This is the page you need - http://www.aena.es/csee/Satellite?cid=1213017924001&pagename=subHome&Language=EN_GB&SMO=1&SiteName=Aeropuertos&Section=1&c=Page&MO=4
It states information about assisting persons with reduced mobility, including visually impaired. It looks like you need to request on your booking form that you need assistance during transfer. Madrid airport offer this service, so I would speak to the airline you are booked with about how you book this assistance. It should be part of your booking. :) Hope it helps.
I need someone to meet me from the plane and take me to another flight. I'm partially sighted and I only have an hour to get to my next flight so could be a bit tight!
Check out http://www.gomadrid.com/transport/airport_options.html. This might help you. There is a meet & greet service, but it's once you are through immigration. Is that what you mean?