Literature selection

After the initial screening process, 350 articles were extracted from nine databases (PubMed, PubMed Central, Scopus, Cochrane Library, Google Scholar, MEDLINE, EMBASE, LILACS, and Web of Science). After eliminating duplicates, non-English articles, and articles lacking full text, 163 articles were considered eligible. Fifty-six articles that did not align with the focus of the study and required more information on the imaging assessment used (n = 41) or had incomplete data (n = 15) were excluded. Fifteen studies were included in this review. These studies were published between 2012 and 2024. The PRISMA chart delineating the comprehensive process of literature collection and screening is shown in Fig. 1. Among these, retrospective studies emerged as the most prevalent study type, constituting six out of 15 studies. Among the remaining nine studies, four were cross-sectional, three were prospective, and two were observational.

Fig. 1

PRISMA flow diagram of the systematic screening process

Study characteristicsPatient demographics

These 15 studies included 3078 patients, and the number of females (n = 1557) was slightly greater than the number of males (n = 1521), excluding one study [13] that did not disclose the sex distribution. The patients included in the studies were between 20 and 84 years old, with the majority being over 50 years of age. All patients had highly myopic eyes, with an axial length of 26.0 mm or greater and a refractive error of less than − 6 diopters.

Imaging technology used

Twelve of the 14 studies used different OCT assessments, including enhanced depth imaging OCT (EDI-OCT), optical nerve head OCT, OCT angiography, stratus OCT, and swept-source OCT. However, one study [14] used color fundus images. When using OCT for assessing glaucoma in highly myopic eyes, interpreting the results is challenging because of the greater likelihood of false-positive diagnoses. Myopic eyes often show structural changes such as pRNFL thinning, which can be mistaken for glaucomatous damage. This becomes more difficult when standard normative databases not considering myopic eyes are used. Including a myopic normative database has been found to improve diagnostic specificity and reduce false positives without compromising sensitivity [15]. This is crucial for accurate diagnosis and management, especially in populations with a high prevalence of myopia.

Risk factors, structural findings, and functional findingsOutcomes of the study

Among the included studies, four discussed different diagnostic assessment tools [4, 5, 14, 16], four discussed glaucomatous damage [17,18,19,20], six reported the use of OCT assessments [5, 8, 21,22,23,24], three discussed associations with myopia [2, 4, 5], and three reported visual field progressions and microstructure, such as the distribution of lamina cribrosa defects (LCDs) in the optic disc and the proportion of abnormal clusters. Segmentation errors in OCT scans have been reported [2, 8, 10], and only one study reported artifacts and error analysis [11]. No studies have reported any potential complications.

Risk of bias assessment

Table 1 presents the quality of the included RCTs and non-RCTs based on the Jadad scale scores.

Table 1 Quality of the included studies according to the Jadad scale scores

All data from the articles were carefully reviewed for potential bias. Each of the fifteen studies underwent a risk of bias analysis, which revealed a low risk of bias. However, studies three and five showed a moderate risk of bias in domain 3 (D3) due to missing information about the intended classification of the intervention and a low to moderate risk of bias in domain 5 (D5) owing to missing data. The overall bias data are presented in a risk of bias plot, which shows that all included studies had low to moderate risk of bias, depicted in green and yellow, respectively. However, the overall bias was considered to be low. Figures 2 and 3 outline the variables included in the risk-of-bias assessment plot and summary.

Fig. 2

Graphical representation of the risk of bias analysis of individual studies. A low risk of bias was shown in 13 studies, and a moderate risk of bias was demonstrated in two studies

Fig. 3

Schematic representation of the summary of the risk of bias analysis. Plot showing an overall low risk of bias

Meta-analysis

Only six studies were included in the meta-analysis, which focused on success rates and imaging assessments. Eight studies were excluded because they did not report success or complication rates. The analysis included 3040 patients from studies reporting success and failure rates. Figure 4 shows a forest plot representing the success rates of the imaging assessments. In this meta-analysis of six studies involving 3,040 patients, we investigated the correlation between myopia and glaucoma, emphasizing structural and functional implications such as the formation of abnormal clusters, tissue microstructures, and aqueous outflow, in addition to risk factors and assessment modalities, mainly OCT, in high-myopia populations (OR = 12.0, 95% CI 10.1–4.7, P < 0.00001). These findings are consistent with those of the sensitivity analysis. The forest plot visually represents the odds ratios and corresponding CIs across the included studies. Each horizontal line, or “branch,” represents individual research, with the point estimate (dot) indicating the odds ratio. The horizontal line through the square conveys the CI, and the dot size reflects the weight of each study in the meta-analysis.

Fig. 4

A forest plot representing the success rates of the imaging assessments revealed the relationship between myopia and glaucoma, focusing on structural and functional implications. The forest plot represents the odds ratios and corresponding CIs. Each horizontal line represents individual research, and the point estimate (dot) indicates the odds ratio

In Study 1, conducted by Ehongo et al. [2], the observed odds ratio of 0.274, along with a narrow confidence interval, strongly suggested a protective effect against the development of glaucoma in individuals with myopia. This finding implies that people with myopia may have a lower likelihood of experiencing glaucomatous changes than those without myopia. In Study 7 by Zemborain et al. [24], the reported odds ratio of 1.703 indicated a moderate increase in the likelihood of glaucoma among myopic patients. Although the effect was not as pronounced as in other studies, it still signifies a notable increase in the risk of myopia-associated glaucoma.

In Study 10 by Lim et al. [14], a substantial odds ratio of 20.792 was reported, highlighting a strong and statistically significant association between myopia and the occurrence of glaucoma. This high odds ratio suggests a significantly heightened risk of glaucomatous changes in individuals with myopia, emphasizing the importance of considering myopia as a potential risk factor. Studies 12 and 11, which were conducted by Hung et al. and Nakano et al. [7, 22] further contributed to the evidence by demonstrating odds ratios of 17.100 and 17.000, respectively. These findings reinforce a significant link between myopia and glaucomatous changes, such as elongation and thinning of the lamina cribrosa, resulting in intralaminar changes and steepening of the translaminar cribrosa pressure gradient. The consistent odds ratios in these studies underscore the robustness of the observed association, strengthening the argument that myopia is a noteworthy factor in the context of glaucoma risk.

Finally, Study 15, conducted by Awadalla et al. [11], significantly strengthens the existing evidence by revealing an odds ratio of 15.540. These findings add further weight to the body of knowledge, indicating a significant link between myopia and the development of glaucoma. The consistent odds ratios reported in these studies collectively enhance our understanding of the association and underscore the importance of considering myopia as a potential risk factor for glaucomatous changes.

The results collectively underscore the consistency and robustness of the observed associations, as depicted in the forest plot. The dispersion of individual study results visually demonstrates the heterogeneity across the study estimates around the overall summary estimate. The forest plot is a powerful tool for revealing the nuanced findings of a meta-analysis, facilitating the interpretation of the collective evidence concerning myopia and its relationship with glaucoma.

The quantitative outcomes of the meta-analysis (OR = 12.0, 95% CI 10.1–4.7, P < 0.00001) revealed a substantial and statistically significant association between high myopia and glaucoma risk, further bolstering the hypothesis that high myopia is a notable risk factor for the development of glaucomatous changes. These comprehensive meta-analyses deepen our understanding of the association between high myopia and glaucoma and provide valuable insights into the scientific literature. Supplementary Tables 2 and 3 present the structural findings, such as refractive error, axial length, visual acuity, visual field index, and IOP, along with all corresponding extraction data.