the cornea is the transparent outer layer of the human eye. because it must be transparent to light, it does not normally contain blood vessels. therefore, it must receive its nutrients via diffusion. oxygen from the surrounding air diffuses to the cornea through the surface tears whereas other nutrients diffuse to the cornea from the inner parts of the eye, such as the vitreous humor and lens.during operation, the cornea produces waste in the form of co2gas that must be expelled to keep the eye healthy and functioning. this is accomplished by the simultaneous diffusion of co2from the cornea to the surrounding atmosphere, which generally features a low co2concentration.it is therefore critical that modern contact lens materials allow sufficient diffusion rates of oxygen and carbon dioxide. without oxygen, the cornea will warp, lose transparency, and become susceptible to scarring. the body may also react by growing additional blood vessels into the eye, which can damage the cornea.if an decrease steady-state flow rate of o2(oxygen molecules per second) to the cornea is desired, which of the following contact lens / ambient condition modifications is not likely to be useful?