It is true though that brown eyes are from a pragmatic evolutionary perspective the better adaptation, hence the reason why most of the population has them and not the random mutation for blue eyes.
Blue eyes only exist for sexual selection causes. Since the first mutation appeared it spread because people just found them pretty to look at, which they naturally are. They do not have any advantage, only problems.
Despite the fact that the total population worldwide of people with blue eyes is smaller than any other color, you have the most eye problems occuring in that demographic proportional statistically.