• More Evidence That Diabetes Is Linked to Greater CCT

    By Lynda Seminara
    Selected By: Deepak P. Edward, MD

    Journal Highlights

    JAMA Network Open
    2019;2(1);e186647

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    High intraocular pressure (IOP) is the most treatable risk factor for glaucoma, but the degree of central corneal thickness (CCT) may impede accurate estimation of IOP. Research on links between diabetes and CCT has pro­duced conflicting results, and few stud­ies have addressed the effect of serum glucose or hemoglobin A1c (HbA1c) on the cornea. In a cross-sectional analy­sis of the Singapore Epidemiology of Eye Diseases (SEED) study, Luo et al. observed a correlation between thicker CCT and the presence of diabetes or hyperglycemia.

    This study included 8,846 adults aged 40 years or older (mean, 58 years), who were of Chinese, Malay, or Indian ethnicity. The researchers also performed a meta-analysis—which included 12 previous clinical and population-based studies—to estimate the overall association of diabetes with CCT. Standardized clinical exams were conducted, and questionnaires were administered to collect demographic, systemic, and ocular information. The main outcome was CCT, measured using ultrasound pachymetry.

    The CCT profile of participants with and without diabetes was similar (mean CCT, 545.3 vs. 544.8 μm, respectively; p = .39). After adjusting for age, sex, ethnicity, corneal curvature, axial length, and body mass index, the mean CCT was 4.9 μm greater for patients with di­abetes. According to the meta-analysis, CCT was 12.8 μm greater in patients with diabetes. Multivariable analyses showed that greater CCT also was associated with higher levels of random glucose readings (per 10 mg/dL, β = 0.3; p < .001) and higher HbA1c (per percentage, β = 1.5; p < .001). These associations were significant for pa­tients with diabetes but not for those without diabetes.

    Findings of this study may be useful for estimating CCT more accurately. Strengths of this research include the large sample size and use of standard­ized assessments, enabling adjustment for potential confounders and substan­tiating the validity of findings. Study limitations include the lack of fasting glucose measurements.

    As a result, the authors recom­mended caution when interpreting the findings, and they acknowledged that further research is needed to explore causal factors for the associations.

    The original article can be found here.