Back to Journals » Clinical Ophthalmology » Volume 18
Impact of Environmental Factors on Glaucoma Progression: A Systematic Review
Authors Almarzouki N
Received 26 July 2024
Accepted for publication 25 September 2024
Published 30 September 2024 Volume 2024:18 Pages 2705—2720
DOI https://doi.org/10.2147/OPTH.S484855
Checked for plagiarism Yes
Review by Single anonymous peer review
Peer reviewer comments 2
Editor who approved publication: Dr Scott Fraser
Nawaf Almarzouki
Department of Ophthalmology, King Abdulaziz University Hospital, Jeddah, Saudi Arabia
Correspondence: Nawaf Almarzouki, Department of Ophthalmology, King Abdulaziz University Hospital, Jeddah, Saudi Arabia, Email [email protected]
Background: Glaucoma, a leading cause of irreversible vision loss, is characterized by progressive degeneration of retinal ganglion cells. Intraocular pressure (IOP) remains a well-established risk factor, but recent research suggests environmental and lifestyle factors may also play a role.
Objective: This review aimed to evaluate the current evidence on the impact of environmental factors on glaucoma progression.
Methods: We conducted a systematic review following PRISMA guidelines, searching various databases for studies on environmental factors and glaucoma progression.
Results: Our review identified several key findings. IOP remains the most crucial modifiable risk factor. Aerobic exercise and mindfulness practices may lower IOP and provide neuroprotection. Lifestyle modifications like smoking cessation and balanced diets were also emphasized. Studies suggest air pollution exposure, particularly PM2.5, may be associated with an increased risk of glaucoma. However, the studies were primarily observational, and more research is needed to establish causality and elucidate underlying mechanisms.
Conclusion: This review highlights the multifaceted nature of glaucoma, emphasizing the interplay between established risk factors (IOP) and emerging environmental influences (air pollution). Environmental factors hold promise as potential targets for glaucoma prevention and management strategies. Future research should focus on well-designed studies to investigate causal relationships and biological mechanisms.
Keywords: glaucoma, intraocular pressure, IOP, environmental factors, air pollution, lifestyle modifications, aerobic exercise, diet, public health
Introduction
Glaucoma is a leading cause of irreversible blindness globally.1 It is characterized by damage to the optic nerve and loss of visual field and is often associated with elevated intraocular pressure (IOP). Despite advancements in diagnostic and therapeutic approaches, understanding the multifactorial pathogenesis of glaucoma, involving genetic predisposition, ocular factors, and environmental influences, remains crucial.2,3 Increasingly, research has emphasized the impact of environmental factors on glaucoma progression, alongside genetic susceptibility and ocular parameters.
Environmental factors such as lifestyle choices, occupational exposures, geographical variations, socioeconomic disparities, and climatic conditions are pivotal in influencing the risk of developing glaucoma and its severity and progression.4–6 Factors, including smoking, alcohol consumption, diet, physical activity levels, and exposure to air pollution, have been associated with the onset and progression of glaucoma through mechanisms such as oxidative stress, inflammation, and neurodegeneration.
The significance of environmental factors as modifiable risk factors highlights the importance of preventive interventions and personalized treatment strategies. Performing a systematic literature review on the impact of environmental factors on glaucoma progression is essential for synthesizing current evidence, identifying research gaps, and elucidating underlying mechanisms. By comprehensively analysing available data, this study aims to provide insights into the complex interplay between environmental exposures and glaucoma pathogenesis, thereby enhancing clinical management and patient outcomes.
In summary, investigating the influence of environmental factors on glaucoma progression is crucial for advancing our understanding of the disease and optimizing therapeutic approaches. Integrating genetic, ocular, and environmental factors in a comprehensive framework can improve risk assessment, facilitate early detection, and enable targeted interventions for individuals at risk of glaucoma-related vision loss. This systematic review provides valuable insights to advance glaucoma research and guide future investigations into the environmental determinants of disease progression.
Aims & Objectives
To conduct a systematic review of published studies investigating the association between environmental factors and glaucoma progression, focusing on both epidemiological and mechanistic research by evaluating the methodological quality of the included studies, including study design, sample size, data collection methods, and statistical analyses, to ensure the validity and reliability of the findings.
