According to the American Mathematical Society, most blind mathematicians work in geometry, which is considered to be the most visual math discipline. The inability to see might actually be an advantage to blind mathematicians in this discipline, because they are not locked into a perception-based view of the world and can more easily picture objects in more dimensions than fully sighted people.
More facts about blind mathematicians:
Besides geometry, blind mathematicians also make up a significant portion of topologists, or those who study the properties of shapes that continually change form, like a Möbius strip or homeomorphisms. This also is an extremely visual discipline.
Some of the most famous mathematicians in history were blind, including Leonhard Euler, who produced about 850 works in his life — about half of which after he went totally blind. Euler was most famous for his contributions to graph theory and for revolutionizing mathematical notation. Other famous blind mathematicians include Nicholas Saunderson and Lev Semenovich Pontryagin.
Blind mathematicians often work very differently from fully sighted mathematicians. Fully sighted mathematicians work by writing down proofs or drawing images on paper, but blind mathematicians tend to do most of their work in their heads and often have a more intuitive understanding of shapes.