MOSCOW: A top Russian doctor said Monday that the Bolshoi ballet's artistic director would regain sight in at least one of his eyes following a brutal acid attack that his coworkers blamed on infighting at the great theatre.

"The trend is generally positive," the Moscow health service's chief eyesight specialist Larisa Mashetova said in televised remarks.

"He is regaining sight faster in one eye, but I think that we are going to even things out for both," said Mashetova.

"Still, the recovery process will take a lot of time."

Forty-two-year old Filin -- an acclaimed dancer who was appointed artistic director in 2011 -- suffered third-degree burns to his face when a masked man cornered him near his house in central Moscow.

Preliminary findings released Sunday showed the assailant used sulphuric acid.

Several of the theatre's greatest dancers have since reported infighting at the Bolshoi and voiced fears that the attack may be linked to Filin's decision to award top roles to specific dancers.

They said that Filin himself had on occasion mentioned feeling like he was in a constant fight with some of his staff.

Moscow police have so far made no arrests while spending the weekend interviewing Bolshoi dancers and directors as part of their investigation.

Filin underwent emergency surgery on Friday and is scheduled for another procedure on his skin Tuesday.

Doctors said that another operation on his eyes has tentatively been scheduled for Wednesday.

Mashetova said Filin is in a good frame of mind.

"He is a person with a sense of humour. He has a positive attitude... and that helps the recovery," said Mashetova.

"He feels well. But it is still too early to make any forecasts."