|Year : 2021 | Volume
| Issue : 3 | Page : 269-273
Central corneal thickness, anterior chamber depth, and axial length in patients with type II diabetes mellitus
Namrata Sasalatti, Rajani Kadri, Sudhir Hegde, Ajay A Kudva, P Devika, Akansha Shetty, Prerana Shetty
Department of Ophthalmology, A. J. Institute of Medical Sciences and Research Institute, Mangalore, Karnataka, India
|Date of Submission||20-Nov-2020|
|Date of Decision||08-Feb-2021|
|Date of Acceptance||22-Feb-2021|
|Date of Web Publication||08-Dec-2021|
Plot No C-11, Sector No - 34, Opposite Police Palace, Navanagar, Bagalkot Karnataka 587103
Source of Support: None, Conflict of Interest: None
Purpose: The aim of this study was to study the central corneal thickness (CCT), anterior chamber depth (ACD), and axial length (AL) in patients with type II diabetes mellitus and compare it with healthy controls. Methods: A hospital-based nonrandomized prospective comparative study was conducted on 50 type II diabetics and 50 healthy controls. Complete ophthalmic examination was performed. CCT was measured using an ultrasound pachymeter, ACD, and AL was measured using an optical biometer. Statistical comparisons were done between the cases and controls. Results: The mean CCT in diabetic group was significantly higher (531.00 ± 33.42 μm) compared to control group (505.70 ± 32.19 μm) (P < 0.001) The mean ACD in diabetics (3.19 ± 0.35 mm) was significantly lesser compared to healthy control (3.78 ± 0.10 mm) (P < 0.001). CCT and ACD values between subgroups of diabetics such as duration of diabetes, grade of retinopathy, HBA1C values were statistically not significant (P > 0.05). AL s were comparable between the two groups. Conclusion: Patients with type 2 diabetes mellitus in our study had a thicker CCT and shallow anterior chamber regardless of retinopathy status, duration of diabetes mellitus, glycemic control.
Keywords: Anterior chamber depth, axial length, central corneal thickness, diabetes mellitus
|How to cite this article:|
Sasalatti N, Kadri R, Hegde S, Kudva AA, Devika P, Shetty A, Shetty P. Central corneal thickness, anterior chamber depth, and axial length in patients with type II diabetes mellitus. Kerala J Ophthalmol 2021;33:269-73
|How to cite this URL:|
Sasalatti N, Kadri R, Hegde S, Kudva AA, Devika P, Shetty A, Shetty P. Central corneal thickness, anterior chamber depth, and axial length in patients with type II diabetes mellitus. Kerala J Ophthalmol [serial online] 2021 [cited 2022 Jan 19];33:269-73. Available from: http://www.kjophthal.com/text.asp?2021/33/3/269/331934
| Introduction|| |
Diabetic keratopathy is a known entity that affects approximately 70% of diabetic population and includes decrease in corneal endothelial cell density (CED) and hexagonality, polymegathism, pleomorphism, increase in CCT, higher corneal autofluorescence, and lower corneal sensitivity., Central corneal thickness (CCT) is an important measurement for the diagnosis, treatment, and management of various ocular conditions and also a sensitive indicator for endothelial physiology and functions., CCT has a positive correlation with intraocular pressure (IOP) measured by Goldmann Applanation tonometry and this effect on measured IOP can be clinically significant. Thicker CCT in diabetes mellitus should be taken into consideration while measuring IOP in diabetics.
Diabetic subjects are at higher risk of glaucoma. Diabetes can decrease anterior chamber depth (ACD)., which can be a predisposing factor for the development of angle-closure glaucoma. Measurement of ACD acts as a valuable tool for the prediction and diagnosis of primary angle-closure glaucoma. Diabetes also has a positive association with open-angle glaucoma., and may affect axial length (AL) and spherical equivalent.,, Short AL has been associated with diabetes and diabetic retinopathy. This study was conducted to assess the corneal thickness, ACD, and AL in diabetic subjects and compare it with that of healthy controls.
| Materials and Methods|| |
This prospective, hospital-based, comparative study protocol was approved by the university's institutional ethical committee. Our study was conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from all the patients before their enrolment in this study. The diagnosis of Diabetes mellitus was based on the criteria of the American diabetic association (ADA). Recruitment of the subjects was based on medical history and treatment taken by the patients attending the outpatient department. Nondiabetic patients taken as controls underwent two random blood glucose tests in accordance with the recommendations of the ADA to disclose undetected diabetes.
