Grant: Collaborative Health Research Projects (NSERC partnered)

CONTEXT: The pathogenesis of open angle glaucoma is poorly understood. While intraocular pressure (IOP) is confirmed as a major factor, ocular blood flow and the elasticity of the sclera and lamina cribrosa may play a role. We propose a new theory uniting these three factors. We propose that the lamina cribrosa moves backwards with each cardiac cycle, driven by the pulsatility of the choroid, while the retina moves in the opposite direction. These counter-directional movements could lead to stretch damage of axons that form the optic nerve, which run from the retinal nerve fibre layer through the lamina cribrosa. This hypothesis is based on our recent studies, which suggest that the biomechanical compliance of the lamina cribrosa differs dramatically between patients at risk of aggressive glaucoma and patients with stable glaucoma [Lesk et al., Arch Ophthalmol, 124, 1568 (2006)], as well as on recent literature on the pulsatile movements of the retina. To test this hypothesis, we have developed a prototype of a novel non-invasive device based on Low Coherence Interferometry (LCI), which measures with high spatial (400 nm) and temporal resolution (0.01 sec) the movement of intraocular tissues, such as the retinal inner limiting layer and the lamina cribrosa [Singh et al Exp Eye Res (April 14, 2010)]. This device has recently been successfully tested on human volunteers. OBJECTIVE: The objectives of this project are (A) to evaluate our theory on actual glaucoma patients at Hôpital Maisonneuve-Rosemont (HMR) using the developed non-invasive device; (B) to improve the prototype device for better data acquisition and stability; (C) to develop image analysis protocols that permit the efficient and reliable extraction of meaningful data; (D) to develop a complementary system with greater lateral resolution on the platform of a commercially availible device. CONCLUSION: This project could lead to the first method to ascertain whether a patient with early glaucoma is at high risk for rapid loss of vision, and thus requires early aggressive therapy.Ultimately, improved understanding on the pathophysiology of glaucoma could lead to new therapeutic modalities.