Glaucoma is a leading cause of irreversible blindness worldwide, characterized by progressive optic nerve damage and visual field loss, often associated with elevated intraocular pressure (IOP). Although the primary focus of glaucoma research and management has been on the optic nerve and IOP, emerging evidence suggests that corneal changes, particularly in the corneal endothelium and central corneal thickness (CCT), may also play a role in the pathophysiology of glaucoma. It currently affects over 60 million people worldwide, a number projected to surpass 110 million by the year 2040¹. Primary glaucoma—which includes primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG)—poses a significant public health challenge due to its gradual onset and potential for unnoticed progression².In the holistic management of glaucoma, assessing both structural and functional aspects of the cornea is vital—particularly the health of the corneal endothelium and the measurement of central corneal thickness (CCT)³. The corneal endothelium consists of a monolayer of hexagonal cells located on the inner surface of the cornea. Its main function is to regulate corneal hydration through active fluid transport, which is essential for maintaining corneal transparency. Key indicators of endothelial function include endothelial cell density (ECD), cell hexagonality, and the coefficient of variation (CV) in cell size. In glaucoma patients, the endothelium may become compromised due to chronic elevation of IOP, repeated ocular procedures, or the long-term use of topical medications. Research has demonstrated that sustained high IOP can lead to a reduction in endothelial cell count and structural alterations, which may impair corneal clarity and affect vision⁴. CCT is another vital metric in the assessment of glaucoma. It represents the thickness of the central part of the cornea and is considered an independent risk factor for glaucoma development and progression. A thicker cornea may result in overestimated IOP readings, whereas a thinner cornea might lead to underestimations, potentially skewing the clinical evaluation and treatment strategy5. CCT is also thought to reflect the biomechanical strength of the cornea, influencing its ability to resist elevated IOP. Evidence suggests that individuals with thinner corneas have a higher risk of developing glaucoma and may experience a more rapid progression of the disease6. As such, incorporating CCT measurement into routine evaluations is important for accurate diagnosis, risk prediction, and treatment planning. Interest is increasing in exploring the link between corneal endothelial properties and CCT in glaucoma patients. Both elements are modulated by IOP and can also be influenced by systemic health conditions, age, and ethnicity. However, their precise relationship remains inconclusive. Some investigations have shown a positive correlation between CCT and ECD, proposing that thicker corneas may indicate healthier endothelium7. In contrast, other studies have found no statistically significant association, suggesting that the mechanisms influencing these two parameters may differ8. Gaining a deeper understanding of how corneal endothelial function and CCT interact in glaucoma could provide valuable insights into the disease process and help refine management approaches. This study aims at evaluating damage to corneal endothelium and central corneal thickness in patients of primary glaucoma. Additionally, the study sought to determine the effect of age on these parameters in glaucoma patients compared to age-matched healthy controls.

A hospital based cross-sectional observational study was conducted to evaluate and correlate central corneal thickness and corneal endothelial parameters in primary glaucoma patients. The study was carried out in the Department of Ophthalmology at Gandhi Medical College, Bhopal. The total duration of the study was 18 months, from May 2023 to October 2024. The study population included all primary glaucoma patients above 18 years of age patients attending Department of Ophthalmology, Gandhi Medical College, Bhopal. An equal number of age-matched healthy controls were also enrolled for comparative evaluation. Patients with secondary glaucoma, history of ocular trauma, previous ocular surgeries, or history of corneal diseases such as corneal endothelial dystrophy, corneal opacity etc. were excluded. Ethical clearance was obtained from the Institutional Ethics Committee of Gandhi Medical College, Bhopal. Participants were briefed about the study’s purpose and process. Written informed consent was taken prior to data collection, and all participants were assured of confidentiality and anonymity. Detailed history and comprehensive examination including best- corrected visual acuity, slit lamp biomicroscopy, Optic disc evaluation, gonioscopy, intra- ocular pressure by applanation tonometry of each patient were documented. Detailed specular microscopy was performed to examine corneal parameters including endothelial cell density, coefficient of variation (CV), of cell size, and percentage of hexagonal cells using a specular microscope (REXXAM SPM-700). Central Corneal Thickness (CCT) Measurement was done using an Ultrasonic Pachymeter (Sonomed 300AP+). Statistical Analysis Data collected were compiled and analyzed using IBM SPSS version 27.0. Descriptive statistics, including means, standard deviations, and simple proportions, were used to summarize the data. For inferential analysis, Chi-square tests and student t- test were performed. A p-value < 0.05 was considered statistically significant for all tests.

