The injury was discovered after Perreault started experiencing double vision, an issue that causes a person to see two images of the same thing, at which point doctors realized his retina had detached from its normal position.
The issue stemmed from a condition called lattice retinal degeneration, a thinning of the retina that happens over time which makes it easier for the retina to tear, break or, as in Perreault's case, lead to retinal detachment.
Perreault underwent a laser procedure to correct the issue in his right eye and will be re-evaluated in a couple of weeks.
Canadiens head coach Dominique Ducharme revealed that Perreault has been dealing with the injury for a while and did not sustain it in Saturday's loss to the Los Angeles Kings. There is no consensus on what causes lattice degeneration. It is not an inherited condition, but people with a family history are more likely to have it.
In Perreault's case, he was born with the issue and didn't know about it until something went wrong.
Perreault, 33, has played in eight games for the Canadiens this season, registering three goals and an assist thus far.