Are there people with epicanthal folds in eyes, but not mentally challenged?

Yes: Epicanthal folds occur commonly in developmentally normal infants and children. They are also common in those of Asian descent as well as certain native peoples. The vast majority of those with epicentral folds are of normal (or perhaps well above average intelligence). A few rare developmental disorders exhibit mental delay in the context of epicentral folds.

Epicanthal Fold OK: An epicanthal fold refers to skin fold from your upper eyelid that covers part of the inside corner of your eye. It is most common in asians. And not related to mental ability.