A total of 40 patients diagnosed with primary glaucoma and 40 age-matched healthy controls were included in the study. Participants were stratified into three age groups: 20–40 years, 41–60 years, and >60 years. The majority of participants fell within the 41–60year group (42.5%), followed by those over 60 years (37.5%)[Table1]. This age-matched stratification ensured valid comparisons across the age spectrum and minimized age as a confounding factor for corneal measurements. Central Corneal Thickness (CCT) Among glaucoma patients, the mean CCT declined from 521.48 µm (20–40 years) to 494.81 µm (>60 years). Controls showed a similar trend but maintained higher CCT values at each age group [Table2]. A statistically significant difference (p<0.001) was observed, suggesting that both age and glaucomatous pathology influenced corneal thinning. Corneal Endothelial Cell Density (ECD) In glaucoma cases, ECD decreased from 2302.18 cells/mm² in the youngest age group to 2150.20 cells/mm² in the oldest age group [Table3]. The difference was more pronounced in glaucomatous eyes and the results are significant (p=0.047), highlighting the deleterious effect of glaucoma on endothelial health, in addition to normal age-related attrition. Coefficient of Variation of Cell Size (CV) Coefficient of variation, an indicator of polymegathism, increased with age in both groups. However, glaucoma patients consistently had higher CV values across all age brackets, indicating more pronounced endothelial cell size variability[Table4]. The statistically significant difference (p=0.040) reinforced the concept that glaucomatous eyes exhibit greater endothelial stress and cellular remodeling. Percentage of Hexagonal Cells (6A) Hexagonality percentage declined with age, with glaucomatous eyes showing significantly lower values compared to controls in all age groups. The youngest glaucoma group had a hexagonality of 34.68%, compared to 40.68% in controls, with further declines observed with age[Table5]. The statistically significant reduction in hexagonality in cases (p<0.001) pointed to accelerated pleomorphism in glaucoma, reflecting compromised endothelial function. Central corneal thickness and Corneal Endothelial Cell Density When CCT was stratified into three ranges (>540 µm, 501–539 µm, <500 µm), a declining trend in endothelial cell density was noted with decreasing CCT, particularly in glaucoma patients [Table6]. While not statisticallysignificant (p=0.156), this pattern suggested that thinner corneas may be associated with lower endothelial cell counts, supporting the hypothesis of a shared pathological mechanism affecting both CCT and endothelial health in glaucoma. ECD showed a significant inverse relationship with IOP in both POAG and PACG. POAG eyes with IOP >30 mmHg had a markedly reduced ECD of 1839.38 cells/mm² [Table7]. A statistically significant p-value (<0.001) underscored the destructive impact of raised IOP on endothelial cells, especially in POAG, where intraocular pressure may exert cumulative stress on the endothelium. TABLE-1: Age Wise Distribution of Cases and Controls AGE GROUP CASES CONTROL TOTAL PERCENTAGE 20 – 40 Years 07 09 16 20 41 – 60 Years 18 16 34 42.5 More than 60 Years 15 15 30 37.5 Total 40 40 80 100 Table 2: Comparison of Central Corneal Thickness (CCT) According to Age AGE GROUP CENTRAL CORNEAL THICKNESS (CCT) in µm P VALUE CASES (MEAN ± SD) CONTROL (MEAN ± SD ) 20 – 40 Years 521.48 ± 30. 