Changes of extracellular matrix of the cornea in diabetes mellitus

Differences in corneal viscoelasticity due to diabetes have been reported to have a protective effect on the progression of glaucoma and the development and progression of keratoconus. Due to longterm changes of tissue in diabetes mellitus, biomechanical changes of the cornea because of glycation and modified extracellular matrix may be detectable. The purpose of the study was to determine whether there is a difference in corneal biomechanical properties, characterized by corneal hysteresis (CH) and central corneal thickness (CCT), between diabetic and normal subjects, and relate these to the duration of diabetes.

In a cross sectional study, a group of 484 eyes including 99 eyes of diabetic individuals was evaluated. CH as measured with the Ocular Response Analyzer, CCT (Orbscan II), Goldmann applanation tonometry (GAT) and slit-lamp examination were obtained from each patient. Linear mixed models were applied for statistical evaluation.

CH showed a significant decrease with age (-0.036 mmHg/year, p < 0.01) while CCT increased significantly (+0.7 microm/year, p < 0.001). CH was significantly higher in diabetic eyes with an average difference of +0.55 mmHg (after correcting for age, IOP and CCT). This was not related to the duration of diabetes (mean 12.6 +/- 9.0y, p = 0.522). CCT did not differ with regard to diabetes. Intraclass correlation coefficients were 81% and 50% for CCT and CH respectively.

CH is assumed to be an indicator for acquired changes of tissue such as diabetes-mediated. CCT is a more characteristic parameter for the individual patient. CH may provide more information about changes of the extracellular matrix in diabetes, and therefore offer a new monitoring parameter.