By Michael Voss
BBC News, Havana
Hundreds of eye patients are treated every day by Cuban medical staff
The waiting room at Cuba's largest eye hospital, Pando Ferrer, is packed with patients.
Many come from across Latin America and the Caribbean, with everything paid for by the Cuban government.
Basil Ward is from Barbados and is in Havana to have a cataract removed for free.
"I could have had the operation in Barbados but I would have had to wait a year, there's a huge waiting list there," he says.
Others do not even have that choice; health facilities are almost non-existent or unaffordable in many of the poorest parts of the region.
Pando Ferrer Hospital carries out a range of eye operations
Mr Ward is here under a programme called Operacion Milagro or Operation Miracle.
Launched five years ago, it has already helped restore sight to more than 1.6 million people.
Operation Miracle came out of an adult literacy programme which the Cubans were running in Venezuela.
They discovered that a lot of people could not read or write because they were unable to see properly.
"Fidel Castro always considered health a major priority so he asked us to devise a simple fast operation, a sort of miracle to restore people's sight," said Dr Marcelino Rio, director of the Pando Ferrer hospital and head of Operation Miracle.
The Cubans have turned mass production eye operations into a fine art. Pando Ferrer Hospital alone can perform 300 operations a day.
Treatments range from cataracts and glaucoma to corneal transplants.
Most of the equipment is European and Asian; US companies cannot sell to Cuba because of the trade embargo.
314 million people visually impaired worldwide
Of these 45 million are blind
Around 85% of visually impaired people live in developing countries
Cataracts are leading cause of blindness
About 85% of cases avoidable
Corrective eye wear could give normal vision to more than 12 million children
Source: World Health Organization
There are similar facilities throughout the island as well as dozens of eye surgery centres which the Cubans have opened across the Americas and parts of Africa.
Operation Miracle is just one part of an extensive international medical assistance programme, which some have dubbed Cuba's "medical diplomacy".
In the 1960s and 1970s, Cuban leader Fidel Castro tried to export revolution through armed struggle.
Che Guevara died attempting to lead an abortive guerrilla campaign in Bolivia. Tens of thousands of Cuban troops were sent to fight in the anti-colonial wars in Africa.
But medical assistance was always part of the package. The first medical mission was sent to Algeria in 1963 during its war of independence. Large numbers of doctors also went with the troops to Angola.
In recent years this medical aid has grown significantly, becoming a central part of Cuba's international relations.
Cuba trains overseas medical students, sends tens of thousands of doctors abroad and has rapid response disaster assistance teams. These were sent to both China and Pakistan after their devastating earthquakes.
According to the Cuban authorities, there are 24,000 students from developing countries studying health care on the island. This includes 10,000 medical students enrolled at the prestigious Latin American Medical School (ELAM).
All receive full scholarships on the condition that, when qualified, they return home to work.
There are no figures available for what Cuba spends on its international medical programmes but it must account for a large part of this cash-strapped island's budget.
Medical aid has become a "service export". Venezuela provides subsidised oil in return for the around 20,000 Cuban medical staff working there.
Resources are stretched in Cuba, itself a poor country
But probably the biggest benefit for Cuba is that such medical diplomacy has helped boost its image throughout the world and paid dividends politically.
While Washington is still considering whether to end Communist Cuba's isolation and start direct negotiations, every other country in the Americas has ties with the Cuban government, now led by Fidel's brother, Raul.
Honduras, a traditional US ally in the region, now has Cuban doctors working in some of the remotest and most vulnerable areas where there are no hospitals. At the same time there are more than 1,000 Honduran medical students being trained in Cuba.
"If offering a helping hand is an extension of foreign policy, then (it is) welcome. I wish other countries would do the same," Honduran Foreign Minister Patricia Rodas told the BBC during a recent meeting of the Non-Aligned Movement in Havana.
There is a similar arrangement in Belize, the former British colony in Central America.
"We used to have a bad image of Cuba but that has changed. Cuba is not the monster it seemed to be," said Said Badi Guerra, Belize's Ambassador to Cuba.
"Our medical students would never be able to complete university because of the cost, yet they come to Cuba for free. We are very grateful for it."
For Cubans, the health assistance programmes offer the opportunity to travel and earn some hard currency as well as helping others.
Physiotherapist Mabel Juiz volunteered to join the large Cuban medical team that went to Pakistan after the 2005 earthquake.
Cuba's medical system: Impressive but under pressure
She spent six months living in a tent in the mountains and was able to save enough to furnish her apartment back home.
"I wanted to be useful and help others. It was really sad seeing so much destruction," she said but added that she would gladly volunteer for any future missions.
There are signs, though, that committing so many resources to helping others is having an impact on the health service back home, particularly in longer waiting times to see family doctors.
Last year the government announced a major shake-up, closing many smaller one-doctor surgeries and replacing them with larger polyclinics.
Cuba's free health service continues to boast impressive infant mortality and life expectancy rates, but with limited resources the system is under pressure.
There are shortages of medical supplies and equipment and many of the facilities are in desperate need of repair.
Some Cubans resent the money spent on foreigners. Most though appear proud of their achievements and the impact this Caribbean island is having on the health and sight of others.