| Popis: |
Numerical calculations of the aqueous humor dynamics in the anterior chamber of both the rabbit and the human eye are presented to delineate the basic flow and transport mechanisms. The calculations are based on a geometrical model of the eye, which represents the Trabecular mesh (TM) as a multi-layered porous zone of specified pore sizes and void fraction. Buoyancy is observed to be the dominant driving mechanism for the convective motion in both orientations (horizontal and vertical) of the eye. Reducing the TM pore size does not appear to have a significant influence on the intra-ocular pressure (IOP) until the pore size drops below 1 micron beyond which a significant increase in IOP is observed. Simulations of particle transport are also performed to gain insight about the movement and deposition of particles of different characteristics and to identify the mechanisms for the development of observed pathological structures. Simulations predict the formation of Krukenberg Spindle through pigment cell deposition on the corneal surface. Simulation of heavy particles present in the AH show that they gravitate inside the eye and a layered structure is formed at the bottom of the anterior chamber. The simulated particle deposition patterns are seen to correspond with clinical observations. The development of elevated pressure in the eye with pupillary block is simulated and analyzed. Potential surgical procedures (iridectomy) are simulated through virtual opening of holes at different positions along the iris disk. The effect of the location of holes along the iris surface is analyzed for single and two hole iridectomy. Key issues considered in analyzing the results are (a) reduction in IOP, (b) the asymmetry introduced in the flow profile, (c) adequate circulation of the flow in the different region since the flow provides the nutrition to the tissues and (d) the particle deposition on the ocular tissues. It is observed that when a single hole is created, the 12 oclock iridectomy provides better results than the other locations. The preferred arrangement with the two-hole iridectomy is the 9 oclock and 3 oclock positions since the flow distribution is most symmetrical and circulation is the strongest. |
