The 73-year-old Italian prime minister is facing a second night in hospital after doctors admitted his injuries were worse than they had thought.
Mr Berlusconi also suffered a broken nose and lost two teeth during the assault as he signed autographs at the end of a stormy political rally in Milan yesterday.
He spent a quiet, if painful, night in hospital last night and is having trouble eating, his personal doctor said today.
He is also suffering from a severe headache.
However his friends are rallying around him - a spokesman said French President Nicolas Sarkozy and Russian President Vladimir Putin have both already phoned to commiserate with Mr Berlusconi.
His doctor, Alberto Zangrillo, said the premier's injuries would take at least 15 days to heal.
Berlusconi, a popular but divisive figure, said 'I'm fine, I'm fine' as he arrived at the hospital yesterday.
He reportedly asked to be brought newspapers upon waking up, no doubt wanting to read coverage of the assault on the front pages.
Berlusconi was attacked when a man stepped from the crowd, dodging bodyguards, before smashing the politician in the face - apparently while clutching a model of the city's Duomo cathedral in his clenched fist.
The prime minister told an Italian TV presenter visiting him in hospital that he considered it ‘miraculous’ not to have lost an eye in the attack.
‘This is truly a bad day for Italy, and it's the duty of all the political forces to ensure that Italy does not go back to the years of violence,’ Gianfranco Fini, Berlusconi's top conservative ally, said.
The incident triggered an outpouring of solidarity for Berlusconi from allies and critics, just as the prime minister seeks to regain political momentum after a bruising year battling mounting legal troubles and sex scandals.
Allies blamed the assault on an atmosphere of hatred swirling around the billionaire businessman.
‘What they've done to Berlusconi is an act of terrorism,’ Umberto Bossi, head of the far-right Northern League and a close Berlusconi ally, said.
‘An oppressive climate has been felt for some time and what's happened today is a worrying sign.’
The attacker, named last night as Massimo Tartaglia, was arrested by police and taken away.
Just hours after the attack, Facebook groups had sprung up hailing or attacking Tartaglia, including one fan site with more than 32,000 fans that labelled him a man with "lots of courage".
Television footage showed a stunned Mr Berlusconi with blood around his mouth as he was lifted to his feet by aides.
He was bundled into his official car but immediately got out, apparently in an effort to show he was not badly injured. After looking out into the crowd, the aides pulled him back into the vehicle.
As police officers swamped the rally, Mr Berlusconi was driven to a nearby hospital where he was given a CAT scan.
Doctors said that as he was being treated on a stretcher, he had told them: 'I'm fine, I'm fine, don't worry about me.'
There was no immediate suggestion of a motive for the attack. Police sources said that 42-year-old Tartaglia, from Milan, was not known as a political activist and had no criminal convictions apart from minor driving offences.
They added, however, that he had been 'receiving medical attention for mental problems' for ten years.
Before the attack, Mr Berlusconi had delivered a fiery speech to supporters of his People of Freedom party in the square in front of the cathedral. Scores of opponents had also gathered to try to drown out his speech.
Defence minister Ignazio La Russa who witnessed the attack said: 'I saw blood coming from the premier's nose and mouth. He was then pushed into the car by his bodyguards and driven away.'He was actually trying to step on the edge of the door so that he could stand and wave to the crowds but his bodyguards would not let him do it, they pushed him inside.
The attacker was held immediately by the police and it's a good job he was because he risked being lynched by the crowd. There would have been just pieces of him left.'
The attack came after a speech that had been billed as politically significant but revealed no big policy shift.
Berlusconi launched a familiar tirade against the left and rattled off a list of government achievements, in a characteristically feisty performance aimed at shoring up his standing and ratings.
It is the second time that Mr Berlusconi has been attacked in public. In 2004 he was hit over the head with a camera tripod while strolling in Rome.
Last night's incident came despite reports in November security had been tightened-around him following fears that he was being targeted by Left-wing terrorists.
Mr Berlusconi has been at the centre of controversy for much of the year. In April it emerged that he had attended the 18th birthday party of a lingerie model, giving her a £5,400 gold and diamond necklace.
It prompted his long-suffering wife Veronica Lario, 53, to announce she was divorcing him because she could no longer be with a man who ' associated with minors and was ill'.
In June it emerged that escort girls had been among women invited to parties at his official residences. One claimed to have slept with him.
He has also been at the centre of a political storm after an immunity law his government introduced was overturned, meaning he could be put on trail for corruption.
In recent weeks there have been claims he was in the Mafia, allegations he has dismissed as lies.
An opinion poll published on Saturday indicated his popularity had fallen four percentage points to just over 50 percent as Italians fretted that his legal entanglements could distract him from government duties.