I also thought that was insulting with the wheel chair icon. A person in a wheel chair has problems walking, not (necessarily) their vision. How about "Help" in text?...less confusion and possible anger
There are symbols for visual impairment, but they're not international.
(http://commons.wikimedia.org/wiki/File:Pictograms-nps-access...)
(http://3.bp.blogspot.com/-HfEx4Y_O_Gs/Tf0huVPZBXI/AAAAAAAAAC...)