Majority of high functioning DB actually. Most of those who are classified as "DB" actually have it as a part of a more profound/ severe multihandicapped disorder. (ie multihandicapped as in "kid on the developmental level of a baby/toddler, mentally cannot walk and talk) There are a lot of higher functioning DB people, and as you said Usher's is the majority of the high functioning ones. Although I remember a REALLY old user, Lady Duke who was DB due to other things......Yes, Usher is majority portion of deafblind population. I have 90 degrees with both eyes and great acuity with contact lenses.
Interesting, does could progress into full blindness in later life? Do you have to take steroid medicine everyday?