|Year : 2018 | Volume
| Issue : 1 | Page : 6-11
The central corneal thickness and anterior chamber depth of adults in a Nigerian population
Eghosasere Iyamu, Juno Ohiremere Okukpon, Ibaruata Uduoise
Department of Optometry, Faculty of Life Sciences, University of Benin, Benin City, Edo State, Nigeria
|Date of Submission||11-Apr-2018|
|Date of Acceptance||09-Apr-2020|
|Date of Web Publication||11-Jul-2020|
Dr. Juno Ohiremere Okukpon
Department of Optometry, Faculty of Life Sciences, University of Benin, Benin City, Edo State
Introduction: The central corneal thickness (CCT) and anterior chamber depth (ACD) are important ocular parameters used in the assessment of risk factors relating to ocular morbidities. Determining the relationship between these parameters is fundamental to understanding and developing strategies to help the early diagnoses and management of some ocular conditions. The aim of this study was to determine the CCT and ACD of adults in a Nigerian population and also investigate the correlations between them in the study population.
Materials and Methods: Sixty-six individuals consisting of 31 males and 35 females between 18 and 68 years participated in this study. The CCT and ACD were measured with ultrasound pachymetry and ultrasonography (PacScan 300, Sonomed International Corp., USA). Data were analyzed with Statgraphics Plus (Statistical Graphics Corp., USA) and SPSS version 22.0 (SPSS Inc., Chicago, IL, USA) software.
Results: The mean age, CCT, and ACD were 37.2 ± 11.6 years, 536.71 ± 23.89 μm, and 3.30 ± 0.32 mm, respectively. The CCT and age showed a negative trend, not statistically significant (P = 0.12). Regression analysis performed on ACD and age showed an inverse correlation (P < 0.0001). There was no difference (P > 0.05) in mean CCT between males (536.7 ± 28.38 μm) and females (536.71 ± 19.50 μm). Similarly, there was no difference in mean ACD between males (3.36 ± 0.34 mm) and females (3.24 ± 0.3 mm) although not statistically significant (P = 1.48).
Conclusion: There was no statistically significant correlation between CCT and ACD, and a prediction of approximately 0.10-mm decrease in ACD and approximately 4.0-μm decrease in CCT per decade was made.
Keywords: Anterior chamber depth, central corneal thickness, pachymetry, ultrasonography
|How to cite this article:|
Iyamu E, Okukpon JO, Uduoise I. The central corneal thickness and anterior chamber depth of adults in a Nigerian population. Albasar Int J Ophthalmol 2018;5:6-11
|How to cite this URL:|
Iyamu E, Okukpon JO, Uduoise I. The central corneal thickness and anterior chamber depth of adults in a Nigerian population. Albasar Int J Ophthalmol [serial online] 2018 [cited 2021 Jul 29];5:6-11. Available from: https://www.bijojournal.org/text.asp?2018/5/1/6/289594
| Introduction|| |
The cornea is the most anterior refractive surface of the optical system of the eye, and together with the anterior chamber and the lens, it refracts light, accounting for approximately two-thirds of the eye's total optical power. The cornea is also the transparent front part of the eye that covers the iris, pupil, and anterior chamber. The measurement of the central part of the cornea is an important indicator of cornea health, known as central corneal thickness (CCT), and it is a highly heritable trait proposed to influence disorders of the anterior segment of the eye. CCT plays an important role in both the diagnostic/therapeutic assessment of glaucoma and corneal diseases, contact lens use, and in refractive surgery.,
The anterior chamber depth (ACD) lies between the posterior surface of the cornea that is the corneal endothelium and the iris. The average of the ACD gives information on the anterior/equatorial growth of the eye. The ACD measurement is useful in ophthalmic practice, for instance, in cataract and refractive surgery, intraocular lens power and diameter, and screening for glaucoma risk factors.
