It depends on the cause of your heterochromia. If you are born with different eye colors or if your heterochromia is congenital, it will not affect your vision. The only difference between your eyes and eyes of normal people is that your two eyes are differently colored.
If your heterochromia is caused by diseases or trauma, whether yoru vision will be damaged is decided by the severity of your diseases or injury.
That isn't always the case people that gain heterochromia via injury or radiation from a toxic substance can have reduced or diminished vision. However people that are born with heterochromia are not at risk of losing eye sight. The reason being that genetic heterochromia does not effect the pupil. So the cones and rods are unaffected by the mutation. For example I have heterochromia in both eyes (aka double iris affect) and I have 20/10 vision. ALso heterochromia can in rare cases also effect the color of ones hair. These cases also have no effect on the person effected other than an abnormal color. In cases like mine people may have heterochromia in both eyes and their hair and still have no diminished properties. Finally it is normal for cases with heterochromia in multiple places to have a single mutant color throughout. In my case it is gold.
Well, in my opinion, it will not affect your vision, so you do not need to worry about it. Generally speaking, according to some experts, there is no permanent treatment for heterochromia. Sometimes the grey Colored iris picks up color as the child grows older. And of course, colored contact lenses are advised to treat it. But on the other hand, continued use of contact lens may lead to formation of follicles on the conjunctiva. And that can be dangerous too.
I am afraid it will. Although heterochromia can not be a trouble by its symptoms, its side effects like vision reduction can be really problematic, especially for those born with it. As we all know, our irises color is primarily determined by the concentration and distribution of melanin. There are various eyes colors due to our different parent-child combinations. As a result, heterochromia may be inherited, or caused by genetic mosaicism, injury or disease, as well some toxic chemical substances. Besides, heterochromia is always along with other eye conditions, which will lead to vision reduction. Further, as time goes by, our immuine system degrades worsing a minor eye illness, and then reduce the eye vision. We cannot cure the congenital heterochromia, but we can try to improve the situations of heterochromia resulting from injuries or diseases.