Methodology
Search Strategy
Figure 1 depicts the PRISMA flowchart, a standardized reporting guideline to improve the transparency and reproducibility of systematic reviews and meta-analyses.7 This flowchart outlines the study selection process, from the initial search to the final included studies. A comprehensive and systematic search was conducted to identify studies evaluating the impact of environmental factors on glaucoma progression. The following databases were searched: PubMed, MEDLINE, Embase, Cochrane Library, CINAHL, and relevant grey literature sources. The search was limited to articles published in English from January 2000 to May 2024. Keywords and Medical Subject Headings (MeSH) terms included “glaucoma”, “environmental factors”, “progression”, “air pollution”, “temperature”, “humidity”, “light exposure”, and “socioeconomic factors”.
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Figure 1 The PRISMA flowchart. Notes: Adapted from Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 2021; 372: n717. |
Inclusion and Exclusion Criteria
Inclusion Criteria
Studies that investigated the relationship between environmental factors and glaucoma progression,
Peer-reviewed articles, including observational studies (cohort, case-control, and cross-sectional) and clinical trials,
Studies with clearly defined diagnostic criteria for glaucoma, and studies that provided quantitative measures of glaucoma progression (eg, changes in intraocular pressure, visual field loss, or optic nerve damage).
Exclusion Criteria
Articles that did not focus on environmental factors,
Studies without clear definitions of glaucoma progression,
Editorials, and case reports, and all non-English publications.
Data Extraction
Data were extracted independently by two reviewers using a standardized data extraction form. The following information was collected:
Study characteristics: author, year of publication, country, study design.
Participant characteristics: sample size, age, gender, glaucoma type.
Environmental factors: type of exposure (eg, air pollution, temperature), duration and intensity of exposure.
Outcomes: measures of glaucoma progression (eg, intraocular pressure, visual field analysis, optic nerve assessment).
Results: main findings related to the impact of environmental factors on glaucoma progression.
Discrepancies between reviewers were resolved through discussion, and if necessary, a third reviewer was consulted.
Quality Assessment
The assessment focused on:
Selection bias: representativeness of the exposed cohort, selection of the non-exposed cohort, ascertainment of exposure, and demonstration that outcome of interest was not present at the start of the study.
Comparability: control for confounding factors.
Outcome assessment: method of outcome assessment, follow-up duration, and adequacy of follow-up.
Ethical Considerations
As this study involved a review of published data, no ethical approval was required. However, the review adhered to ethical standards for systematic reviews, including transparency, rigor, and reproducibility.
Results
Table 1 presents eleven studies on glaucoma management and risk factors. Rivera et al8 highlight risk factors for primary open-angle glaucoma progression and call for further research. Kumar et al.9 In their study focused on intraocular pressure reduction through pharmacological and surgical therapies and lifestyle factors like aerobic exercise, mindfulness, caffeine, and nicotinamide supplementation. Leske et al10 emphasize treatment and IOP reduction in mitigating glaucoma progression. Perez et al11 emphasize the importance of lifestyle, exercise, and nutrition in preventing or slowing glaucoma progression. Hecht et al12 discussed the benefits of moderate aerobic exercise and a high-fiber diet in managing primary open-angle glaucoma. Blumberg et al13 identified elevated IOP as the most critical risk factor for glaucoma. Gillmann14 and team delves into the immediate effects of everyday activities, such as emotional stress and resistance training exercises, on intraocular pressure profiles in patients diagnosed with open-angle glaucoma and individuals suspected of having the condition. The study evaluates how these common activities might influence IOP levels. Meanwhile, Dziedziak et al15 provided a review of the existing evidence on the potential benefits of dietary antioxidants in preventing and treating two age-related neurodegenerative ophthalmic diseases: age-related macular degeneration and glaucoma. The authors discuss the possible role of antioxidants in mitigating these conditions. Interestingly, Yang et al16 in their large-scale, population-based study conducted in China investigated the association between long-term exposure to ambient fine particulate matter (PM2.5) and the risk of developing glaucoma. The findings revealed a link between PM2.5 exposure and an increased likelihood of glaucoma, particularly primary angle-closure glaucoma. The study also identified middle-aged adults and non-smokers as being more susceptible to the detrimental effects of PM2.5 on glaucoma risk. Adi et al17 provided a review of the current evidence on the role of diet in influencing various aspects of glaucoma, encompassing obesity, dietary components, and the use of supplements. The authors discuss how these dietary factors might influence IOP, the incidence of glaucoma, and the progression of the disease. Tribble et al18 highlighted glaucoma as a leading cause of vision loss due to progressive dysfunction and death of retinal ganglion cells. The authors propose that metabolic deficiencies and defects might play a significant role in the pathophysiology of glaucoma. The study suggests that modifying diet and exercise habits could be implemented by patients as an adjunct to traditional IOP-lowering therapies. These lifestyle changes might offer potential benefits for protecting retinal ganglion cells in glaucoma.
