George Charamba said Mugabe would "undergo a routine eye-check following a recent procedure".
The 90-year-old had cataract surgery on his left eye in February. He oftens travels to Singapore for medical treatment, following his EU travel ban in 2002.
Mugabe, in power since 1980, was re-elected in July in an election condemned by his main opponent former prime minister Morgan Tsvangirai as "a massive fraud."
His frequent visits to Singapore in recent years have led to growing speculation over the state of his health.
A US diplomatic cable from 2008, leaked in 2011 by anti-secrecy website WikiLeaks, quoted Mugabe's close ally and former central bank chief Gideon Gono as telling a former US ambassador the president had been diagnosed with prostate cancer.
But Charamba said Mugabe's only health concern was one of his eyes.