Are the Other Witchers Mutated?

The Witcher: Enhanced Edition

Meanwhile every other witcher we encounter in the series has the proper eyes. Or maybe Witchers vary from school to school, Geralt is known to have undergone extra mutations, so maybe the cat eyes aren't common for Kaer Morhen witchers, but are typical of other schools.

Is Geralt different than other Witchers?

Geralt is a result of his exposure to further mutation, due to his unique tolerance for the Trial of Grasses; this extended process left his hair devoid of pigment and possibly left him even stronger and faster than his brethren. How this process was developed is a mystery even to the Witchers themselves.

Are all Witchers mutated?

Probably not. Witchers are once-normal humans who got mutated by a combination of medieval science and magic, which made them superhuman (more Captain America than Superman) and able to take potions too toxic for normal people.