The vast majority of global health problems do not consist so much of finding a cure as delivering one. Improving health in the world's poorest countries requires solutions that are cheap and simple to administer -- and the good news is that these are increasingly available. For example, changing the standard response to diarrhea from saline drips (which require sterile needles and medical staff) to sugar-salt solutions (which require neither) has saved millions of lives that would otherwise have been lost to diseases such as cholera.
Next up may be the scourge of poor sight. There are lots of people who can't read signs, watch TV, or recognize a face across the room without corrective vision. I'm one of the lucky few among them who can afford to do something about it; I have four optometrists within blocks of my office and enough money to buy glasses. But around the world, millions of people who should be able to see clearly are almost blind for lack of corrective treatment. The World Health Organization (WHO) estimates that about 150 million people worldwide who need glasses do not have them. In sub-Saharan Africa, only about 5 percent of people with poor eyesight have glasses. Skilled eye professionals are also extremely rare; Rwanda, a country of 10 million people -- an estimated 1.2 million of whom need eyeglasses -- has just 12 optometrists and ophthalmologists.
On top of eye conditions that can be fixed with glasses, over 20 million people worldwide can't see because of cataracts. Cataract operations are not complex, but they do require a surgeon and a properly equipped hospital. And costs for even a straightforward cataract surgery in the United States range above $3,000 -- or more than 50 times per capita annual health expenditure in Pakistan, for example.
This lack of access exacts a heavy toll on the world's poor. A randomized trial in China suggests that giving glasses to children can have an impact on their performance at school equivalent to an extra half-year in class, which should come as no surprise to any kid who has squinted at the blackboard from the back row of the classroom. Children with poor vision in northeast Brazil are 10 percent more likely to drop out of school and nearly 18 percent more likely to repeat a grade. The WHO estimates the global cost of poor eyesight at $269 billion a year in lost productivity.