Why did Creslin lose his sight permanently, while Dorrin only lost his sight for a short period of time?

Creslin did not lose his sight permanently, but was blind often in much of his later life. The reason was that, in effect, Creslin was an indealistic extremist, while Dorrin was an indealistic moderate, who was much more aware of the need for the Balance and for maintaining it. Creslin literally remolded the climate of a large chunk of the world, and then used order to create a great deal of chaos on top of that.