Hello, Im new here and have 2 dwarf sand geckos (stenodactylus) that live in a 10 gallon. Ive had them about a year.
Today I noticed my bigger one Gumby has something seriously wrong with one of his eyes

It is swollen to twice the size, and is glassy/milky. Im pretty sure it was not like this yesterday. I noticed it when I gave them their crickets today.
He was laying on his basking rock and didnt even flinch when I put the crickets in which is not normal for him. I put him down near a cricket and he chased it a bit, then lost interest as if he couldnt see them properly to grab, and went back to his rock. He also looks like he is going to shed soon, not sure if that could have anything to do with it.
Does anyone know what could have caused this, or if there is anything I can do to help him. He has always been a very happy active guy and now he looks miserable and Im afraid he might die

He was full grown when I got him so I have no idea how old he is.