In that case, I'll leave the place holder for spells and go on.
Saves: Base save bonuses are Fort +1/3 HD, Ref +1/3 HD, and Will +1/2 HD + 2.
Abilities: A gem eye's Dexterity increases by +2, it has no Constitution score, and its Intelligence changes to 3.
Skills: Recalculate the gem eye's skill ranks based on its new HD and Int.
Feats: A gem eye keeps the feats of the base creature and gains one, usually Improved Initiative.
Environment: Any, usually same as base creature.
Organization: Any.
Since these are Intelligent, I decided to leave Wis and Cha unchanged, but we could peg them to 10 and 12 or something if you want.