gms | German Medical Science

Changes in the biomechanical properties of the lamina cribrosa (LC) and of the peripapillary sclera might play a role in the pathogensis of glaucoma. Glyceraldehyde and methylglyoxal are precursors of advanced glycation end products increasing with the ageing process. Aim of the study was to assess the influence of glyceraldehyde and methylglyoxal on the mechanical properties of the LC and peripapillary sclera.

From 16 pairs of enucleated human eyes two stripes of 1 mm width were cut from each eye. One stripe contained the LC and the other the adjacent superior peripapillary sclera. The stripes of 8 eyes (one of each pair) were incubated in DMEM plus 0.5 M glyceraldehyde and of the other 8 eyes in DMEM plus 0.5 M methylglyoxal for 6 days. The other stripes of the eye pairs served as control and were placed in DMED for the same time. The stress strain relation was measured in the stress range of 0.02 - 6.0 MPa by a biomaterial tester with a prestress of 0.02 MPa and a velocity of 2mm/min. The distance between the clamps was 3 mm.

Stress values at 20% strain of the human LC were 1.97±1.48 MPa without glyceraldehyde, 3.40±1.60 MPa after incubation with glyceraldehyde (P=0.029), 2.42±2.22 MPa without methylglyoxal and 5.46±1.91 MPa (P=0.014) after incubation with methylglyoxal. The stress values of human peripapillary sclera without glyceraldehyde were 3.40±2.59 MPa, 7.45±4.46 MPa after incubation with glyceradlehyde (P =0.047), 4.80±3.05 MPa without methylglyoxal and 16.10±5.53 MPa (P=0.001)after incubation with methylglyoxal. At 20 % strain Young's moduli of the untreated LC are in the range of E=11.8-14.7 MPa and E=28.9-36.0 MPa of the untreated peripapillary sclera.

Glyceraldehyde and methylglyoxal increase the stiffness of the LC and of the peripapillary sclera in humans. These substances affect changes in the extracellular matrix according to the Maillard reaction as it occurs during the ageing process or diabetes.