This exact thing happened to me. It happened and I knew something was wrong as soon as I rolled over after the massage. I kept blinking and it was very milky and unclear. I saw an opthalmologist ASAP and it was a PVD. I'm very nearsighted and the pressure they put on the back of my head caused PVD in the right eye. I could tell something had happened. There are articles out there where this has happened before. It was not a random coincidence.
Im only 31! I have pain where my neck meets shoulder and just used my home massaging device then had black floaters in my vision. Most doctors are undereducated quacks, who only got into the business bc at the time if felt like the job that would provide the most money.
The PVD and floaters are much more likely due to being 51 than the massage. The only way that might be a factor if the eyes were massaged heavily thru the closed lids.
JCH MD