In this very rare case stem cells helped this patient save his vision. In most intrinsic eye diseases and mutations stem cells would not help restore, improve or save someones vision. The limbal stem cells main purpose is only to regenerate the top layer of the cornea called the epithelium. A healthy limbus that produces that proper amount of stem cells can completely regenerate the epithelium in as little as 14 days. Most corneal dystrophies occur in the layers under the epithelium in the stroma and endothelium.
I am not against stem cell research as there are a lot of areas where they could and are doing good but this particular case is not the strongest argument of curing widespread eye disease with the use of stem cells.