87 524.42 ± 23.17 <0.001 41- 60 Years 506.41 ± 27.11 521.77 ± 10.81 More than 60 years 494.81 ± 27.32 519.20 ± 32.60 Table 3: Comparison of Corneal Endothelial Cell Density (ECD) According to Age AGE GROUP CORNEAL ENDOTHELIAL CELL DENSITY (CD) in cells/ mm2 P VALUE CASES (MEAN ± SD) CONTROL (MEAN ± SD) 20 – 40 Years 2302.18 ± 106.08 2366.28 ± 174.13 0.047 41 – 60 Years 2210.76 ± 224.62 2292.16 ± 94.16 More than 60 Years 2150.20 ± 225.78 2246.46 ± 99.13 Table 4: Comparison of Coefficient of Variation (CV) According to Age AGE GROUP COEFFICIENT OF VARIATION (CV) in % P VALUE CASES (MEAN ± SD) CONTROL (MEAN ± SD) 20 – 40 Years 46.56 ± 3.98 37.42 ± 3.90 0.040 41 – 60 Years 47.26 ± 7.18 38.66 ± 4.224 More than 60 Years 49.58 ± 9.31 44.93 ± 8.75 Table 5: Comparison of Hexagonality (6A) According to Age AGE GROUP HEXAGONALITY (6A) in % P VALUE CASES (MEAN ± SD) CONTROL (MEAN ± SD) 20 – 40 Years 34.68 ± 4.29 40.68 ± 4.44 <0.001 41 – 60 Years 33.70 ± 5.97 38.70 ± 5.97 More than 60 Years 32.83 ± 3.60 36.83 ± 4.30 Table 6: Comparing Central Corneal Thickness (CCT) with Corneal Endothelial Cell Density (ECD) CENTRAL CORNEAL THICKNESS (CCT) CORNEAL ENDOTHELIAL CELL DENSITY (ECD) in cells/mm2 P value CASES (MEAN ± SD) CONTROL (MEAN ± SD) More than 540 µm 2262.50 ± 155.75 2379 ± 224.76 0.156 501 -539 µm 2149.59 ± 169.54 2342.5 ± 148.86 Less than 500 µm 2105.83 ± 279.46 2188 ± 312.12 Table 7: Relationship of Corneal Endothelial Cell Density (ECD) with Intraocular Pressure (IOP) INTRAOCULAR PRESSURE (IOP) CORNEAL ENDOTHELIAL CELL DENSITY (ECD) in cells/mm2 P VALUE POAG (MEAN ± SD) PACG (MEAN ± SD) < 20 mmHg 2303.19 ± 203.54 2308.50 ± 91.05 <0.001 21 – 30 mmHg 2079.55 ± 141.93 2243.17 ± 144.06 More than 30 mmHg 1839.38 ± 100.88 -

In the present study, the majority of glaucoma patients were within the 41–60 years age group, suggesting that glaucomatous changes primarily emerge during mid to late adulthood. This age distribution is consistent with previous findings by Sugumaran et al.9 (2022), who reported that most primary glaucoma cases occurred between 51 and 65 years, indicating a heightened vulnerability of the corneal endothelium in this age range. Similarly, Elagamy et al.10 (2022) observed a mean patient age of 51.43 ± 7.02 years, while Mossa et al. 11 (2022) reported a comparable mean age of approximately 58.5 years among individuals with primary glaucoma. These findings collectively underscore the role of aging not only in the onset of glaucoma but also in contributing to corneal biomechanical and endothelial alterations that may influence disease progression. The present study revealed a statistically significant decline in central corneal thickness (CCT) with advancing age (p < 0.001), aligning with findings from previous research. The mean CCT was 521.48 ± 30.87 μm in the 20–40 years age group, 506.41 ± 27.11 μm in the 40–60 years group, and 494.81 ± 27.32 μm in individuals over 60 years. The age-related decline in CCT observed in this study highlights the impact of aging on corneal structure, which may be exacerbated in glaucoma patients due to chronic IOP elevation and associated pathophysiological changes. Elagamy et al.10 (2022) similarly reported a weak negative correlation between age and CCT in patients with primary open-angle glaucoma (POAG), with mean CCT values of 529 μm in the 35–50 years age group and 522 μm in those aged 51–65 years. Taken together, these findings underscore the influence of age on corneal thickness, which is a key variable in accurately interpreting intraocular pressure and optimizing glaucoma management. The corneal endothelium is critical for maintaining corneal clarity and ocular health through its pump and barrier functions, and its status is reflected in cell density and morphology. Since endothelial cells