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E. Spoerl, V. Zubaty, A. G. Boehm, L. E. Pillunat; Estrogen Improves Distensibility of the Lamina Cribrosa. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3299.
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The aim of the study was to investigate the influence of estrogen on the distensibility of the lamina cribrosa (LC). If an increased stress in the LC due to elevated IOP can not be reduced by deformation this might be a risk factor for the development of glaucoma.
From 24 porcine eyes the posterior part of the sclera including the lamina cribrosa were used. Twelve samples were incubated in culture medium enriched with 10 µM estradiol for 7 days. A group of 12 porcine corneas incubated in culture medium without estradiol for the same time served as control. Strips of 1 mm width were cut from the posterior sclera through the lamina cribrosa. The stress strain relation was measured by a biomaterial tester. The Young’s modulus and the distensibility were calculated.
The stress-strain curves show a lower stiffness of the estrogen treated LC. At 10 % strain the stress was 849±384 10³ N/m² in the control group and 455±253 10³ N/m² in the estrogen group. This difference was statistically significant (P=0.01). The Young’s modulus was 22.84 MPa in the control group and 10.79 MPa in the estrogen group. The distensibility as the reciprocal of the Young’s modulus was increased by 110 %.
Estrogen increases the distensibility of the LC. In this case a reduction of the stress by deformation is facilitated. Through this mechanism estrogen might protect the axons for elevated stress in the LC. This biomechanical effect of estrogen was already proven for other tissues like cartilage, skin, cornea, and blood vessels.
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