European Journal of Cardiovascular Medicine

Central corneal thickness (CCT) is a vital metric in ophthalmology, affecting intraocular pressure (IOP) readings, corneal biomechanics, and the evaluation of risks associated with eye disorders like glaucoma and keratoconus. Variability in CCT is linked to various demographic and physiological parameters, such as age, gender, refractive errors, and axial length [1-5]. Comprehending these relationships is crucial for enhancing diagnostic precision and refining care options for refractive and ocular disorders [3-5].

This prospective observational study examines the correlation between CCT and these factors in patients. Numerous research [4-8] have documented age-related corneal thinning, however, the discourse surrounding gender disparities in corneal thickness remains contentious, with several studies indicating that males typically possess thicker corneas than females. Moreover, refractive errors, especially myopia and hyperopia, are thought to affect CCT owing to variations in corneal curvature and structural adaptation. Axial length, a crucial factor in the refractive state, also significantly influences corneal shape. This study aims to offer significant insights into the normative

CCT distribution across various demographic groups by analyzing these connections. The results may enhance clinical guidelines for refractive surgery, glaucoma risk assessment, and individualized ocular care, especially among patient demographics. Hence the present study aimed to determine CCT to age, gender, refractive errors, and axial length among patients visiting tertiary care center in South India.

A cross-sectional study was performed at Sri Venkateshwara Medical College Hospital and Research Centre, a tertiary care facility in Puducherry. The study sought to assess the correlation between CCT and several variables, including age, gender, refractive errors, and axial length, in patients visiting the ophthalmology outpatient department.

The study encompassed participants aged 20 to 70 years both the gender who received standard ophthalmologic evaluations. Participants were recruited sequentially according to established inclusion and exclusion criteria.

Inclusion Criteria: Patients devoid of a history of ocular surgery or trauma. No signs of corneal illness or dystrophy, readiness to participate, and furnish informed consent.

Exclusion Criteria: Previous ocular surgery, trauma, or corneal pathology; the presence of glaucoma, keratoconus, or systemic diseases influencing corneal thickness (e.g., diabetes, connective tissue disorders); and contact lens usage within the preceding period before measurement.

Calculation of Sample Size: The cross-sectional study method was used to figure out the sample size. In this method, Z stands for the standard normal variate (1.96 for 95% confidence), p for the expected prevalence of corneal thickness change, and d for the margin of error. According to previous research, a sample size of 100 eyes (55 patients) was deemed adequate for statistical analysis.

The Institutional Ethics Committee provided ethical approval for the study. Informed consent was obtained in writing from all individuals before registration. The research complied with the principles of the Declaration of Helsinki.

Data Acquisition: Every subject received an extensive ophthalmologic evaluation, comprising a focus on sight. We conducted an acuity assessment on a Snellen chart. We conducted the refraction assessment using both objective and subjective methods, utilizing an autorefractometer and retinoscopy. We obtained the axial length measurement using A-scan ultrasonography and ultrasonic biometry. We measured the central corneal thickness using an ultrasonic pachymeter. A slit-lamp examination was performed to exclude any ocular disease. Data were examined with the help of SPSS. For continuous data, descriptive statistics were computed, including mean and standard deviation. 

Table 1 shows the CCT in relation to age. The mean CCT in the age group of 20-30 is 562.14 ± 32.4 microns, and the range is 468 to 595 microns. In the age group of 31-40 the mean CCT is 554.34 ± 21.56 microns, the range is 512.22 to 594.19. In the age group of 41-50, the mean CCT is 546.88 ± 21.56 microns, and the range is 481 to 592 microns. In the age group of 51-60, the mean CCT is 537.12 ± 34.89 and the range is 498 to 576 microns. In the age group of 61 -70, the mean CCT is 530.56 ± 34.87 microns, and the range is 479 to 592 microns.  [Table 1].

Table 1: Central corneal thickness (CCT) with age

Figure 1 shows the CCT in relation to gender. The mean CCT in males is 540.64 ± 23.7.2 microns, and range is 446.17 to 599.36 microns. In females, the mean CCT is 547.76 ± 34.21 microns, and the range is 511.3 to 612.56 [Figure 1].

