Retinal vessel phenotype in patients with primary open-angle glaucoma

Prevalence and Risk Factors of Fundus Pathology in Patients with Type 2 Diabetes in a Northeastern Chinese Cohort

PURPOSE

To assess the prevalence of and risk factors for fundus pathology in patients with type 2 diabetes mellitus (T2DM) in a cohort from northeastern China.

METHODS

Patients were included from the Fushun Diabetic Retinopathy Cohort Study. Patients aged ≥ 30 years with T2DM were recruited between July 2012 and May 2013. Fundus pathology included retinal vascular occlusion (RVO), age-related macular degeneration (AMD), macular pathology, pathologic myopia (PM) and glaucomatous optic atrophy (GOA).

RESULTS

A Total of 1998 patients with gradable fundus photographs were included in this study, of whom 388 (19.42%) had fundus pathology regardless of whether they had diabetic retinopathy (DR). There were 187 (9.36%) patients with AMD, 97 (4.85%) with GOA, 67 (3.35%) with macular pathology, 35 (1.75%) with PM and 23 (1.15%) with RVO. Advanced age was significantly associated with AMD (odds ratio (OR), 95% confidence interval (CI): 1.03, 1.01-1.05), macular pathology (OR, 95% CI: 1.06, 1.03-1.09) and GOA (OR, 95% CI: 1.06, 1.04-1.09). A wider central retinal arteriolar equivalent was protective against PM (OR, 95% CI: 0.78, 0.66-0.92). Wider central retinal venular equivalent was a protective factor for PM (OR, 95% CI: 0.75, 0.68-0.82) and GOA (OR, 95% CI: 0.93, 0.87-0.99).

CONCLUSIONS

One-fifth of these patients in northeast China with T2DM had fundus pathology regardless of whether they had DR, indicating the importance of early screening and long-term follow-up.

High-intensity interval training in patients with glaucoma (HIT-GLAUCOMA): protocol for a multicenter randomized controlled exercise trial

Background

Glaucoma stands as a prominent global cause of irreversible blindness and the primary treatment approach involves reducing intraocular pressure (IOP). However, around one-third of patients exhibit disease progression despite effective IOP reduction. Microvascular endothelial function, chronic inflammation, and oxidative stress are known to affect retinal neuronal networks and have been associated with disease severity and progression. Exercise training has the potential to counteract these mechanisms as add-on treatment to usual care.

Aims

The HIT-GLAUCOMA study will investigate the effects of a 6-month high-intensity interval training (HIIT) on intermediate endpoints such as local retinal microvascular and systemic large artery function, inflammation, and oxidative stress as well as clinical endpoints such as visual field indices, optic nerve rim assessment, retinal nerve fiber layer thickness, IOP, number of eye drops, vision-related quality of life and ocular surface disease symptomatology.

Methods

The study is a multi-center randomized controlled clinical trial in patients with both normal tension and high-tension primary open angle glaucoma. Across two study centers, 128 patients will be enrolled and randomized on a 1:1 basis into an exercise intervention group and a usual care control group. The primary microvascular endpoints are retinal arteriolar and venular flicker light-induced dilation at 6 months. The primary endpoint in the systemic circulation is brachial artery flow-mediated dilation at 6 months.

Anticipated results

We hypothesize that exercise therapy will improve retinal microvascular function and thus ocular blood flow in patients with glaucoma. As clinical outcomes, we will investigate the effect of exercise on visual field indices, optic nerve rim assessment, retinal nerve fiber layer thickness, IOP, number of eye drops, vision-related quality of life and ocular surface disease symptomatology.

Discussion

HIT-GLAUCOMA is a blueprint trial design to study the effect of exercise training on neurodegenerative and cardiovascular diseases. Importantly, patients are also expected to benefit from improvements in general health and cardiovascular co-morbidities. If proven effective, exercise may offer a new add-on treatment strategy to slow glaucoma progression.

Clinical Trial Registration Number

The trial is registered at Clinicaltrials.gov under the identifier NCT06058598 and is currently in the recruitment stage.

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.

