I think I misunderstood Creep0321. I was thinking he was advising a reduction of LORs from WOs down to 3-4. You are implying he meant the total number of LORs from 6 to 3-4?
I am also strongly considering PRK in the event my vision is deemed inadequate.
Yep, total number of LORs down to 3-4. You want quality, not quantity. Quantity can actually hurt you because the board members have ~2 minutes to look at your ENTIRE packet--in otherwords they might only glance at one or two or your LORs at random. So they better be rockstar ones. If you have 6 letters and two are totally badass, two are pretty good, and two are average, you risk them glancing at only the good or average ones. Put your best 3 forward and you guarantee they only see your best.
Now, you can OBTAIN as many LORs as you want. Pick the best three, and only SUBMIT those three (or four, if you're absolutely certain the quality of the four are equal).