations of the two layers, in comparison with controls (all p ≤ 0.05). In addition, compared with control eyes, significant decrease in CVI was found in NTG eyes at all five sections of the large sized vessel layer: 500 µm nasal and temporal to macula (p = 0.002), 1500 µm nasal (p < 0.001), 2500 µm nasal (p = 0.001), 1500 µm temporal (p < 0.001) and 2500 µm temporal (p = 0.004). In contrast, no significant CVI difference was detected in the small-to-medium sized vessel layer. In the comparison of OCTA metrics of SCP and DCP at macular region between NTG and normal eyes, there were no significant difference of parafoveal vessel density (VD), foveal avascular zone (FAZ) area, FAZ circularity and fractal dimension (FD) in both layers.

CONCLUSION

We found significant alterations in macular choroidal vascularity (reduced CVI and thinner layer) in NTG patients. Such alterations are more pronounced in the Haller's layer, rather than the choriocapillaris & Sattler's layer, in NTG. Choroidal layer may be more related to vasculature changes at macular region in NTG.