Small Fluctuations in Limbal Thickness are Associated with Blood Glucose Values in Young Healthy Subjects

Abstract

Purpose: Previously our group has reported in cross sectional data that limbal thickness (LT) values are positively associated with blood glucose (BG) measures in low myope controls (under-5.50D). This association is absent in patients with diabetes of the same Rx range and higher myopes with thinner scleras. The timeline of these structural changes and the mechanism behind this remains unclear. Here we follow up with a longitudinal pilot study. It seeks to both confirm that these short term fluctuations in LT with BG changes occur within individuals and to learn more about the scale of these differences.<br />

Methods: Eighteen 24-32 years old were recruited for this portion of the study. There were 2 high myopes, 9 low myopes, and 6 essential emmetropes. OCT of the temporal sclera at the limbus was performed (Heidelberg Spectralis SD-OCT AS module lens) and LT was measured on the more myopic eye. BG was taken directly before. Two measurements of LT and BG were taken at different times of day but within the same week. The differences between the measures were evaluated.

Results: Within individuals, short term differences in BG were positively associated with differences in LT (p<0.03), 78% of patients exhibited this trend. Of the 4 who did not; 2 are the high myopes and a third is a -5D myope. This furthers the data that high myopes may not experience these same fluctuations in LT with BG changes due to scleral differences. This new data is in-line with the cross sectional results previously gathered. The scale of the LT fluctuations was highly variable between subjects but typically small, 7 ± 30 microns. <br />

Conclusions: These results confirm short term structural changes at the limbus, which are tied to systemic BG values and measurable with AS-OCT in low myopes. Evaluation of these changes in vascular conditions such as diabetes as well as higher myopia is warranted as a follow up to this work. It appears that higher myopes with thinner scleras may not exhibit this trend. Further investigation into the mechanism at a more detailed level would aid in this analysis.