A person is deafblind if he or she has so impaired sight and hearing as to give him obvious difficulties in his daily life, according to the statutes of the Association of the Swedish Deafblind, FSDB.
This is a functional definition, not strictly based upon measurements of sight and hearing, but on how the person adjusts to his/her disabilities and on his/her needs. It also acknowledges the fact that deafblindness is a double disability, giving greater difficulties than just adding the problems of visual to those of auditory impairment.