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A. B. Hommer, G. Fuchsjäger-Mayrl, H. Resch, C. Vass, G. Garhofer, L. Schmetterer; Estimation of Ocular Rigidity Based on Pneumotonometric Measurement of Pulse Amplitude and Laser Interferometric Measurement of Fundus Pulse in Patients With Primary Open Angle Glaucoma. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4597.
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There is evidence from theoretical models and animal studies that the biomechanical properties of the optic nerve head and the sclera may play a role in the pathophysiology of glaucoma. There are, however, only few data available which demonstrate such biomechanical alterations in vivo. We tested the hypothesis that patients with primary open angle glaucoma have an abnormal ratio of ocular intraocular pressure amplitude and ocular fundus pulsation amplitude indicative for altered scleral rigidity.
Seventy patients with primary open angle glaucoma (POAG) and 70 healthy control subjects matched for age, gender, intraocular pressure and systemic blood pressure were included in this trial. The ocular pulse amplitude (PA) and pulsatile ocular blood flow were assessed with penumotonometry. The fundus pulsation amplitude (FPA) was measured using laser interferometry. The ratio between PA and FPA was taken as a measure of the ocular rigidity (E1=PA/FPA).
All ocular hemodynamic parameters were lower in POAG patients than in healthy control subjects. In addition, a significant positive correlation was found between FPA and PA in both study groups (correlation coefficients between 0.88 and 0.90). The factor E1 was significantly higher in patients with POAG (0.77 ± 0.11 mmHg/µm) than in healthy control subjects (0.73 ± 0.08 mmHg/µm, p = 0.013).
The present study indicates increased compliance of the sclera in patients with POAG. This is compatible with a number of previous animal experiments and supports the concepts that the biomechanical properties of ocular tissues play a role in the disease process.
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