Hi,
To avoid problems like that with the pillowcase use cheap ones with a low thread count. Soak it and then seal the top and push down to see if air can pass through it if you are unsure.
You really do need to keep the eye moisturised with artificial tears or it will definately dry out and get infected - unlike us snakes cannot blink to spread moisture over the eye surface.
That's why a course of antibiotics is also generally recommended.
But, as everyone already covered, this is why we are always very reluctant to help people remove eyecaps in any situation where anything might go wrong and why we never say tape is a good idea. :(
dr del