No, some people with heterochromia are born with different eye colors of their two eyes. But they see perfectly. Their vision is not defected. There is nothing wrong with their eyes expect for the colors. However, if heterochromia is not congenital and is acquired from diseases or trauma, the answer depends on the situation of his diseases or trauma.
Heterochromia refers to a difference in coloration, usually of the iris but also of hair or skin. It is hard to cause blindness but changing the color of your iris. Heterochromia can let the color of your eyes light subtly day by day. Sometimes it is also possible to lead to cat eyes.
Yes, it is really bad for you to suffer heterochromia. Your eyes will have two different colors. However it has little possibility for you to get blindness because of it. You should just protect the eyes from the healthy diet and good rest. You should eat more food with vitamin C to moisture the eyes. The good rest is also needed. You should not use the computer for a long time.