The forward will remain under the care of the Capitals medical team and have additional follow-up evaluations, the team announced Sunday.
Hagelin was injured when a stick struck his left eye during a battle drill near the end of practice Tuesday. He did not practice Wednesday.
"It's a serious eye injury," Capitals general manager Brian MacLellan said Wednesday. "I don't know that we know the full extent of it yet. He has a meeting here this afternoon with a different eye doctor. He had surgery on it last night, and it's to be determined what the next steps are here for him.
"The vision part is the biggest concern. We were really worried last night. I don't know, it's sort of positive news that the examination went in the right direction. But it's still to be determined on what the next steps are and what effect it'll have on him."
Hagelin has scored 14 points (three goals, 11 assists) in 53 games this season, his fourth with the Capitals.
"I think any time you have an eye injury, there's a concern," Capitals coach Peter Laviolette said. "First and foremost, there's a concern for him and just his well-being. It's unfortunate when something like that happens.
"And then secondly, with regard to our team, he's certainly a player that we're going to miss. He's counted on for a lot of different roles. That line has been excellent. I think he's one of the top penalty killers in the league. And so when you take a piece like that out of your lineup, you're going to feel it and somebody else is going to have to step up."
Hagelin has played the past two seasons regularly on the fourth line with Nic Dowd and Garnet Hathaway, and on the penalty kill.
"I think we've seen [players in Hagelin's] role," Laviolette said. "Conor Sheary's played it before. Brett Leason's played it before. [Axel Jonsson-Fjallby] maybe has taken some shifts on that line. So we have some options on how we want to go through it. We're going to get together and go through the lineup with regards to the game tomorrow and what our needs [are] on based on our personnel."
Hagelin leads Washington forwards in shorthanded ice time (100:25), and is second in shorthanded ice time per game (1:54) behind Dowd (2:01).
"Obviously he's a big part of our PK. He's our No. 1 PK guy," MacLellan said. "He's one of the better PKers in the league. That fourth line's been phenomenal for us over the last couple years and he's a big part of it. They play against top lines, they start in our own end and they do a good job, so we're going to miss him."
Joe Snively is out 4-6 weeks after surgery on his left wrist. The forward sustained the injury Feb. 28 against the Toronto Maple Leafs.
The rookie has scored seven points (four goals, three assists) in 12 games this season.
The Capitals (30-18-9) are fourth in the Metropolitan Division and have won two straight. They visit the Calgary Flames on Tuesday (9 p.m. ET; SNW, NBCSWA, ESPN+, NHL LIVE).
