I was watching the Chile Miners Rescue Operation on TV last night. One thing which i saw that all the miners who were rescued, were supposed to wear black glasses & the reason said was miners did not see the sunlight since two months therefore if after stepping on the surface, they see the sunlight with bare eyes then there eyesight could had been damaged which may even lead to blindness.

Can any body explain how the sunlight would have damaged their eyesight ? what effect the eyes had after not coming in direct contact with the sunlight in two months ?