The inclusion criteria for the study are patients willing to give written informed consent, patients age >40 years, patient's diagnosed as type II diabetes at least 1 year before the study, and started on antidiabetic drugs. The exclusion criteria included patients not willing to give written informed consent, postoperative patients, patients with corneal diseases and dystrophies, type I diabetes, contact lens users, any ocular trauma such as blunt and penetrating injuries, history of any other systemic illness, patients with glaucoma and retinal diseases not associated with diabetes, any other ocular diseases such as dry eye, anterior uveitis, primary angle-closure glaucoma, evidence of any corneal pathology on slit-lamp biomicroscopy and high refractive errors. For standardization, the right eye of all the subjects was examined. The patient was positioned on a chair in front of the devices till the instruments automatically took an image of various parameters mentioned above. The ocular examination included slit-lamp anterior segment examination, grading of the lens nuclear sclerosis (according to Lens Opacity Classification System III), IOP was measured using Goldmann applanation tonometer, dilated fundus examination using slit-lamp biomicroscopy (90D), indirect ophthalmoscopy, and fundus photography if required. Subjects were examined using optical biometer (Tomey OA-2000) for ACD, AL measurement, and noncontact specular microscope Tomey EM– 4000 (Tomey Corporation, japan) for CCT measurement.
Sample size estimation-Based on a previous study by Ozdamar et al. the difference in means of CCT was 26 and standard deviation of cases was 30 and standard deviation of controls was 35, with the alpha error being 0.01 and the power of study 90% (beta error– 0.10), the minimum number of sample required in each group would be 50.
The sample size was calculated using Med CalcVersion 14.8-1993-2014, Med calc software bvba.
Statistical analysis: The data were analyzed using the statistical package for social sciences (SPSS 17 version) (SPSSINC., 233 South Wacker Drive, 11th floor, chicago). The normal distribution of variables was assessed using the Kolmogorov–Smirnov test (P < 0.05 indicated that the data were not normally distributed). Results were presented as mean ± standard deviation, median and interquartile ranges are presented for parameters (CCT, ACD, AL). Repeated analysis of variance was used for comparison of the mean. A-scan biometry between the case and control, the association between the various parameters were studied using linear regression analysis. P < 0.05 was considered significant.
| Results|| |
In this study, 50 type II diabetic cases were compared with 50 healthy controls. The mean age of all recruited patients was 56.36 ± 9.66 years. [Table 1] details the distribution of cases and controls with respect to age, gender, IOP, HbA1C. The mean CCT in diabetics 531 (±33.42) μm was significantly thicker than the CCT of healthy controls 505.70 (±32.19) μm (P < 0.01). CCT was increased in cases with diabetes more than 11 years however this was not statistically significant (P = 0.808) as represented in [Table 2]. [Table 3] details the mean anterior ocular segment biometry between the groups. The mean ACD in diabetics was 3.19 (±0.35) mm compared to 3.78 (±0.10) mm in healthy controls, the difference was statistically significant (P < 0.001). The AL between the two groups, diabetics, and healthy controls were comparable. IOP, CCT, ACD, and AL between subgroups of diabetics such as duration of diabetes, IOP, Hemoglobin A1C (HbA1C) values were statistically not significant (P > 0.05). [Table 4] gives the coefficients from linear regression analysis between age, sex, duration, HbA1C with IOP, CCT, ACD, AL in cases. Lens sclerosis was significantly associated with ACD. [Table 2] and [Table 5] represent the comparison of CCT with the duration of diabetes and HbA1c levels respectively.
