Some ants ARE blind, but most are not.
Some ant species are blind, especially those that are subterranean, but not all. Many ant species have compound eyes, which they use to hunt for food. Some species have ocelli, three simple eyes, which detect light. Most ants have marginal eyesight relying on other senses to help assist in foraging for food, but some have excellent eyesight, such as the Myrmecia species, commonly referred to as bull ants.
Blind Ant Species
Army Ants: This group is not a single species of ants, but encompasses more than 200 species across 18 genera and 6 subfamilies. An ant is classified as an army ant due to its aggressive swarming predatory behaviors. These ants do not have compound eyes, and cannot see, instead using their antennae and pheromones to smell, touch, and communicate.
Martialis heureka: This unknown ant species was discovered in a Brazilian rainforest in 2003. One of the most primitive species discovered yet, this ant is pale in color and eyeless. When its founder exhibited the ant to an expert at Harvard University's Museum of Comparative Zoology he exclaimed that that ant species may as well be from Mars it is so different. The species was thus named Martialis heureka, which essentially translates to "From Mars! Wow!"