The 19-year old Jamaican will spend the remainder of the season with the O’s after a short loan spell with Coventry City earlier this season.
Loza, who joins Tottenham’s Shaquile Coulthirst and Stoke City’s Jamie Ness at Matchroom Stadium, will provide good depth for Orient according to manager Russell Slade.
"With a small squad, young players like Shaquile and Jamar will give us some much-needed depth,” he told the club’s official website.
"In the meantime our priority remains to bring in a goalkeeper and more senior forward."
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