its only common in the super lessers, im not sure how common it is, I've seen quite a few super lessers and never seen a bug eye one in real life. Quite a few pictures online though.
As there are a lot of super lessers that do not have bug eyes, it is probably not a simple genetic condition. IMHO, the genetics predispose a super lesser, but an environmental factor triggers the development of the condition. Identifying the environmental trigger is the hard part, of course.