Mathematics of aging: Diseases of the posterior segment of the eye.

The changes caused by aging affect all body tissues. The vitreous humor, which fills the space between the lens and the retina, progressively liquefies and shrinks, eventually causing a posterior vitreous detachment. Retinal disorders caused by the breakdown of the blood retinal barrier are also associated with physiological aging. In this work a mathematical model of the pharmacokinetics of a drug eluted from an intravitreal biodegradable implant in an aging eye is presented. The influences of vitreous liquefaction and retina diseases are analyzed. The model is represented by a set of P.D.E’s describing the evolution of the concentration in a drug eluting implant, coupled with two systems of partial differential equations, describing the transport of drug in the vitreous chamber and the retina. Different scenarios of the physiology of vitreous and of inflammation’s degrees of the retina are numerically compared. The numerical results suggest a dominating influence of retina permeability.