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VH Barocas, JJ Heys; Free Convection In Aqueous Humor And The Krukenberg Spindle: Theoretical Analysis . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3285.
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Purpose: To assess whether free convection in the aqueous humor could be a feasible explanation for the characteristic spindle-shaped pigment deposits (Krukenberg spindle) on the posterior cornea in some pigment dispersion syndrome patients. Methods: A three-dimensional steady-state static-eye computer simulation of flow and heat transport in the aqueous humor was developed. The iris and lens were assumed to be at a uniform 37°C temperature, and the anterior cornea surface was assumed to be at a uniform 34°C temperature. Heat transport across the cornea was assumed to be entirely by passive conduction. Once a flow field had been determined, simulated pigment granules were then released from various locations on the pupil margin and tracked. Location of the tracks was recorded, as was the distribution of particle locations (i.e., how much time was spent in different locations). Results: The temperature gradient across the anterior chamber creates a sufficient density gradient to drive a recirculating flow that rises along the anterior iris/lens and descends along the posterior cornea. This recirculation causes a slight skewing of the temperature profile within the anterior chamber but only a small change in the rate of heat transfer from the iris to the cornea. Particle tracks showed a pronounced vertical component, and particle position distributions tended to be vertical ellipses. Conclusion: Free convection within the anterior chamber is physically reasonable and is consistent with the characteristic shape of the Krukenberg spindle. Other motions of the eye, including saccades, miosis, and accommodation, would need to be considered in a detailed analysis of the flow, but spindle generation appears to be capturable by a simple model.
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