Alex Zanardi's eyesight is at risk as a result of the hand cycling crash that has left him in a coma with serious facial and head injuries.
Giuseppe Olivieri, the neurosurgeon who operated on the former F1 driver turned paralympian, announced on Tuesday that the 53-year-old Italian will remain in a coma for a further 10-15 days.
"We don't know how much of the coma is due to the drugs and how much is due to the neurological conditions," he told Italy's Sky Sport 24.
Olivieri praised the doctor who initially worked on Zanardi after he swerved onto the wrong side of the road during a race and collided with a truck.
"The greatest merit belongs to the anaesthesiologist who intubated him correctly," said Olivieri. "It was difficult to do it in the middle of the street with a patient in that condition."
An update provided by the Santa Maria alle Scotte hospital in Siena, Italy, said on Tuesday that the "neurological picture remains unchanged in its severity".
"The patient remains sedated, intubated and mechanically ventilated."
There is speculation that the serious facial injuries suffered by the former Williams driver could cost him his eyesight.
"The former Formula 1 driver is at risk of losing both eyes," said the Swiss newspaper Blick. The same information was carried by the German news agency SID.