Yes, they can. Besides blindness, there can be allergic reactions. Some people are allergic to the filler substances, which can cause swelling, redness, and pain. Also, there can be uneven distribution of the filler, leading to an unnatural look. True stories tell of people having to deal with these issues for weeks or even months.
Sure. There are other serious problems that under eye fillers can cause. Infection is one of them. If the injection is not done in a sterile environment, bacteria can enter the injection site and cause an infection. This can lead to more swelling, fever, and in severe cases, it may require hospitalization. Another problem is that over time, the filler may migrate to other areas, causing lumps or an asymmetrical appearance. There are many real - life cases of these problems.