Question: Why doesn’t a person go blind after taking 500 big steps?
A. The Mishna Berura (301:1:1) Says , based on a pasuk, “And he shall honor it from what he does on your ways” refers to the fact that the way you walk on Shabbos should not be the way you walk during the week, for it is the way of people to rush and run to their business. And even during the week one shouldn’t take big steps because it takes 1/500th away of one’s eyesight. It just that on Shabbos there is also a prohibition dating back from the times of the prophets.
B. Tosfos in Taanis 10b “p’sia” says that only the first step will take away eyesight because it’s only 1/500 each big step.
Answer: Either you can say he gets used to taking big steps so the eyes adjust or every beginning if something is harsh but after continuing then each steps gets weaker and weaker and only takes 1/500 of the previous 1/500th that was lost.