IN 1984 JORDAN KASSALOW, an optometry student in Boston, volunteered to treat hundreds of patients in rural Mexico. Many had struggled to find work because of their poor eyesight but couldn't afford corrective lenses. Of the 70% who needed eyeglasses, Kassalow figured half could get by with the sort of ready-made models sold in drugstores. "Why don't we train local people to sell reading glasses?" he thought.
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