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E. Spoerl, K.–G. Schmidt, H. Bergert, S. Kersting, H. Saeger, A. Boehm, L. Pillunat; Biomechanical Properties of Lamina Cribrosa and Peripapillary Sclera in Diabetic Rats . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1226.
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© ARVO (1962-2015); The Authors (2016-present)
Diabetes mellitus is considered a risk factor for primary open angle glaucoma (POAG). The biomechanical changes of the tissues of the optic nerve head and the adjacent peripapillary sclera (PPSC) were investigated in diabetic rats.
Diabetes mellitus (blood glucose ≥ 300 mg/dl, 3 independent measurements) was induced in 20 Wistar rats using streptozotocine (i.v., 70 mg/kg body weight). 25 matched non–diabetic rats were used as controls. After 12 weeks the rats were killed, the eyes enucleated and processed immediately. The eyes were cut 360° at the equator and the lens, retina and choroidea were removed and 2 strips (width: 1 mm) of each eye were prepared containing lamina cribrosa (LC) or PPSC. The stress–strain relation was measured in the stress range of 0.02 – 6 megapascal (MPa) using a biomaterial tester applying a prestress of 0.02 MPa and a strain rate of 2mm/min, clamp distance was 2 mm.
LC and PPSC were stiffer in eyes of diabetic rats when compared to controls. At 15 % strain difference the stress of the LC of diabetic rats (7.93±2.58 MPa) was statistically significant (P= 0.0004) increased when compared to the normal LC (5.18±1.71 MPa). The stress of the diabetic PPSC (3.81±1.33 MPa) was increased when compared to normal PPSC (3.24±1.69 MPa), but did not reach statistical significance (P=0.218). The calculated Young’s (elastic) modulus at 15% strain was is 30.9 MPa for the normal LC and 42.8 MPa for the diabetic LC . The Young’s modulus was 19.7 MPa for the normal PPSC and 27.2 MPa for the diabetic PPSC.
This is the first study showing increased stiffness of LC and PPSC in diabetic rats. These results might be explained by collagen cross–linking by advanced glycation endproducts in the optic nerve head due to the higher level of glucose in diabetic rats. An increase of tissue stiffness might lead to an increased mechanical stress and therefore affect retinal ganglion cell and astrocyte metabolism.
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