No abstract

The aqueous humor (AH) flow in the anterior chamber (AC) due to saccadic movements is investigated in this research. The continuity, Navier-Stokes and energy equations in 3D and unsteady forms are solved numerically and the saccadic motion was modeled by the dynamic mesh technique. Firstly, the numerical model was validated for the saccadic movement of a spherical cavity with analytic solutions and experimental data where excellent agreement was observed. Then, two types of periodic and realistic saccadic motions of the AC are simulated, whereby the flow field is computed for various saccade amplitudes and the results are reported for different times. The results show that the acting shear stress on the corneal endothelial cells from AH due to saccadic movements is much higher than that due to normal AH flow by buoyancy induced due to temperature gradient. This shear stress is higher on the central region of the cornea. The results also depict that eye saccade imposes a 3D complicated flow field in the AC consist of various vortex structures. Finally, the enchantment of heat transfer in the AC by AH mixing as a result of saccadic motion is investigated.

In this study, the distributions of intravitreal injected drugs in post-vitrectomy human eyes, which are subjected to periodic saccade movements, are investigated. The computational model for the vitreous cavity of human eye is a sphere with one side truncated by the eye lens. A dynamic mesh technique was used to model the eye motion and the unsteady 3-D forms of continuity; Navier-Stokes and concentration transport of drug equations were solved numerically. The numerical model was validated earlier for the vitreous liquid flow field. The predicted drug concentration for idealized geometry was compared with the available analytic solution and excellent agreement was observed. The validated computer model was then used to simulate a real vitreous cavity filled with Balanced Salt Solution or aqueous humor as a vitreous substitute in order to obtain distribution of drugs in the post-vitrectomy eyes or liquefied vitreous. Additionally, effects of locations of drug injection, drug diffusion coefficients and saccade amplitude on the drug distribution and its uniformity were investigated. Although the earlier findings in the literature reported a day or a week as a needed time for drug uniform distribution in the vitreous substitutes, the present work depicts that saccade movements augment the transport of the drug in a way that the uniformity of the drug distribution can be achieved in a matter of minutes. Furthermore, in a vitreous cavity subjected to the saccade movements, the diffusion coefficient of drugs does not significantly affect their distribution after a few minutes. Even the injection location does not matter as uniform distribution is achieved after some time.

In the present research, the motion of the nano-drug in the vitreous chamber of human eye due to saccadic movements in post-vitrectomy eyes is investigated. The average radius of the vitreous cavity in human eye is equal to 12 mm. This cavity is filled with a liquid in post-vitrectomy eyes. A dynamic mesh technique was performed to model the eye motion. The unsteady 3-D forms of continuity, Navier-Stokes and concentrations of nano-drug equations were solved numerically. The numerical model was validated comparing the results of the flow field with available analytic solutions and experimental data for a sphere as an ideal model of vitreous chamber which a very close agreement was achieved. Then, the numerical simulation was performed to a real model of vitreous cavity filled with BSS (Balanced salt solution). The convection and diffusion of nano-drug in the filling fluids of post-vitrectomy eyes is computed and the results are compared with the diffusion of the nano-drug in the stagnant vitreous. The comparison depicts that the saccade movements of human eye accelerate the drug motion one to two orders of magnitude higher than that due to diffusion in stagnant vitreous chamber.