What it is: An international charity that runs a fully self-sustained flying eye hospital built into a converted DC-10 passenger plane.
What it does: Operates on thousands of people in developing countries each year, training local medical professionals on the plane and through outreach programmes in local hospitals, making five or six training visits a year. So far 70,000 practitioners have been trained.
How it's funded: £3m in public donations and corporate sponsorship, National Lottery funding and gifts in kind, including plane fuel, parts and maintenance, surgical technology and equipment, staff accommodation and travel.
The operating room in the Orbis flying eye hospital is situated over the wings and fitted with six cameras that project images to the lecture theatre in what was the first-class section.
Up to 48 doctors can view the surgery and question the procedure throughout via a microphone worn by the surgeon.
"Surgery takes twice as long because I explain everything I am doing for the doctors watching on the video screen," says Dr Carlos Golarte.
"If we go in and do 100 cataract operations and leave the skills behind, that's great. But we often carry more equipment than we need on board so we can leave behind the technology the people we train need as well.
They have to be able to operate themselves after we leave," he says.
Before the surgery can take place, the patients must be screened and assessed. The most commonly occurring diseases are trachoma, cataracts and glaucoma. Golarte says: "We have about 100 patients on screening day, and many more turn up hoping to be seen. We screen everyone, regardless of whether they are invited, and the doctors prepare medical notes and select the best teaching cases to operate on the next day."
Joao Pedroso, healthcare technology trainer and biomedical engineer, says: "It's a long day for everyone on board. It's non-stop - sometimes our days start at seven and don't finish until nine." He is often away with Orbis for four months at a time. "But I am busier at home planning projects with the offices and hospital partnerships abroad," he says.
Dr David Paton, an ophthalmologist from Houston, Texas, was so horrified at the scale of curable blindness in the developing world that he put the technology and skills required to treat eye disease into a converted DC-8 plane, which departed for the first mission in Panama City in 1982.
In 1994 it was replaced by the larger DC-10.
"We are the only one in the world," he says. "Heads of state have come aboard to show their support, and they are provoked into making big changes in their countries." On Orbis's recent visit to New Delhi, India, the Prime Minister was so impressed with what he saw that he ordered a satellite video link-up to an operation, held in the plane, which was beamed to lecture theatres in the three biggest eye-care institutions in India in order to reach and train as many eye specialists as possible.
The pilot, Captain Gil Chase, also helps to set up the hospital and screen patients. "Officially, the flight crew's job ends when the plane lands, but there's so much to do just to set the place up." Are the long hours worth it? Pauline Dabydeen, a nurse from Glasgow, says: "The most emotional time is post-operation when the patient can see. They are so grateful, but we are just doing our jobs. We haven't done anything out of the ordinary."