Ever look closely at a chameleon's eyes? They look like shower heads that move around independently of each other It's safe to say they can watch anything coming and going without making the slightest movement but for their eyes. It looks weird.
It is assumed to be a possible genetic deformity, but as far as I know no specific gene or mode of inheritance has been identified. I think that the possibility of a vitamin A deficiency in the mother is another potential cause worth investigating because it has been linked to eye deformities in many other animals.