It is true that smoking, drinking, drugs, as well as other harmful things would definitely lead or at least contribute to macular degeneration. And macular degeneration is quite a complicated disease which could make lots of troubles for your eyes. Therefore, it would be wise for you to quit those bad habits and improve your health by getting exercise and a better diet.
Yes, what your mom says is right. Smoking could cause your yellowing of the eyes because of the damage on the liver. When you find that the color of the eyes is changed, you should take great notice. You may have the problems at the whole body. You need to take the medical care to treat it. You should not smoke too much. Or else, it will be so bad for your health.