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Semira Kaya, Kurt Knogler, Guenther Weigert, Stefan Sacu, Gerhard Garhofer, Leopold Schmetterer; Estimation of Ocular Rigidity in Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5674.
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Theoretical models have proposed that increased structural stiffness of the sclera may play a role in the pathophysiology of age-related macular degeneration (AMD). There are, however, only few data available that demonstrate such biomechanical alterations in vivo. In this study, the hypothesis that patients with AMD show an abnormal ocular structural stiffness was tested.
44 patients with AMD and 22 healthy control subjects matched for age, sex, intraocular pressure and systemic blood pressure were included. The ocular pulse amplitude (PA) and pulsatile ocular blood flow were assessed using pneumotonometry. Ocular fundus pulsation amplitude (FPA) was measured by the means of laser interferometry. As a measure for structural stiffness, a coefficient of ocular rigidity (E1) based on the Friedenwald equation was calculated relating PA/FPA.
There was no difference in systemic blood pressure and intraocular pressure between groups. FPA (AMD: 3.3 ± 1.2µm; controls: 3.9 ± 0.8µm; p = 0.025), but not PA was lower in the patients with AMD than in the control subjects (AMD 2.8 ± 0.6mmHg; controls: 3.0 ± 1.0mmHg; p = 0.34). E1 was significantly higher in the patients with AMD (0.91 ± 0.11AU) than in the control subjects (0.70 ± 0.07AU; p < 0.001).
The present study indicates increased scleral rigidity in patients with AMD. This supports the concepts that the biomechanical properties of ocular tissues are altered in the disease. Whether this is causatively involved in the disease process or a consequence remains to be shown in longitudinal studies.
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