PURPOSE: To determine how changes in corneal elasticity/stiffness might influence intraocular pressure (IOP) readings in diabetic patients. METHODS: A systematic review of the literature was performed to understand the conflicting relationship between diabetes, elevated IOP, and glaucoma progression. RESULTS: Diabetic patients have been found to have statistically significant higher IOP readings in some population-based studies compared to non-diabetics. Insulin resistance states, hyperglycemia and glycosylated hemoglobin have been correlated with higher IOP (1 mmHg) measurements in diabetic patiente. In the Ocular Hypertension Treatment Study (OHTS), a self reported history of diabetes was found to be protective against the progression of primary open-angle glaucoma. Small differences in IOP measurements in diabetic patients may be due to corneal stiffening, as demonstrated by the protective effect of glucose-mediated collagen cross-linking against the manifestation and keratometric progression of keratoconus. Different collagen cross-linking agents may induce different degrees of corneal stiffening, which can result in differences in measured IOP. CONCLUSIONS: Glucose-mediated corneal stiffening due to collagen cross-linking might be responsible for IOP overestimation in diabetic patients. Corneal stiffening might explain why diabetic eyes lend to have higher IOP readings in large population-based studies and why those with ocular hypertension have a reduced risk for glaucoma progression.
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