It said there had been problems with accommodating requests efficiently and a lack of materials in Braille.

“U.S.C.I.S. has policies in place to ensure accommodations are provided for people with disabilities when requested and we make every effort to ensure that these policies are followed at all times,” the agency said in a statement on Friday. “If U.S.C.I.S. becomes aware of an error in adhering to these policies, we make every effort to ensure corrections are made.”

The agency said it would provide Braille English tests for any blind or visually impaired citizenship applicant who requested them.

Many people who are blind do not use Braille, in part because new technologies have given them different ways to access text, said Mary Rosenberg, a lawyer with Access Living, a Chicago nonprofit that promotes disability rights.

“But yeah, it’s definitely a problem that people who need it, and who request Braille in various government forums, don’t receive it,” she said.

Mr. Delgado, who has been blind since birth, came to the United States when he was 16. He said he left his home in the Mexican state of Guerrero because he wanted better educational opportunities, and because his family feared the growing influence of drug cartels in his home city, Iguala.

Mr. Delgado and his relatives, who now have green cards, live in Pembroke Township, Ill., a rural area about 70 miles south of Chicago that is one of the poorest places in the state.