Can you get eye problems like proptosis 4 years after being treated as a thyroid patient?

Not common, but yes.: Graves' disease is caused by abnormal antibodies made by immune cells that target some of your own tissues. Even though the thyroid hormone levels are normal after treatment, the antibodies may still be there, and can affect the eyes afterwards, although this doesn't happen often. Some people can get eye problems, and only later become hyperthyroid.

Eye problem: Yes. It's called "exophthalmos ". This is caused by antibodies inflaming the eye lining. These antibodies are the same ones which caused thyroid dysfunction before leading to treatment. See an ophthalmologist.