Zimbabwe's President Robert Mugabe is not asleep when he closes his eyes for long periods during meetings but is resting his eyes, his spokesman says.
"The president cannot suffer bright lights," George Charamba was quoted as saying by the state-run Herald newspaper.
The president is currently receiving specialised medical treatment for his eyes in Singapore.
Mr Mugabe, 93, intends to stand in presidential elections next year.
"I feel like a failure when there is this reading that the president is sleeping in conferences - no," Mr Charamba said.
He then compared Mr Mugabe to the anti-apartheid icon Nelson Mandela, whose eyes were sensitive to flash photography following years of working in a limestone quarry while imprisoned on Robben Island.
President Mugabe's foreign trips are often criticised in Zimbabwe, where healthcare has declined in recent years and medical professionals say they are poorly paid.