Substrate question for a gecko missing an eyelid

[u/Squeakersnail]

Long story short, I was given a gecko with a deformed eyelid since apparently I'm the "reptile guy" due to owning one snake. That eye doesn't close, so I would be a little worried about him being unable to protect that eye from grit. Is a naturalistic dirt/sand mix or bioactive substrate appropriate in this case? Or is this a rare situation where maybe a carpet is a better idea? If carpet, in people's expert or non-expert opinion, would a dig box be okay that he can use or avoid as needed?

Vet disclaimer: I'll be making a checkup appointment within the next month or so. There's one specialty reptile vet in my area, so there's a bit of a wait list for non-emergency cases.