This is somewhat of a controversial topic as it new, expensive and a lot of unsubstantiated claims get made for it. Fungal infections of the toenails (or onychomycosis) is a common problem. It causes the nails to become deformed and grow with a yellowish discoloration. The biggest issue in this problem is that treatment can takes months as you need to wait until the fungal elements grow out with the nail as it grows. During that time, especially in the damp and moist environment of the shoe, the nail can easily get infected again as the fungus just love that dark and moist environment in the shoe. So, whichever treatment is used, no matter how good it is can easily fail due to the reinfection. The use of the laser has become popular in recent years with lots of anecdotes but no hard science to support it. The FDA have approved it as safe, but have not tested how effective it is. There are plenty of other treatments that have been shown to work. More research is needed to know how the laser treatment stacks up to the other treatments.
Famous Words of Inspiration...
"You play the hand you're dealt. I think the game's worthwhile."