For several years, ultrasound pachymeters and ultrasound biometers have been used to study CCT and ocular ACD, which were used in this study to assess the CCT and ACD.,,, The measurement and fundamental understanding of CCT and ACD is important because these parameters play an important role in the early diagnosis of glaucoma by ensuring proper intraocular pressure (IOP) correction. The aim of this study was to determine the CCT and ACD of adults in a Nigerian population and also investigate the correlations between the two parameters. The result of this study will further aid research in early diagnoses of some ocular morbidity by identifying risk factors associated with these parameters in this population.
| Materials and Methods|| |
This was an observational, prospective, cross-sectional study to determine the relationship between CCT, axial length, and vitreous chamber depth. The participants were recruited after detailed optometric examination that included best-corrected visual acuity, refraction, slit-lamp examination, applanation tonometry, and fundus examination. Only Nigerians who had no ocular disease, no previous ocular surgery, normal IOP, normal blood pressure, and refractive error ≤±0.50 D and participants without comorbidities affecting CCT such as diabetes mellitus were included in the study. Exclusion criteria included previous ocular surgery (any type of eye surgery), glaucoma, trauma history, external eye disease, extensive pterygium, corneal edema or dystrophy, aphakia, amblyopia, and lack of cooperation.
The study was approved by the ethics and research committee in accordance with the tenets of the Helsinki Declaration involving human participants, and informed consent was obtained from all patients.
Measurements were taken on the right and left eye of each participant throughout this research after sterilization of the probe. The participant was comfortably seated with the head upright and ayes in the primary position of gaze. The probe was sterilized with 70% alcohol and allowed to air-dry before each use and between measurements. A drop of topical anesthetic (Tetracaine HCl 0.1%) was instilled in the participant's eye. The probe was carefully aligned perpendicularly to and lightly applanating the cornea.
Central corneal thickness
Sterilized ultrasound pachymeter probe (speed: 1640 m/s and frequency: 20 MHz) was used to determine the CCT. The probe will be carefully aligned perpendicularly to and lightly applanating the anesthetized cornea. Five readings were continually taken, and the average was calculated by the instrument as measured CCT.
Anterior chamber depth
Sterilized A-scan ultrasound biometer probe (speed: 1548/ms and frequency: 10 MHz) was used to determine the ACD. The probe will be carefully aligned perpendicularly to and lightly applanating the anesthetized cornea. Five readings were continually taken, and the average was calculated by the instrument as measured ACD.
All data obtained were analyzed with Statgraphics Plus (Statistical Graphics Corp., USA) and SPSS version 22.0 (SPSS Inc., Chicago, IL, USA). Measures of spread including standardized kurtosis and standardized skewness were derived. The measured variables (CCT, spherical equivalent refractive error, and ACD) were tested for normality with the Kolmogorov–Smirnov Z-test (normal distribution when the lower P > 0.05). Analysis of variance was used to compare the variables across the age groups and post hoc test for pair-wise comparison within the groups. Gender-related differences in measured variables were tested with Student's t-test (unpaired). The correlation or association between variables was tested using regression analysis. P < 0.05 was considered statistically significant.
| Results|| |
A total of 66 (n = 66) participants (132 eyes) aged between 18 and 68 years with a mean age of 37.2 ± 11.6 years, consisting of 31 males and 35 females, had participated in this study [Table 1].
Mean anterior chamber depth, central corneal thickness, and the effect of age
Regression analysis performed on ACD and age showed a statistically significant inverse correlation (r = −0.45, r2 = 19.9%, P < 0.0001). The linear regression model is represented by: ACD = 3.761–0.013 age. The model as fitted explains 19.9% of the variability in ACD. From the regression model, a prediction of approximately 0.10-mm decrease in ACD can be made. [Figure 1] shows the correlation of ACD on age and the linear regression line. The linear regression model is represented by: CCT = 551.7–0.404 age [Figure 2]. The model as fitted explains 3.8% of the variability in CCT. From the regression model, a prediction of approximately 4.0-μm decreases in CCT per decade can be made.
|Figure 1: Correlation of anterior chamber depth and age with the linear regression line with 95% confidence interval of the regression line|
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|Figure 2: Correlation of central corneal thickness and age with the linear regression line with 95% confidence interval of the regression line|
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Association between mean central corneal thickness and anterior chamber depth
Regression analysis performed on CCT and ACD showed no statistically significant correlation (P = 0.47). The linear regression model was represented by: CCT = 558.92 − 6.738ACD [Table 2].