have limited regenerative ability, maintaining their integrity is essential. A significant reduction in endothelial cell density (ECD) was observed in glaucomatous eyes compared to age-matched normal controls (p = 0.047), supporting the concept that glaucoma results in endothelial compromise. The mean ECD among glaucoma cases was 2302.18 ± 106.08 cells/mm² in the 20–40 years group, 2210.76 ± 224.62 cells/mm² in the 40–60 years group, and 2150.20 ± 225.78 cells/mm² in individuals over 60 years. These findings concur with Bhomaj et al.12 (2020), who reported significantly reduced endothelial cell counts in primary glaucoma patients than normal controls. Kang et al.13 (2022) also reported significantly reduced ECD in both POAG (2251 cells/mm²) and PACG (2287 cells/mm²) compared to controls (2611 cells/mm²). Similarly, Swamy and Tasneem14 (2020) demonstrated significantly lower endothelial cell density in glaucoma patients compared to healthy controls (p < 0.001). Yu et al.15 (2019) also observed reduced ECD in POAG (2757 cells/mm²) versus controls (2959 cells/mm²), attributing the loss to mechanical stress from raised IOP and potential medication toxicity. These data reinforce the heightened vulnerability of the corneal endothelium in primary glaucoma. Corneal endothelial cells are characteristically hexagonal and arranged in a uniform mosaic pattern, essential for maintaining corneal deturgescence and transparency. Therefore, both cell density and morphological integrity are critical indicators of corneal health. In this study, patients with primary glaucoma exhibited a significant decrease in the percentage of hexagonal cells along with a notable increase in the coefficient of variation (CV), reflecting pleomorphism and polymegathism. These morphological alterations suggest endothelial stress and dysfunction. Hexagonality serves as an indicator of endothelial cellular uniformity, with reduced percentages signifying pleomorphism and increased physiological stress on the endothelium. In the present study, glaucoma patients demonstrated significantly lower hexagonality compared to controls (p < 0.001), indicating compromised endothelial integrity. These findings are supported by Kang et al.13 (2022), who also reported a decline in hexagonality correlating with the severity of glaucoma, reinforcing its utility as a reliable marker of chronic endothelial stress and dysfunction in glaucomatous eyes. The study had few limitations. One limitation of this study is the relatively small sample size, which may restrict the generalizability of the findings to the broader population. Also, the study’s cross-sectional nature precludes evaluation of longitudinal changes in central corneal thickness and endothelial cell morphology over the course of disease progression or treatment.

This study provides evidence that patients with primary glaucoma exhibit significant changes in corneal endothelial parameters and central corneal thickness. These corneal parameters may function as additional indicators of disease progression and severity. The observed endothelial cell loss and morphological abnormalities suggest compromised corneal health in glaucoma patients, underscoring the importance of thorough anterior segment evaluation. Incorporating CCT and endothelial assessments into routine glaucoma management could enhance diagnostic accuracy and guide treatment decisions more effectively. Further longitudinal studies are needed to explore the temporal changes in corneal parameters and their correlation with disease progression in glaucoma

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