Straining the eggs will remove the outermost liquid part of the egg white, which is what causes an excessive amount of wispy egg whites. The photos below show a comparison of the amount of liquid egg white in a fresh egg (Figure 1) versus an older egg (Figure 2). The fresh egg white is distinct in shape, which will result in a perfectly shaped poached egg once it has been strained. I recommend using fresh eggs for this recipe as they will hold their shape much better.