Ocular Perfusion Pressure and Severity of Glaucoma: Is There a Link?

The impact of intraocular pressure fluctuations on the progression of glaucoma and associated factors

Background

In recent years, remarkable advancements in the comprehension of glaucoma pathophysiology have highlighted the necessity of looking beyond the conventional focus on mean intraocular pressure (IOP) levels. IOP fluctuations have been identified as a potential factor that could exert a substantial impact on the progression of glaucoma.

Main text

IOP exhibits dynamic variations throughout a 24-h cycle. Glaucoma patients exhibit substantially more pronounced IOP fluctuations compared to healthy individuals, even when the mean IOP remains within the normal range. This implies that IOP fluctuations may play a role in glaucoma progression through mechanisms independent of elevated mean IOP. In this review, an exhaustive examination of studies spanning the past decade was conducted to analyze the relationship between IOP fluctuations and disease progression in primary open-angle glaucoma (POAG), ocular hypertension (OHT), normal tension glaucoma (NTG), and primary angle-closure glaucoma (PACG). While a few studies present conflicting results, the majority of research supports the notion that elevated IOP fluctuations significantly contribute to disease progression in POAG patients. This association has also been confirmed in PACG patients. However, in NTG or OHT patients, other risk factors may outweigh IOP fluctuations in disease progression or glaucoma conversion. Additionally, we summarized common factors affecting IOP fluctuations to provide a basis for the identification of patients prone to significant daily IOP variations. Finally, the efficacy of various IOP-lowering interventions in modulating IOP fluctuations is concisely summarized, offering insights for the formulation of comprehensive treatment strategies that incorporate IOP fluctuation management.

Conclusions

IOP fluctuations play a significant role in disease progression in POAG and PACG. Individuals with certain systemic or ocular characteristics are more predisposed to pronounced and recurrent IOP fluctuations. Consequently, a comprehensive assessment of IOP fluctuation that transcends mean IOP values, as well as the integration of IOP fluctuations management into glaucoma treatment strategies are of paramount importance.

The strong correlation between visual function improvement and retinal microcirculation enhancement in glaucoma

Introduction

This study aimed to investigate the alterations in retinal vessel density (VD) among glaucomatous patients following effective intraocular pressure (IOP) reduction and to explore the relationship between retinal VD, visual function, and optic nerve structure.

Methods

Participants diagnosed with primary open-angle glaucoma (POAG) and chronic primary angle-closure glaucoma (CPACG) were included. We measured peripapillary and macular VD, retinal nerve fiber layer (RNFL) thickness, foveal avascular zone (FAZ), and visual field (VF) parameters before treatment, and at 1 week, 1 month, 3 months, and 6 months post-treatment. The data were analyzed using ANOVA and Pearson correlation analysis.

Results

A total of 20 patients were included. Significant improvements in peripapillary VD were observed in the superior and nasal sectors at 1 week, superior and temporal sectors at 1 month, and in the superior, inferior, and temporal sectors at 3 months, with sustained improvements in the superior, nasal, and temporal sectors at 6 months. Recovery of macular VD was noted across all sectors at 1 week, predominantly in the superior parafovea at 1 month, and in the superior, inferior parafovea, and inferior perifovea by 3 months, with further improvement in the inferior parafovea and perifovea at 6 months. The FAZ area significantly narrowed within the first 3 months. The mean deviation (MD) value demonstrated an increase at 1 week, 3 months, and 6 months. Notably, changes in peripapillary VD in the superior and inferior sectors exhibited a strong correlation with MD values, while correlations in the nasal and temporal sectors were moderate. Conversely, the correlation between IOP changes and MD was weak.

Discussion

Effective IOP reduction was beneficial for the recovery of both peripapillary and macular microcirculation, leading to improvements in visual function, suggesting that actively improving retinal microcirculation while reducing IOP may contribute to partial recovery of visual function for patients with chronic glaucoma.

Evaluating the impact of caloric restriction, body mass index and exercise on primary open-angle glaucoma: A review

This literature review evaluates any possible links between primary open-angle glaucoma (POAG) and caloric restriction (CR), body mass index (BMI), and exercise, aiming to map the extent of the literature. Its primary objective is to recognise the nature and breadth of research evidence, identify possible gaps in these topics and develop future studies. The databases searched were MEDLINE (PudMed), Scopus and ScienceDirect, in April 2023 for articles published in English, with no date restriction. A total of 447 search results were retrieved. Of these, 73 were related to CR, 249 to BMI, and 125 to exercise. Records identified included systematic reviews, meta-analyses, randomised controlled trials, cohort studies and animal studies. CR has been shown to halt the degeneration of retinal ganglion cells and protect against various glaucomatous processes in animal models. Low BMI has been shown to be associated with an increased risk of POAG and a faster rate of visual field deterioration in POAG. However, the association between high BMI and POAG is not consistent. Exercise has been shown to cause mechanical, vascular, and neurobiological changes affecting the pathophysiology of POAG. The present review helps identify key characteristics and factors relating to the impacts of CR, BMI, or exercise on POAG.

Long-Term Blood Pressure Variability and Visual Field Progression in Glaucoma

Importance

Long-term variability of blood pressure may be associated with visual field (VF) progression in patients with glaucoma.

Objectives

To investigate the association between blood pressure parameters and VF progression over time in patients with glaucoma.

Design, Setting, and Participants

This retrospective cohort study of longitudinal data included patients with suspected or confirmed glaucoma who were selected from the Diagnostic Innovations in Glaucoma Study and the African Descent and Glaucoma Evaluation Study. Patients underwent blood pressure and VF testing from November 2000 to December 2022, and data were analyzed in October 2023.

Exposure

Suspected or confirmed glaucoma.

