The benefits of tackling preventable blindness stretch beyond individual patients. The most common surgery taught by Orbis doctors is the removal of cataracts: the clouding of the eye’s lens. More than half of preventable blindness is caused by the ailment, yet it can be cured by surgical procedures costing from as little as $10.

Trachoma, an infectious disease that – left untreated – causes the eyelids to turn inward, costs as little as a few dollars to treat in its early stages. Treatment can help entire families break out of the cycle of poverty.

“These patients may have become an economic burden on their families and communities because they aren’t able to drive, work, read or write,” Walters explains. “These interventions are life-changing.”

Orbis’ model hinges on partnership – with its volunteers, with nonprofits, with governments, health ministries and local medical professionals. It has joined with the US-based Carter Center in a effort to eradicate trachoma worldwide – “something that is achievable in my lifetime,” says Walters; and, more recently, with the Qatar Fund for Development.

The joint venture, called Qatar Creating Vision, will provide up to 5.5 million eye screenings and treatments to children in India and Bangladesh, aided by partners such as the retail chain Specsavers and the nonprofit BRAC. It will also see the expansion of 19 paediatric eye centres in the two countries, and the creation of a specialist centre in Bangladesh to tackle eye ailments in premature babies.

Funding comes through cash from countries, governments and individual donors, and also as gifts in kind. The flying eye hospital was donated and fitted out by FedEx, while the pharmaceutical giant Pfizer has donated $18m-worth of antibiotics for use in the treatment of trachoma.

“We gain hugely in terms of fundraising and clinical delivery when we partner,” says Walters. “Where once we might have had great intentions but poor focus, now there is tight strategic thinking. Orbis is run like an efficient business, because we owe it to our donors to ensure our funding is efficiently spent in the field. At all times, we keep the philanthropic goal of what we’re trying to achieve top of mind.”