The 29-year old Bosnian-born Swiss gloveman joined the League One O's earlier this month and was due to stay at the Matchroom Stadium until February 8.
Orient boss Russell Slade was grateful for the efforts of the former Grasshopper custodian who kept three clean sheets in four outings in the third tier.
"We'd like to thank Eldin for all his efforts here over the last few games and he's done a fantastic job," Slade said.
"It's unfortunate for us but the process of finding a replacement has already started."
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