Retinal vessel architecture and geometry are not impaired in normal-tension glaucoma

To investigate the associations between retinal vessel parameters and normal-tension glaucoma (NTG). We conducted a case-control study with a prospective cohort, allowing to record 23 cases of NTG. We matched NTG patient with one primary open-angle glaucoma (POAG) and one control per case by age, systemic hypertension, diabetes, and refraction. Central retinal artery equivalent (CRAE), central retinal venule equivalent (CRVE), Arteriole-To-Venule ratio (AVR), Fractal Dimension and tortuosity of the vascular network were measured using VAMPIRE software. Our sample consisted of 23 NTG, 23 POAG, and 23 control individuals, with a median age of 65 years (25-75th percentile, 56-74). No significant differences were observed in median values for CRAE (130.6 µm (25-75th percentile, 122.8; 137.0) for NTG, 128.4 µm (124.0; 132.9) for POAG, and 135.3 µm (123.3; 144.8) for controls, P = .23), CRVE (172.1 µm (160.0; 188.3), 172.8 µm (163.3; 181.6), and 175.9 µm (167.6; 188.4), P = .43), AVR (0.76, 0.75, 0.74, P = .71), tortuosity and fractal parameters across study groups. Vascular morphological parameters were not significantly associated with retinal nerve fiber layer thickness or mean deviation for the NTG and POAG groups. Our results suggest that vascular dysregulation in NTG does not modify the architecture and geometry of the retinal vessel network.

Using Artificial Intelligence to Analyse the Retinal Vascular Network: The Future of Cardiovascular Risk Assessment Based on Oculomics? A Narrative Review

The healthcare burden of cardiovascular diseases remains a major issue worldwide. Understanding the underlying mechanisms and improving identification of people with a higher risk profile of systemic vascular disease through noninvasive examinations is crucial. In ophthalmology, retinal vascular network imaging is simple and noninvasive and can provide in vivo information of the microstructure and vascular health. For more than 10 years, different research teams have been working on developing software to enable automatic analysis of the retinal vascular network from different imaging techniques (retinal fundus photographs, OCT angiography, adaptive optics, etc.) and to provide a description of the geometric characteristics of its arterial and venous components. Thus, the structure of retinal vessels could be considered a witness of the systemic vascular status. A new approach called "oculomics" using retinal image datasets and artificial intelligence algorithms recently increased the interest in retinal microvascular biomarkers. Despite the large volume of associated research, the role of retinal biomarkers in the screening, monitoring, or prediction of systemic vascular disease remains uncertain. A PubMed search was conducted until August 2022 and yielded relevant peer-reviewed articles based on a set of inclusion criteria. This literature review is intended to summarize the state of the art in oculomics and cardiovascular disease research.

Lower fractal dimension of retinal vessel for patients with Birdshot chorioretinopathy

PURPOSE

To identify the retinal vessel vasculature parameters associated with birdshot chorioretinopathy (BSCR).

METHODS

This retrospective observational study included 28 prevalent cases of BSCR with a median time from diagnosis of 6 years and 28 controls matched for age, arterial hypertension, diabetes and refraction. Forty-five-degree fundus images of both dilated eyes were acquired with a fundus camera (Canon CR-2, Tokyo, Japan). The summary diameter of the arterial retinal vessels (central retinal artery equivalent, CRAE), venous retinal vessels (central retinal vein equivalent, CRVE), vascular tortuosity and fractal dimension (FD) were measured using VAMPIRE software. Retinal vasculitis was characterized using fluorescein angiography and active choroiditis using indocyanine green angiography.

RESULTS

At baseline, BSCR was associated with lower FD compared with matched controls (mean difference, -0.04; 95% confidence interval [CI], -0.06 to -0.02, p < 0.001). No other VAMPIRE parameters (CRAE, CRVE, arterial and venous tortuosity) differed. Among BSCR patients, retinal vein vasculitis was associated with higher CRAE (mean difference, 21 μ; 95% CI, 2.6-40, p = 0.03), venous tortuosity (geometric mean ratio, 1.79; 95% CI, 1.18-2.72, p = 0.007) and FD (mean difference, -0.04; 95% CI, -0.06 to -0.01, p = 0.007). Resolution of retinal vein vasculitis during follow-up was paralleled by decrease in CRAE, CRVE and venous tortuosity values and increase in venous FD, respectively.

