A new rating system, ImpactMatters aims to rank the world's most cost-effective nonprofits. The ranking, based on how much good a nonprofit achieves per dollar of cost, is broken into a variety of categories, including health, veterans, clean water, poverty, hunger, education, climate change and homelessness. Five vision charities took top 10 spots in the Health category, with Sightsavers clocking in as the number one health charity, Sankara Nethralaya Om Trust at number six, Benevolent Missions International at number seven, Vision Outreach International at number nine and World Cataract Foundation at number ten. Take a look at the list here, and learn more about how these nonprofits are making a world of difference.