[Variation of central corneal thickness in diabetic patients as detected by ultrasonic pachymetry]

Innate Immune System Activation, Inflammation and Corneal Wound Healing

Corneal wounds resulting from injury, surgeries, or other intrusions not only cause pain, but also can predispose an individual to infection. While some inflammation may be beneficial to protect against microbial infection of wounds, the inflammatory process, if excessive, may delay corneal wound healing. An examination of the literature on the effect of inflammation on corneal wound healing suggests that manipulations that result in reductions in severe or chronic inflammation lead to better outcomes in terms of corneal clarity, thickness, and healing. However, some acute inflammation is necessary to allow efficient bacterial and fungal clearance and prevent corneal infection. This inflammation can be triggered by microbial components that activate the innate immune system through toll-like receptor (TLR) pathways. In particular, TLR2 and TLR4 activation leads to pro-inflammatory nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) activation. Similarly, endogenous molecules released from disrupted cells, known as damage-associated molecular patterns (DAMPs), can also activate TLR2, TLR4 and NFκB, with the resultant inflammation worsening the outcome of corneal wound healing. In sterile keratitis without infection, inflammation can occur though TLRs to impact corneal wound healing and reduce corneal transparency. This review demonstrates the need for acute inflammation to prevent pathogenic infiltration, while supporting the idea that a reduction in chronic and/or excessive inflammation will allow for improved wound healing.

Effect of diabetes mellitus on quantitative corneal anatomy – A systemic review

Background: Corneal changes occur as a direct consequence of diabetes mellitus (DM). The central corneal thickness (CCT) is a useful parameter that provides information about the status of the metabolism of the cornea and can therefore help monitor the progression of DM.Aim: The aim of this study was to determine the impact of DM on CCT and its correlation with diabetes duration and glycated haemoglobin (HbA1c) levels.Methods: The systematic review was undertaken to answer: (1) What effect does DM have on CCT values? (2) What effect does DM duration have on CCT values? (3) What effect does HbA1c levels have on CCT values? The Web of Science was used to conduct a computerised search for articles of CCT values in DM.Results: A total of 38 articles that met the criteria for inclusion were included in this systemic review. The researchers found 27 articles that observed increased CCT values in DM patients compared with control subjects. There were six studies in which increased CCT values were related to DM duration and 12 studies in which DM duration did not alter CCT values. Also, eight studies showed that CCT values increased with glycated haemoglobin levels, and 12 studies did not observe this.Conclusion: Diabetes mellitus patients usually present with increased CCT values although there is no unanimity about the effect of DM duration and increased HbA1c levels (poor glycaemic control) in the CCT values of DM patients. 

Association of severity of diabetic retinopathy with corneal endothelial and thickness changes in patients with diabetes mellitus

OBJECTIVE

To analyse the central corneal thickness, endothelial cell density and morphology in patients with diabetes mellitus (DM).

METHODS

We analysed corneal endothelium, i.e. central corneal thickness (CCT), endothelial cell density (ECD), coefficient of variation in cell size (CV), and hexagonality (Hex) with specular microscopy in patients with type 2 DM and compared with age-matched controls. The influence of diabetic retinopathy (DR) severity, duration of DM, and level of glycosylated haemoglobin (HbA1c) was also analysed.

RESULTS

The study cohort included 592 eyes of 592 diabetic patients and 596 eyes of 596 control subjects. A significant difference was found in CCT (522.1 ± 36.6 μm in DM, 514.9 ± 37.1 μm in controls; P = 0.001), ECD (2484.5 ± 299.5 cells/mm² in DM, 2555.9 ± 258.2 cells/mm² in controls; P = 0.017), CV (40.3 ± 6.1 in DM, 37.2 ± 6.1 in controls; P < 0.001) and Hex (39.9 ± 5.2 in DM, 44.6 ± 6.0 in controls; P < 0.001). The longer duration of DM ( > 10 years) and poor glycaemic control (HbA1c > 7.5%) were associated with similar results. A significantly reduced ECD (P < 0.001) and Hex (P = 0.001) and higher CV (P = 0.007) and CCT (P = 0.01) was noted when assessed against various stages of DR. Multivariate analysis showed that increasing age was significantly associated with lower ECD (P < 0.001), Hex (P < 0.001), and CCT (P = 0.004); and a higher CV (P < 0.001).

CONCLUSIONS

DM has deleterious effects on corneal endothelium and thickness. The presence of DR may further warrant a thorough corneal evaluation, especially when planning intraocular surgery.