Figure 1: Central corneal thickness (CCT) with regard to gender

Table 2 shows the CCT with relation to central corneal thickness. The mean CCT in low myopia is 542 ± 25 microns, and the range is 498 to 560 microns. In moderate myopia, the mean CCT is 538 ± 26 microns, and the range is 500.09 to 624.29. In high myopia, the mean CCT is 529 ± 23.7 microns, and the range is 521 to 540  microns. In hypermetropia, the mean CCT is 538.17 ± 27.6 and the range is 521 to 546 microns.  [Table 2].

Table 2: Central corneal thickness (CCT) with regards to refractive errors

The current study compares central corneal thickness (CCT) across age groups, indicating a steady drop in CCT with increasing age. The mean CCT in the youngest age group (20-30 years) was 562.14 ± 32.4 µm, progressively falling to 530.56 ± 34.87 µm in those aged 61-70 years. This trend is consistent with prior research, supporting the hypothesis of an age-related reduction in CCT. Globally, comparable findings have been observed. Wong et al. [9] observed that CCT decreased significantly with age in a Chinese sample, with younger people having higher mean CCT values than older adults. In a study in Barbados, Nemesure et al. [10] found that the cornea becomes thinner as people get older. They linked this change to the loss of cells and less moisture in the cornea. Sharma et al. [11] found that CCT decreases with age in an Indian population, with values ranging from 558 ± 29 µm in young adults to 532 ± 35 µm in the elderly. This implies regional stability in CCT trends among the Indian demographic, including the Central Indian group studied in this study.

From a physiological standpoint, the drop in CCT with age may be related to changes in corneal endothelial cell density and function. Gokhale et al. [12] found that age-related endothelial cell loss reduces stromal hydration, which contributes to corneal thinning. Doughty and Zaman [13] have postulated that long-term oxidative stress and metabolic alterations in the corneal epithelium could contribute to this age-related decline. The clinical significance of these discoveries is critical, especially in terms of intraocular pressure (IOP) measures. Thinner corneas can result in underestimating IOP, which is important in glaucoma risk assessment. The Ocular Hypertension Treatment Study [14] conducted a landmark study that demonstrated the need to take CCT into account when diagnosing and treating ocular hypertension and glaucoma. Our findings underscore the importance of age-adjusted CCT considerations in clinical practice. Also, the differences in CCT values among different age groups in our study indicate that there are individual differences. These differences might be affected by genes, the environment, and lifestyle choices. Research in Western populations [13,15] found that the central corneal thickness (CCT) is usually higher than in Asian groups. This suggests that there may be differences in corneal structure based on ethnicity.

The study found that females have a slightly larger mean central corneal thickness (CCT) (547.76 ± 34.21 µm) than males (540.64 ± 23.72 µm). This observation is consistent with some global research conducted that differs from others, demonstrating that findings vary across populations. For example, Kang et al. [16] found that male participants had a thicker central corneal epithelium than females, indicating a gender-related differential in corneal thickness favoring males. Similarly, a study of a Russian population [17] discovered that CCT was greater in men than in women, lending credence to the idea that males have thicker corneas. In contrast, several studies have revealed no significant gender variations in CCT. Sanchis-Gimeno et al. [18] found no significant differences in mean central and paracentral corneal thickness values between men and women. Furthermore, a research study of Latino populations [19] found modest but statistically significant differences, with men having slightly bigger corneas than women; however, these variations were deemed non-clinically relevant. Changes in study populations, measuring methodologies, and sample sizes may contribute to the heterogeneity in these findings. Factors such as ethnicity, age distribution, and environmental effects may all contribute to the disparities reported in research. Furthermore, hormonal fluctuations, particularly in females, may affect corneal thickness. A study [20] on the effects of sex, oral contraception, and menstrual cycle phase discovered that cycling women had considerably higher corneal thickness than oral contraceptive users, indicating hormonal modulation of corneal characteristics. Understanding gender differences in CCT is crucial in clinical settings, particularly for measuring IOP and assessing glaucoma risk. Thinner corneas might cause an underestimation of IOP, potentially delaying glaucoma diagnosis and treatment. As a result, taking into account gender-specific CCT variations can improve IOP assessment accuracy and patient outcomes.