CONCLUSION

BSCR is associated with lower FD value, suggesting that chronic retinal inflammation induces microvascular remodelling. Efficient treatment of retinal vasculitis may reverse changes in retinal vascular parameters. Changes in retinal vascular parameters could be potentially useful for assessing patients with BSCR disease.

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.

Asian Race and Primary Open-Angle Glaucoma: Where Do We Stand?

Primary open-angle glaucoma (POAG) is an optic neuropathy characterized by irreversible retinal ganglion cell damage and visual field loss. The global POAG prevalence is estimated to be 3.05%, and near term is expected to significantly rise, especially within aging Asian populations. Primary angle-closure glaucoma disproportionately affects Asians, with up to four times greater prevalence of normal-tension glaucoma reported compared with high-tension glaucoma. Estimates for overall POAG prevalence in Asian populations vary, with Chinese and Indian populations representing the majority of future cases. Structural characteristics associated with glaucoma progression including the optic nerve head, retina, and cornea are distinct in Asians, serving as intermediates between African and European descent populations. Patterns in IOP suggest some similarities between races, with a significant inverse relationship between age and IOP only in Asian populations. Genetic differences have been suggested to play a role in these differences, however, a clear genetic pattern is yet to be established. POAG pathogenesis differs between Asians and other ethnicities, and it may differ within the broad classification of the Asian race. Greater awareness and further research are needed to improve treatment plans and outcomes for the increasingly high prevalence of normal tension glaucoma within aging Asian populations.

Retinal Vessel Phenotype in Patients with a History of Retinal Vein Occlusion

INTRODUCTION

The aim of the study was to estimate the phenotype of retinal vessels using central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), tortuosity, and fractal analysis in the unaffected contralateral eye of patients with central or branch retinal vein occlusion (CRVO or BRVO).

METHODS

Thirty-four patients suffering from CRVO, 15 suffering from BRVO, and 49 controlled matched subjects had a fundus image analyzed using the VAMPIRE software. The intraclass correlation coefficient and a Bland-Altman plot were done for the reproducibility study.

RESULTS

There was a lack of evidence of difference between the control group and the CRVO group for CRAE (p = 0.06), CRVE (p = 0.3), and arterio-venule ratio (AVR, p = 0.6). Contralateral eyes of CRVO exhibited a significantly higher arterial and minimum arterial tortuosity values (p = 0.012), as compared with control eyes. Contralateral eyes of patients with a history of BRVO had a significantly higher CRAE (p = 0.02), AVR (p = 0.006), and minimal arterial tortuosity (p = 0.05). Fractal analysis showed that contralateral eyes of BRVO had higher values of fractal parameters (D0a, p = 0.005).

CONCLUSION

This study suggests that CVRO or BRVO is not triggered by the same retinal vascular phenotypes in the contralateral eye. The morphology of retinal vasculature may be associated with the occurrence of RVO, independently of known risk factors.

Association between Systemic Antioxidant Capacity and Retinal Vessel Diameters in Patients with Primary-Open Angle Glaucoma

The retinal vessel narrowing may be implicated in the pathogenesis of glaucoma; however, the association between systemic oxidative stress and retinal vessel diameter remains largely unknown. We examined the relationship between serum oxidative stress markers and retinal vessel diameters in eyes with primary open-angle glaucoma (POAG) and cataract, using central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE). We included 66 eyes of 66 patients with POAG (37 men, 29 women; 65.4 ± 11.7 years) and 20 eyes of 20 patients with cataract (7 men, 13 women; 69.4 ± 9.0 years) as the controls. The CRAE (p < 0.0001), CRVE (p < 0.0001), and serum biological antioxidant potential (BAP) (p = 0.0419) were significantly lower in the POAG group compared to the controls. The BAP showed significant correlation both with CRAE (ρ = 0.2148, p = 0.0471) and systolic blood pressure (ρ = −0.2431, p = 0.0241), while neither Diacron reactive oxygen metabolites nor sulfhydryl test correlated with them. The multivariate analyses indicated that age, best corrected visual acuity, and BAP were independent factors for CRAE or CRVE. The present study suggested that lower systemic antioxidant capacity was significantly associated with the intraocular pressure-independent vascular narrowing in POAG patients. This study provided a novel insight into the pathophysiology of glaucoma and highlighted the clinical impact on systemic antioxidant treatment for patients with glaucoma.