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Table 1 Summary of Included Studies |
Table 2 summarizes research on primary open-angle glaucoma, highlighting the importance of intraocular pressure (IOP) as a modifiable risk factor for glaucoma progression. Lifestyle modifications like aerobic exercise, mindfulness, and nicotinamide supplementation can slow disease progression. Treatment significantly reduces glaucoma progression risk, with initial IOP reduction crucial. Lifestyle changes like smoking cessation and a balanced diet may protect against glaucoma. Interventions like head elevation during sleep and moderate exercise can improve glaucoma progression. Risk factors include older age, lower ocular perfusion pressure, and central corneal thickness.
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Table 2 Main Findings and Study Objectives |
Table 3 presents a summary of studies on primary open-angle glaucoma (POAG), focusing on various methodologies and interventions. Key factors identified include intraocular pressure fluctuations and central corneal thickness (CCT). Lifestyle factors like aerobic exercise and mindfulness may lower IOP and provide neuroprotection. Treatments like argon laser trabeculoplasty reduced POAG progression risk. Lifestyle modifications like smoking cessation and balanced diets were also emphasized. Randomized controlled trials on food supplements and lifestyle changes also examined their effects on IOP. The studies emphasize the importance of managing IOP and identifying risk factors for POAG progression.
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Table 3 Study Design, Methodology, Interventions, and Outcomes |
Table 4 presents limitations and future research directions for glaucoma studies. Rivera et al8 suggest long-term studies to understand risk factors for disease progression and blindness, while Anika et al9 in their study highlighted inconsistencies in evidence on lifestyle factors. Leske et al19 in their study emphasized the variability in intraocular pressure measurements and the need for more data to distinguish risk groups. Perez et al11 suggested large-scale prospective or randomized controlled trials to confirm lifestyle habits and dietary components’ impact on glaucoma. Hecht et al7 emphasize the retrospective nature of current research and the importance of investigating cerebrospinal fluid pressure in different glaucoma subtypes.
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Table 4 Limitations and Future Research Directions |
Discussion
Glaucoma is a leading cause of irreversible vision loss worldwide. It is characterized by the progressive degeneration of retinal ganglion cells (RGCs) and their axons, ultimately resulting in visual field loss. While intraocular pressure (IOP) remains a well-established risk factor for glaucoma progression, recent research indicates that environmental and lifestyle factors may also significantly influence disease development and progression. The aim of this systematic review was to assess the current body of evidence regarding the impact of environmental factors on glaucoma progression.
