We perform a novel 3D study to quantify the corneal oxygen consumption and diffusion in each part of the cornea with different contact lens materials. The oxygen profile is calculated as a function of oxygen tension at the cornea-tear interface and the oxygen transmissibility of the lens, with values used in previous studies. We aim to determine the influence of a detailed geometry of the cornea in their modeling compared to previous low dimensional models used in the literature. To this end, a 3-D study based on an axisymmetric volume element analysis model was applied to different contact lenses currently on the market. We have obtained that the model provides a valuable tool for understanding the flux and cornea oxygen profiles through the epithelium, stroma, and endothelium. The most important results are related to the dependence of the oxygen flux through the cornea-lens system on the contact lens thickness and geometry. Both parameters play an important role in the corneal flux and oxygen tension distribution.The decline in oxygen consumption experienced by the cornea takes place just inside the epithelium, where the oxygen tension falls to between 95 and 16 mmHg under open eye conditions, and 30 to 0.3 mmHg under closed eye conditions, depending on the contact lens worn. This helps to understand the physiological response of the corneal tissue under conditions of daily and overnight contact lens wear, and the importance of detailed geometry of the cornea in the modeling of diffusion for oxygen and other species.
3-D model, corneal oxygen distribution, corneal oxygen flux, Monod kinetics model, oxygen tension, soft contact lens
| INTRODUCTIONThe subject of the oxygen demand of a human cornea has received a great deal of attention in recent years, and has been the subject of an extensive debate, with many models appearing, aiming to explain the distribution of oxygen consumption, the profile of partial pressure of oxygen, and the flux though the entire cornea (epithelium, stroma and endothelium).Most models carry out their study assuming a 1D geometry for the oxygen transport through the cornea/tear/lens system. 1-6 Some of the models assume a constant thickness and oxygen consumption, and they have evolved considering different multilayers for the cornea/tear/lens system as a mono-dimensional model. 3,4,[7][8][9][10] However, the first models considered a constant corneal oxygen consumption rate in which the diffusion equation was treated only as steady, and not as time-dependent. 5,[11][12][13][14][15] Negative values of the partial pressure