The examination of CCT for different refractive errors reveals significant differences. The average CCT for low myopia is 542 ± 26 microns, with a range of 498 to 560 microns. Moderate myopia had a higher mean CCT of 538 ± 26 microns, ranging from 502 to 558 microns. High myopia has an average CCT of 529 ± 25 microns, ranging from 512 to 540 microns. These findings are consistent with global investigations undertaken between 2015 and 2025. A study of the eastern Egyptian population [21] showed that myopic people had an average CCT of 532.8 microns, plus or minus 32.6 microns. Hyperopic adults had an average CCT of 530.8 microns, plus or minus 37.2 microns. A research study on the adult Egyptian population [22] reported a mean CCT of 539.23 ± 32.24 microns among myopic patients. The observed rise in mean CCT from low to high myopia shows a possible link between increasing levels of myopia and increased corneal thickness. This tendency is similar to results from other regions. For instance, a study in the adult Egyptian population [21] found a slight positive connection between myopic refractive error and corneal power, indicating that higher myopia is associated with steeper corneas. Hypermetropia has a somewhat lower mean CCT (517.19 ± 27.61 microns compared to myopic groups. This observation is consistent with the Eastern Egyptian study, which found a mean CCT of 530.8 ± 37.2 microns in hyperopic participants [21]. The mean CCT for astigmatism is 532.72 ± 24.11 microns, which falls within the range recorded for myopic and hyperopic persons. This finding is consistent with previous studies on the link between corneal thickness and astigmatism. A study [22] that examined the relationship between myopic refractive error, corneal power, and CCT discovered that keratometric astigmatism had a high positive connection with refractive astigmatism. It's important to note that while these trends are observed, individual variations exist, and factors such as age, sex, and ethnicity can influence CCT. Therefore, personalized assessments are essential in clinical practice.

The average eye length was found to be 23.47± 0.80  mm in males and 23.20± 0.57 mm in females. This matches global studies from 2015 to 2025, which show that males generally have longer eye lengths than females. A research study in Cameroon [23] indicated that men had a mean axial length of 24.01 ± 0.88 mm, while women had a mean of 23.47 ± 0.84 mm. The difference was statistically significant. A review of major population-based research found that male eyes had a mean axial length of 23.93 mm, whereas female eyes had 23.51 mm [24]. These disparities are frequently linked to variances in general body size and ocular anatomy across genders. Ethnicity also influences axial length disparities. In a meta-analysis of Asian and European populations, male participants had somewhat greater axial lengths than females across all age categories. Notably, Asian children showed higher increases in axial length with age than their European counterparts, indicating that ethnicity affects ocular development rates [25]. Age-related changes exacerbate the link between axial length and refractive errors. A study of ocular biometry in Bosnia and Herzegovina [26] found that females have shorter axial lengths, steeper corneas, and shallower anterior chambers than males. These differences were stable across age groups, implying that gender-related ocular structural variations exist throughout life. The differences in mean axial lengths between genders and populations highlight the need to take demographics into account when doing ophthalmic evaluations. Understanding these distinctions is critical for proper diagnosis and treatment of refractive errors and other eye disorders.

The study concludes that CCT varies significantly by age, gender, refractive errors, and axial length. Age is associated with corneal thinning, while gender differences suggest physical and hormonal factors. There was no significant difference in CCT among myopia, hypermetropia, and emmetropia. There was no significant relationship between CCT and axial length. Understanding regional differences can improve eye care and intraocular pressure measurements. Longitudinal studies with larger sample sizes and partnerships between multiple centers are needed to confirm these results and look into how genes and the environment affect corneal shape.

Conflict of interest

There is no conflict of interest among the present study authors

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