The influence of the IOP on the geometrical and biomechanical properties of the linear model of the eye globe - effect of the optical self-adjustment.

The deformations of the cornea due to the variation in IOP (observed in humans) change its dioptric power and its distance to the retina to such a degree, that acuity of vision should be affected. In order to find the eyeball's mechanism of compensation (self-adjustment) for optical disturbances caused by the changes in IOP a specific biomechanical model of eyeball with a limbus ring is proposed. The computational models were set up using Finite Elements Method. We tested: different approximations of the cornea's surfaces, different values of Young's moduli of the cornea (Ec) and the sclera (Es), an equivalent tensile stiffness of the limbus ring. The limbus ring limits deformations of the cornea due to variations in IOP. So far the biomechanical models of the eyeball without limbus ring have excluded the self-adjustment effect. Each of the investigated parameters of the model affects the self-adjustment ability. The stiffness value (required for self-adjustment) of the lmbus ring is maximal at a ratio Es/Ec=5. Our numerical results have shown that the value Es/Ec=5 is in close relation with the self-adjustment effect of the eye and confirmed the biological investigations.