My Husband Went Through Vetrectomy Eye Surgery For Retina Detachment

My husband went through Vetrectomy Eye surgery for retina detachment 4 weeks ago. After two weeks, the gas bubble was absorbed. His vision was clear , it wasn't dark at all. But now all of sudden, he started to see a little bubble and a shadow in his eye.
Is this normal or do you think he should book an appointment again with his doctor?