I don't know anyone that is sight impaired, but as the stoker on our tandem I'd said that the stoker needs to be very comfortable with the abilities of the captain. My captain isn't the best at communicating with me (too much talking - but he's an excellent captain & I have total faith & trust in his biking abilities), so I have to go by the feel of the bike to know he's changed gears, braking, turning, etc. It does become very intuititive (feel the bike). He'll tell me when he wants more power & if he wants me to clip out (I don't stay on the back at stops, etc. - we both clip out on the right & start up together). The stoker can only see side to side (forward you're only seeing the back of the captain) so it's the captain's responsibility to watch out for, and respond to, any hazards. I don't think riding with a sight impaired stoker will be much different than riding with one that isn't. As long as you're comfortable captaining the tandem & you do practice rides before the event so you're comfortable with each other's style, you should be just fine.