MRI AND QUANTITATION OF OCULAR CIRCULATION

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The principal objective of this proposal is to apply magnetic resonance (MR) imaging to the quantitation of fluid (water) movement in the anterior chamber of the living rabbit eye. We use a novel approach using topically applied GdDTPA and H217O, T1 and T2 contrast agents, respectively, as the tracers. Spin-echo MR imaging will be performed using a 1.5 Tesla imager in conjunction with small (2-5 inch diameter) radio-frequency surface coils. Fast imaging techniques also will be adopted (when available) which permit the collection of more data points and reduction of motion artifacts. MR imaging technique enables us, for the first time, to visualize and quantify the flow of water including aqueous outflow, iris circulation, and water diffusion in the eye. There are no comparable clinical techniques now in existence. The specific aims are: (1) to refine methods for the study of ocular fluid flow using topical GdDTPA and H217O; (2) to quantify the fluid flow in the anterior chamber; and (3) to test the effects of three anti- glaucoma agents, pilocarpine (a miotic), acetazolamide (a carbonic anhydrase inhibitor), and timolol (a non-specific beta-blocker) on the kinetics of the fluid flow. We expect to accomplish the following: (1) documentation of aqueous/water flow dynamics; (2) evaluation of the fluid flow altered by anti-glaucoma agents; and (3) development of novel MRI diagnostic techniques for the evaluation of the fluid flow. The results of these studies will further our understanding of the aqueous/water flow dynamics. The diagnostic techniques will permit us to evaluate changes in the fluid flow in primary open-angle glaucoma, nanophthalmos, narrow-angle glaucoma, neovascular glaucoma, and their malignant forms, and aid eventually in the management of these diseases.