This is where problems start. Is it really gazing or is it an entirely separate neurologic issue? Is it congenital rather than inherited? I have a feeling that any sort of neurologic issue in a snake has a very very good chance of presenting as stargazing. Trauma, ingestion of toxins, tumors, rabies, encephalitis of various causes, spinal cord issues can cause odd motor movements in animals. Remove the toxins and rabies from snakes, and that's still a large list of things to consider.
When do we truly call it gazing, and when do we call it a neurologic deficit?