Is it possible for a pet scan detect melanoma in the eye?

Sometimes: It is sometimes possible, depending on a few things - if the melanoma is large enough and if the malignant lesion is metabolically active. Pet scans work by detecting cells that take up more glucose and are more metabolically active than normal cells. Unfortunately, if the melanoma is small, the pet scan can't always pick it up (at least on today's pet scanners).

Yes: Yes although depends on the size of the tumor.