Six American scientists credited with advances in eyesight research and clinical care are sharing a €1 million ($1.3 million) prize from a Portuguese foundation.

James G. Fujimoto, David Huang, Carmen A. Puliafito, Joel S. Schuman, Eric A. Swanson and David R. Williams on Friday won the Lisbon-based Champalimaud Foundation's annual Vision Award. They are all based in the U.S.

The award, established in 2007, claims to be the largest monetary prize for work on eyesight and one of the world's largest scientific prizes.

The foundation said the winners have developed groundbreaking techniques for visualizing retinas and have uncovered important details about the structure of eyes.

It said their findings are vital for the diagnosis and treatment of blinding diseases and research into visual functions.