Eye damage can occur with any contact lens, including circle lenses. Circle lenses are supposed to be cosmetic, and they have less water content than normal contact lenses. It’s not recommended to use circle lenses for more than five hours, which is why circle lenses could be more damaging than other lenses.
That said, if the contact lens doesn’t fit (if you didn’t make sure the lens shape actually fits your eye), that can make your eyes hurt and your eyesight become fuzzy. And that goes for both circle lenses and contact lenses. In addition, you might have gotten a defective lens. There are many possibilities, but in my opinion, if you are extremely careful with all lenses, (meaning taking care of your lenses, tossing them at the first sign of discomfort, wearing them for the correct amount of time, getting your eyes checked regularly to see if your contact prescription has changed, and so much more) the chances of damage to your eyes can be decreased a lot. My motto: My eyes are important, proceed with caution with anything that goes in or around my eye and be super-ultra attentive.
Edit: A disclaimer for all circle lens posts - I am not an eye doctor. My advice is just that, advice from experience and what I’ve read. If anyone has problems with any lens ever, please go see an eye doctor. Also, everyone’s eyes are different. Cannot stress this enough, if you think or feel there is something wrong, stop using whatever you are using and go see an optometrist.