Contribution of saccadic motion to intravitreal drug transport: theoretical analysis.
OBJECTIVE
The vitreous humor liquefies with age and readily sloshes during eye motion. The objective was to develop a computational model to determine the effect of sloshing on intravitreal drug transport for transscleral and intra-vitreal drug sources at various locations


METHODS
A finite element model based on a telescopic implicit envelope tracking scheme was developed to model drug dispersion. Flow velocities due to saccadic oscillations were solved for and were used to simulate drug dispersion.


RESULTS
Saccades induced a three-dimensional flow field that indicates intense drug dispersion in the vitreous. Model results showed that the time scale for transport decreased for the sloshing vitreous when compared to static vitreous. Macular concentrations for the sloshing vitreous were found be much higher than that for the static vitreous. For low viscosities the position of the intravitreal source did not have a big impact on drug distribution.


CONCLUSIONS
Model results show that care should be taken when extrapolating animal data, which are mostly done on intact vitreous, to old patients whose vitreous might be a liquid. The decrease in drug transport time scales and changes in localized concentrations should be considered when deciding on treatment modalities and dosing strategies.
Department of Mechanical Engineering, University of Minnesota, Minneapolis, Minnesota, USA.
Ram K
RK
Balachandran
Victor H
VH
Barocas
D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism*; D001692:Biological Transport; D003198:Computer Simulation; D006801:Humans; D008268:Macular Degeneration / Q000188:drug therapy; D008954:Models, Biological; D010599:Pharmacokinetics; D012438:Saccades; D014822:Vitreous Body / Q000378:metabolism*
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