Our review identified several key findings that support and expand upon existing research. First, we confirm that IOP is the most critical modifiable risk factor for glaucoma progression. This conclusion is consistent across multiple studies, including the Early Manifest Glaucoma Trial (EMGT),19 which demonstrated that effective treatment significantly reduces progression risk by half (The EMGT Group, 2000). Additionally, our analysis underscores the potential benefits of lifestyle modifications in lowering IOP and potentially slowing disease progression. Previous research has linked aerobic exercise to reduced IOP and slower rates of visual field deterioration in glaucoma patients.20 Furthermore, our review explores the potential neuroprotective effects of mindfulness practices, suggesting a promising area for future investigation into non-traditional glaucoma management interventions. While using nicotinamide supplements in glaucoma warrants further study, our findings align with preclinical research suggesting their potential neuroprotective properties.21
Our review also highlights the emerging connection between environmental pollution and glaucoma. The positive correlation we observed between long-term exposure to PM2.5, a significant component of air pollution, and glaucoma risk aligns with recent findings by Chiang et al.22 Their study similarly linked PM2.5 exposure to an increased risk of primary open-angle glaucoma (POAG) in a large Chinese population. Further research is essential to elucidate the mechanisms through which air pollution contributes to glaucoma development. Potential mechanisms include oxidative stress induced by air pollutants, leading to damage of RGCs, or inflammatory responses triggered by airborne particles.23 Investigating these pathways can provide valuable insights into the causal relationship between environmental pollution and glaucoma.
Our findings also underscore the susceptibility of specific populations to environmental risk factors. For instance, our review suggests that middle-aged adults and non-smokers may be more vulnerable to the effects of PM2.5 exposure on glaucoma risk. This susceptibility could be linked to age-related variations in blood–brain barrier function or individual differences in detoxification pathways that affect susceptibility to environmental toxins.24 Additionally, our review highlights the potential protective role of a balanced diet rich in specific nutrients against glaucoma. This aligns with previous research indicating the benefits of dietary antioxidants such as lutein and zeaxanthin in reducing oxidative stress and protecting retinal cells.25
Limitations of our review include the predominantly observational nature of the included studies, which complicates establishing definitive cause-and-effect relationships between environmental factors and glaucoma progression. Moreover, the variability in methodologies and interventions across studies limits our ability to draw definitive conclusions. Future research should prioritize well-designed prospective studies to investigate the causal relationships between environmental exposures and glaucoma. Additionally, future studies need to explore the biological mechanisms through which environmental factors contribute to glaucoma development. Furthermore, randomized controlled trials are essential to assess the effectiveness of specific lifestyle modifications, dietary interventions, or environmental mitigation strategies in preventing or slowing glaucoma progression.
Challenges and Ethical Considerations
While our review suggests promise for environmental modifications as potential glaucoma management strategies, implementing these changes can be challenging. For instance, air quality control measures often require significant infrastructure investments and policy changes, posing limitations in areas with limited resources. Additionally, individual efforts to reduce exposure to air pollution may be limited by factors such as dependence on private transportation or living in areas with high levels of industrial activity.
Ethical considerations also arise when discussing environmental interventions. Widespread pollution control strategies often require substantial financial resources. Striking a balance between environmental protection, economic development, and public health is crucial. Furthermore, the cost-effectiveness of implementing such strategies on a large scale needs to be carefully evaluated.
Conclusion
Our systematic review underscores the multifaceted nature of glaucoma, highlighting the interplay between established risk factors like intraocular pressure (IOP) and emerging environmental influences like air pollution. While the existing literature on environmental factors and glaucoma progression is rapidly evolving, our review offers several valuable contributions. Based on our findings, we recommend that clinicians consider incorporating environmental risk reduction strategies, such as reducing exposure to air pollution and promoting healthy lifestyle behaviors, into their glaucoma management plans. Future research should focus on elucidating the biological mechanisms through which environmental factors contribute to glaucoma development and progression, as well as evaluating the effectiveness of targeted interventions to address these factors.
Abbreviations
IOP, Intraocular Pressure; POAG, Primary Open-Angle Glaucoma; AMD, Age-Related Macular Degeneration; PM2.5, Fine Particulate Matter (with diameter 2.5 micrometres or less); RCT, Randomized Controlled Trial; MLS, Modifiable Lifestyle Interventions; CSF, Cerebrospinal Fluid; RGCs, Retinal Ganglion Cells; PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses.
Data Sharing Statement
All relevant data are within the paper.
Author Contributions
Author is responsible for conception and design, acquisition of data, or analysis and interpretation of data; drafting the article or revising it critically for important intellectual content; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.
Disclosure
The author declares that they have no conflicts of interest in this work.
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