Pinworms are what I was thinking, but them seem a bit too elongated/thin.My guess would be pinworm eggs but I would have someone who knows more than I do about reptile parasites give a professional opinion to be sure
I picked up a book about parasitism in reptiles recently and they have quite a few pictures of pinworm ova. They seem to vary fairly widely from species to species so maybe this is what the ones that live in iguanas look like and its different from other species??