an eye cap, this is from not shedding properly. You can do a search on leopard geckos and eye caps and read about. I had one that had this and I used terrimycin(sp.) in her eye for a few days and it cleared up itself.

Sometimes if this is the problem, it can become severe and cause eye damage if not taken care of. I would at least look into it.

Hope the gecko feels better soon
-----
Eve
Suncharmers Colorful Collareds & More