|Table 1: Distribution of subjects with respect to age, gender, intraocular pressure, and random blood sugar|
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|Table 2: Comparison of central corneal thickness with duration of diabetes|
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|Table 3: Comparison of mean anterior ocular segment biometry findings between the groups|
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|Table 4: Linear regression analysis between age, duration, sex, hemoglobin A1c (independent variables) with intraocular pressure, central corneal thickness, anterior chamber depth, axial length (dependable variables ) in cases|
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|Table 5: Comparison of central corneal thickness with hemoglobin A1c values|
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| Discussion|| |
Diabetic keratopathy implies spectrum of changes occurring in the cornea of diabetic patients. In our study, patients with type 2 diabetes mellitus had a thicker cornea and shallow anterior chamber that had no association with duration of the disease, diabetic retinopathy, or glycemic control.
The relation between CCT and diabetes mellitus has been reported differently in various studies. In our study, we found that diabetic patients had significantly thick corneas than nondiabetics. Reduction of Na + K + ATPase activity due to increased sugar levels directly inhibits the corneal endothelial pump function increasing stromal hydration and intracellular accumulation of sorbitol, an osmotic agent causes corneal hydration in diabetics. Recent studies suggesting advanced glycosylated end product acting as cross-linking agents to increase the covalent bond in the corneal stroma and eventually its thickness and gradual stiffening of the cornea and consequently affect the accuracy of IOP measurements.
Many studies have showed diabetics to have increased CCT.,,, However, in a study conducted by Inoue et al., Wiemer et al. CCT in diabetic patients was comparable with that of nondiabetic patients.
In our study, we found that ACD in diabetes was shallower compared to the controls which was similar to the study by Saw et al. where cases with diabetes had shallower anterior chambers and thicker lenses (4.88 vs. 4.75 mm, P = 0.003). Reduction in ACD in diabetes patients supports the concept that the disease may be a risk factor for the development of acute angle closure.
Increasing lens thickness and decreasing ACD in diabetics have been confirmed in a population-based twin study and it was also found that ACD was negatively correlated with the duration of diabetes. Although we did not observe any correlation between the duration of the disease and anterior segment parameters, diabetics had a significant association of lens thickness with the IOP and ACD. Measurement of ACD in diabetics may aid in the early detection and management of angle-closure glaucoma. In our study , there was no significant influence of HbA1c levels on central corneal thickness, anterior chamber depth and axial length , parameters being mentioned in [Table 5].
Pierro et al. in their study showed that diabetic patients presented shorter ALs compared with the controls. Significantly shorter ALs were found in the background and proliferative retinopathy groups compared with the group without retinopathy and no difference in AL was found between the diabetic patients without retinopathy and the on diabetic subjects. In our study, AL measurements were comparable between the two groups. The absence of association of the anterior segment parameters with duration and glycemic status needs further evaluation as the changes in diabetics could be a transient phenomenon occurring during increased blood sugars.
Limitations of this study included (a) Myopic and hyperopic refractive shifts in diabetic patients which have been related to changing plasma glucose concentration could not be assessed as refractive values were not taken into account. (b) CCT was taken into account while peripheral corneal thickness was not, hence the need for further studies measuring both the corneal thickness. (c) Effect of diurnal variation on CCT due to variation of plasma blood glucose levels was not assessed. (d) Only right eye being considered for measurements in this study, possible interocular differences in the parameters could not be accounted for.
| Conclusion|| |
Thicker central cornea and shallow anterior chamber were found in patients with diabetes mellitus than that of healthy controls. CCT is pivotal in refractive surgeries, glaucoma workup, donor tissue evaluation before keratoplasty, and long-term contact lens users. A simple noninvasive test in form of pachymetry helps in the identification of those patients with diabetes who could be at higher risk of developing ocular complications, enabling better control of disease. A shallow anterior chamber seen in diabetes can be used as a screening tool in the diagnosis of angle-closure glaucoma.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]