Effect of gender on central corneal thickness and anterior chamber depth
The difference in the mean age between males and females was not statistically significant (unpaired t-test: t = 1.09, Degree of freedom = 64, P = 0.28). There was no difference in the mean CCT between males and females (P > 0.05). Similarly, there was also no difference in the mean ACD between males and females (P = 1.48) [Table 3].
| Discussion|| |
CCT and ACD have become a very important parameter of study due to their importance in the diagnosis of a number of ocular diseases and as an indicator in glaucoma risk factor. CCT measurement is important for ensuring proper IOP correction in individuals with increased glaucoma risk, whereas ACD measurement is important for its correlation with axial length and its association with increased risk for angle closure if the anterior angle is shallow. In this present study, CCT and ACD were measured to establish their distribution and their correlations in the Nigerian population.
The mean CCT from our study represented in [Table 1] was higher than the mean CCT reported by some other researchers,,,,,,, but was closely in line with that of Osuobeni et al., Doughty and Zaman, Mercieca et al., and Iyamu and Okukpon. They reported a mean CCT of 535 ± 35.1, 536.0 ± 31, 535.0 ± 38, and 536.71 ± 23.89, respectively. These results also showed a lower CCT in some studies [Table 4].,,,,
The correlation between CCT and age showed a negative trend, though not statistically significant was also comparable with the findings of Iyamu et al. and Wong et al. They also observed a negative but significant correlation between CCT and age (r = −0.25, P = 0.021; r = −0.237, P < 0.05, respectively); similar findings were recorded in other researchers work,,,, who reported that there was no significant association between CCT and age in healthy participants.
The mean ACD [Table 4] in this study was higher than the mean ACD reported by some other studies,,, but lower than that of the results of some researchers, of ACD, although similar to reports of some studies.,,,, Regression analysis performed on ACD and age showed a statistically significant inverse correlation (r = −0.45, P < 0.0001). An increase in age correlated with a mean 0.011 mm/year decrease in ACD was found in this study, ACD also decreased by 0.013 mm/year according to Hashemi et al. Atchison et al. also found that ACD decreased significantly with age at a rate of 0.011 mm/year, similar to the study of Dubbelman et al., with a rate of −0.010 mm/year and Koretz et al. at −0.011 mm/year. The result in this study on ACD correlation with age was similar to that of Hosny et al. (−0.391, −0.623, P < 0.01), Mashige and Oduntan (r = −0. 72, P < 0. 001), Mohamed et al. (r = −0.391), Fahmy (r = −0.307, P < 0.001), Hashemi et al. (r = −0.014, P < 0.001), and Eysteinsson et al. (r = −0.013, P < 0.001). All these authors have concluded that ACD correlated inversely with patient's age.
Regression analysis performed on CCT and ACD showed that CCT did not correlate with ACD. This was in line with a number of studies.,, They concluded that CCT was an independent factor unrelated to other ocular parameters. Yebra-Pimentel et al. did not agree with this result, and they reported that ACD showed a significant statistical correlation with CCT.
There was no difference in mean CCT between males and females (P > 0.05) in this study. There was no statistical proof of influences on the CCT values on gender and age in this study. This is similar to the reports of numerous studies,,,,,,,,,,,, and they found no significant difference in CCT between men and women. The finding of this study was not in agreement with some other studies,,,,, and they suggested a gender difference in ocular biometrics with women having a significantly thinner cornea and in some other studies,, males having thicker corneas than females, but differences were not statistically significant. The gender-related differences in ACD were statistically significant after adjusting for height (P < 0.0001). A number of studies,,,,,,,,, have found significantly deeper ACD for males of up to 0.18 mm similar to the results in this study. On the other hand, Sanhermelando et al., Chen et al., and Atchison et al. did not find a significant effect of gender on ACD. Previous researchers,, have suggested that the gender differences in these parameters could be due to the fact that men are generally taller than women.
| Conclusion|| |
The measurement of CCT and ACD has been shown to be a critical procedure in many clinical situations. This study showed that there was no statistically significant correlation between CCT and ACD. From the regression model, a prediction of approximately 0.10-mm decrease in ACD and a prediction of approximately 4.0-μm decrease in CCT per decade can be made. ACD measurement should be encouraged routinely, especially in older patients, as regression analysis performed on ACD and age showed a statistically significant inverse correlation. The measurement of CCT which cannot be overemphasized should be inculcated into routine examination, especially on a regular basis, as this is an important determinant in many ocular disorders such as glaucoma. The findings of this study can be used as a reference for diagnostic and clinical purposes.
The authors wish to thank Rachel Eye Centre, Area 11, Garki, Abuja, for granting the permission to use their facility for this study.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4]