The lawyer for the first officer of the Costa Concordia says the captain was not wearing his glasses the night the ship sank and asked the first officer to check the radar for him.
The cruise liner capsized off the island of Giglio on 13 January, after hitting a rock, killing at least 25 people. Seven people are still unaccounted for.
Prosecutors in Italy accuse Captain Francesco Schettino, 51, of causing the disaster by bringing the ship too close to the shore.
The captain has acknowledged that he brought the ship too close to the shore, but says he was not the only one to blame for the tragedy.
Lawyer Salvatore Catalano was speaking outside a pre-trial hearing in the town of Grosseto on Saturday.
A theatre has been turned into a temporary courtroom. Relatives of the victims, survivors and lawyers attended.
The BBC reports no journalists or members of the public were allowed to attend.
Evidence and testimony amassed since the crash, including recordings from the ship's black box, was handed over to a panel - made up of two naval experts and two academics.
First officer Ciro Ambrosio is also under investigation. An Italian newspaper, Il Fatto Quotidiano, has published a leak of an account he is said to have given to the inquiry.
He said Captain Schettino had explicitly taken sole command of the ship on the approach to the island.
At the last moment, he realised he was too close and ordered a sharp turn away but it was too late and the ship hit the rocks.
According to the newspaper, the first officer said Captain Schettino was reluctant to acknowledge the gravity of the crisis and was not truthful when the Coastguard began demanding information.
Seven other officers and the company are also under investigation.