Effect of Insulin Therapy on Ocular Biometric Parameters in Diabetic Patients

Purpose: To evaluate effects of insulin on ocular parameters in patients with type 2 diabetes mellitus who start insulin therapy. Methods: In this prospective study, ocular biometric parameters were obtained using optical biometer (Lenstar LS900^®; Haag-Streit AG) and refraction test (ARK-510A Auto refracto-keratometer; Nidek Co. Ltd, Aichi, Japan) before and at 3 months after initiating insulin therapy. In addition, patients' fasting blood glucose (FBG), glycosylated hemoglobin (HbA1C), and blood lipid levels were measured at the same time points. Pretreatment and post-treatment results were compared. In addition, associations between ocular parameters with initial dose and type of insulin treatment regimen, HbA1C, and FBG levels were evaluated. Results: The patients' mean age was 51.2 ± 12.9 (18-73) years. Post-treatment HbA1C and FBG levels (8.5% ± 2.5% and 188.1 ± 111.2 mg/dL, respectively) were significantly lower than pretreatment values (12% ± 1.4% and 325.3 ± 95.7 mg/dL, respectively; P < 0.001 for both). There was a significant positive correlation between the change in HbA1C and the change in lens thickness (P = 0.03), and a significant negative correlation between the change in FBG and the change in the spherical equivalent refraction (P = 0.045). Insulin dose and treatment regimen type were not significantly correlated with ocular parameters (P > 0.05). Conclusion: HbA1C-lowering glycemic effect of insulin was correlated with a small decrease in lens thickness. Long-term, randomized controlled trials including larger patient numbers are needed to shed light on the long-term effects of insulin use and glycemic control on ocular parameters.

Association of Diabetes With Central Corneal Thickness Among a Multiethnic Asian Population

IMPORTANCE

Thicker or thinner central corneas may lead to either overestimation or underestimation of intraocular pressure, which is the most important causal and treatable risk factor for glaucoma. However, the findings on the associations between diabetes, random glucose, and glycated hemoglobin A1c (HbA1c) with central corneal thickness (CCT) are conflicting.

OBJECTIVE

To evaluate the associations between diabetes, random glucose, and HbA1c with CCT in a multiethnic Asian population.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional analysis of the Singapore Epidemiology of Eye Diseases (SEED) Study conducted from 2004 to 2011. A total of 10 033 Chinese, Malay, and Indian individuals 40 years or older residing in Singapore were recruited. Participants with incomplete information on diabetes status (448 participants), prior refractive or cataract surgery (1940 eyes), and corneal edema or dystrophy (29 eyes) were excluded. A meta-analysis was conducted to estimate the overall association of diabetes with CCT.

EXPOSURES

Standardized clinical examinations and interviewer-administered questionnaire to collect information about demographic, systemic, and ocular factors.

MAIN OUTCOMES AND MEASURES

Measurement of CCT using ultrasound pachymetry.

RESULTS

A total of 8846 adults (mean [SD] age, 57.9 [9.9] years; 4447 women [50.3%]) (17 201 eyes) were included in the final analyses. The CCT profile was similar among participants with and without diabetes (mean [SD] CCT, 545.3 [33.7] μm vs 544.8 [33.9] μm; P = .39). Following adjustments of age, sex, ethnicity, corneal curvature, axial length, and body mass index, CCT was a mean (SD) of 4.9 (0.8) μm (95% CI, 3.3-6.5 μm) thicker in patients with diabetes than those without diabetes. Multivariable analyses also showed that thicker CCT was associated with higher random glucose (per 10 mg/dL [to convert to mmol/L, multiply by 0.0555], β = 0.3; 95% CI, 0.2-0.4) and higher HbA1c (per percentage, β = 1.5; 95% CI, 1.0-2.1) (all P < .001). These associations were significant in the subgroup with diabetes but not in the subgroup without diabetes. A meta-analysis including 12 previous population- and clinical-based studies showed that CCT was 12.8 μm (95% CI, 8.2-17.5 μm) thicker in eyes of patients with diabetes.

CONCLUSIONS AND RELEVANCE

These findings suggest that diabetes and hyperglycemia were associated with thicker CCT. This study provides useful information on the interpretation of intraocular pressure in patients with diabetes.

Diabetes and pachymetry changes in pregnancy

BACKGROUND

Purpose of this study is to evaluate changes in the central corneal thickness (CCT) in patients during the third trimester and postpartum phases of normal pregnancy, pregestational diabetes mellitus (DM), and gestational diabetes mellitus (GDM).

METHODS

This was a prospective study. Patients that fulfilled the inclusion criteria were recruited from the obstetric clinic. They were grouped into normal pregnancy, pregestational DM, and GDM. Ophthalmic assessment and haematological investigations were done during the third trimester (after 28 weeks of gestation) and in the postpartum phase (6 weeks postpartum).

RESULTS

A total of 192 pregnant patients were recruited for this study. Out of the 192 patients, only 143 of them came back for their follow-up 6 weeks postpartum. A total of 70 (36.5%) normal pregnancy patients, 51 (26.6%) DM patients, and 71 (36.9%) GDM patients were included in this prospective study. Our study showed that the CCT decreased postpartum in all three groups. Patients in all three groups did not have significantly different CCT during the third trimester of pregnancy and postpartum phase. However, patients who had thicker CCT irrespective of the grouping during the third trimester also had a thicker CCT post-delivery (p value <0.001). However, these changes did not appear to affect refractive error and visual acuity.

CONCLUSIONS

Diabetes mellitus during pregnancy did not appear to influence the CCT.