The Spaniard suffered a concussion after a spectacular crash in Mandalika on Sunday, when his Honda cartwheeled end-over-end as it disintegrated, before he landed heavily on his left arm and smacked his helmet on the ground.
Marquez also suffered from diplopia, or double vision, at the end of last season.
“It seems that I am experiencing deja vu,” he wrote on Twitter. “During the trip back to Spain, I began to have discomfort with my vision.
“We decided to visit Dr. Sanchez Dalmau, who confirmed that I have a new episode of diplopia.
“Fortunately, it is less severe than the injury I had at the end of last year. But now it’s time to rest and wait to see how the injury evolves.”
Marquez had to be airlifted to hospital after his crash at the weekend, although he did walk away from his ruined Honda.
The next race is in Argentina on April 3, with Marquez now a serious doubt.
Honda said he would undergo further medical tests before deciding how long he will need to recover.
The 29-year-old has struggled with a series of injuries in recent seasons.
He missed almost the entirety of the 2020 campaign after breaking his right arm in the season-opening race.
Marquez also sat out the first two Grands Prix last year before struggling to recapture his best form when he returned.
However, he did win back-to-back races before the initial bout of diplopia forced him to miss the last two dates on the 2021 schedule.