The injury was today described as "unusual and complex", and with Scotland departing for France in eight days' time it is clearly causing concern.
Callam, 24, sustained his problem during the World Cup warm-up loss to South Africa at Murrayfield on Saturday, forcing him to retire from the match.
He took a blow to the area immediately above his right eye - it was thought to have been an accidental clash of heads - and subsequently suffered blurring to his vision.
A visit to an ophthalmologist in Edinburgh was followed by further specialist consultation on Monday, and Callam remains under the supervision of the Scotland medical staff.
Team doctor James Robson said: "He has an unusual and complex injury to his face which is requiring us to take advice from several medical sources.
"We would hope to be in a position in the next 24 hours to confirm the extent of his injury and the prognosis for his recovery."