Main Outcomes and Measures

Mean and SD values of blood pressure variables were calculated for systolic and diastolic arterial pressures. These parameters were incorporated into multivariable mixed-effect models to investigate the association between blood pressure parameters and mean intraocular pressure with rates of VF mean deviation loss. Interaction terms between blood pressure parameters and mean intraocular pressure were also included in the models.

Results

A total of 1674 eyes from 985 patients were assessed (mean [SD] age, 61.2 [0.4] years; 563 female [57.2%]). The mean rate of VF mean deviation change was -0.13 (95% CI, -0.16 to -0.10) dB/y over a mean follow-up of 8.0 (95% CI, 7.7-8.2) years. The interaction terms of higher mean blood pressure and higher SD of blood pressure were associated with faster annual mean deviation changes for both mean arterial pressure (0.02 [95% CI, 0.01-0.04] dB/y per 1-mm Hg higher; P = .001) and diastolic arterial pressure (0.02 [95% CI, 0.01-0.03] dB/y per 1-mm Hg higher; P < .001). The interaction term of higher SD of blood pressure and higher mean intraocular pressure was associated with faster annual mean deviation changes for both mean arterial pressure (0.01 [95% CI, 0.00-0.02] μm per 1-mm Hg higher; P = .003) and diastolic arterial pressure (0.01 [95% CI, 0.00-0.01] μm per 1-mm Hg higher; P = .001).

Conclusions and Relevance

In this cohort study, higher mean blood pressure and higher SD of blood pressure were associated with faster VF progression. These findings suggest that long-term variability of blood pressure may be a modifier of the association between intraocular pressure and VF progression in glaucoma.

Color Doppler Imaging Assessment of Ocular Blood Flow Following Ab Externo Canaloplasty in Primary Open-Angle Glaucoma

Background/Objectives: Glaucomatous neuropathy, a progressive deterioration of retinal ganglion cells, is the leading cause of irreversible blindness worldwide. While elevated intraocular pressure (IOP) is a well-established modifiable risk factor, increasing attention is being directed towards IOP-independent factors, such as vascular alterations. Color Doppler imaging (CDI) is a prominent technique for investigating blood flow parameters in extraocular vessels. This prospective, nonrandomized clinical trial aimed to assess the impact of ab externo canaloplasty on ocular blood flow parameters in patients with primary open-angle glaucoma (POAG) at a three-month follow-up. Methods: Twenty-five eyes of twenty-five patients with early or moderate POAG underwent canaloplasty with simultaneous cataract removal. CDI was used to measure peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI) in the ophthalmic artery (OA), central retinal artery (CRA), and short posterior ciliary arteries (SPCAs) before and after surgery. Results: The results showed a significant reduction in IOP and improvement in mean deviation at three months post-surgery. Best corrected visual acuity and retinal nerve fiber layer thickness significantly increased at each postoperative control visit. However, no significant changes were observed in PSV, EDV, and RI in the studied vessels. Conclusions: In conclusion, while canaloplasty effectively reduced IOP and medication burden, it did not significantly improve blood flow parameters in vessels supplying the optic nerve at three months post-surgery. Careful patient selection considering glaucoma severity and vascular risk factors is crucial when choosing between canaloplasty and more invasive procedures like trabeculectomy. Further larger studies are needed to comprehensively analyze this issue.

Optic Nerve Head Pulsatile Displacement in Open-Angle Glaucoma after Intraocular Pressure Reduction Measured by Optical Coherence Tomography: A Pilot Study

This study investigated the effect of intraocular pressure (IOP) reduction on pulsatile displacement within the optic nerve head (ONH) in primary open-angle glaucoma (POAG) patients with and without axial myopia. Forty-one POAG patients (19 without myopia, 9 with axial myopia and 13 glaucoma with no intervention) participated. Swept-source optical coherence tomography (OCT) videos of the ONH were obtained before and after IOP-lowering treatment (medical or surgical) achieving a minimum IOP drop of 3 mmHg. A demons registration-based algorithm measured local pulsatile displacement maps within the ONH. Results demonstrated a significant 14% decrease in pulsatile tissue displacement in the non-myopic glaucoma cohort after intervention (p = 0.03). However, glaucoma patients with axial myopia exhibited no statistically significant change. There were no significant changes in the pulsatile ONH deformation in the control group. These findings suggest a potential link between IOP reduction and reduced pulsatile displacement within the ONH in POAG patients without myopia, offering new insights into the disease's pathophysiology and warranting further investigation into underlying mechanisms and clinical implications.

The Relevance of Arterial Blood Pressure in the Management of Glaucoma Progression: A Systematic Review

BACKGROUND

Glaucoma is one of the leading causes of global blindness and is expected to co-occur more frequently with vascular morbidities in the upcoming years, as both are aging-related diseases. Yet, the pathogenesis of glaucoma is not entirely elucidated and the interplay between intraocular pressure, arterial blood pressure (BP) and ocular perfusion pressure is poorly understood.

OBJECTIVES

This systematic review aims to provide clinicians with the latest literature regarding the management of arterial BP in glaucoma patients.

METHODS

A systematic search was performed in Medline, Embase, Web of Science and Cochrane Library. Articles written in English assessing the influence of arterial BP and systemic antihypertensive treatment of glaucoma and its management were eligible for inclusion. Additional studies were identified by revising references included in selected articles.

RESULTS

80 Articles were included in this systemic review. A bimodal relation between BP and glaucoma progression was found. Both high and low BP increase the risk of glaucoma. Glaucoma progression was, possibly via ocular perfusion pressure variation, strongly associated with nocturnal dipping and high variability in the BP over 24 h.

CONCLUSIONS

We concluded that systemic BP level associates with glaucomatous damage and provided recommendations for the management and study of arterial BP in glaucoma. Prospective clinical trials are needed to further support these recommendations.