* Former PM says eye problems prevent attendance at trial
* Three doctors, including top eye specialist, make checks
* Berlusconi charged with paying for sex with minor
* "Ruby" trial was meant to start on Monday
MILAN, March 11 (Reuters) - Italian judges ordered checks to be made on former prime minister Silvio Berlusconi on Monday to verify his claim that health problems meant he was unable to attend his trial on charges of paying for sex with a minor.
The 76-year-old media billionaire, who faces a series of court hearings in separate trials this month, has been in hospital since Friday because of an eye problem that he says has forced him to cancel a number of public appointments.
However prosecutors believe that his stay in hospital, which falls in the middle of a political crisis caused by last month's inconclusive elections, may only be a delaying tactic. On Saturday judges rejected his argument that he was unable to attend a trial for tax fraud.
Berlusconi denies any wrongdoing in the case, in which he is charged with paying for sex with former nightclub dancer Karima El Mahroug, better known under her stage name "Ruby the Heartstealer", when she was under the legal minimum age of 18.
He says he has been subject to politically motivated "judicial persecution" by what he says are left-wing judges who want to end his political career.
The hearing in the Ruby trial had been expected to be held on Monday with a final ruling in the case on March 18.
Three doctors, including a cardiologist and a senior eye specialist were charged with conducting the inspection at the San Raffaele hospital in Milan. Results were expected on Monday.
The checks adds to an increasingly bitter political battle around Berlusconi as political parties struggle to deal with the aftermath of February's election which left none of them able to form a government.
Berlusconi's centre-right alliance holds the second-biggest bloc in parliament but appears to be shut out of government by the hostility of both the centre-left Democratic Party and the anti-establishment 5-Star Movement of former comic Beppe Grillo.
Separately, the court also rejected a request by Berlusconi's two main lawyers for the trial to be delayed because they had to attend a meeting of his People of Freedom party, which they both represent in parliament.