Poro-elastic and poro-visco-elastic models describe fluid flow through porous, deformable media. They are relevant in many applications in bioengineering and medicine, such as tissue perfusion and fluid flow inside cartilages and bones. In this talk, I will discuss the application of these models specifically to optical perfusion and its relation to glaucoma, as well as confined compression tests for biological tissues. In both these applications, and many other biological applications, pressure loads on the tissue (represented in the model through boundary traction) play an extremely important role. We will investigate the effect of these pressure loads through a sensitivity analysis of the system with respect to the boundary traction. Our results, paired with certain theoretical findings on the existence and regularity of solutions, suggest a novel hypothesis on the causes of damage in biological tissue.