Bicycling Blind is an organization that connects tandem-owning folk (captains) with the visually impaired (stokers).
Here’s a testimonial from Rob B. in Austin, TX, from their site:
Since launching my profile on the US Blind Tandem Cycling Connection, I have met two competent pilots. One, I have ridden with in three different states and on three different tandems! We have also become great friends. This site is an excellent resource! Thank you!