I have introduced Big Red my 3 year old crown tail. I have never mentioned Big Red is also blind. I acquired him from a friend that was moving a year and a half ago. He was a Walmart rescue and was partially blind when she got him. In the past 3 months he has got totally blind. He knows his tank well enough now but when clean extra care must be taken as not change his tanks configuration. I have the bottom of his tank laid out with different color gravel to indicate where each piece of decor goes.
The biggest challenge with a blind Betta is feeding. He can not see my finger well enough to take food anymore so we has to switch to using tweezers to make sure his food makes it to his mouth. He is the only fish I have ever owned that I recommend tapping on his tank. It does not frighten him and we do it to let him know we are there. He will follow the tank wall around till he bumps into a finger. Then wait open mouthed till he feels the tip of the tweezers on his lip and bits down. I invested in an expensive pair of surgical stainless steel tweezers 6 months ago when I noticed he seem to be having more trouble finding the tank sides.
Big Red is still going strong though and I hope to have him with me for another 2+ years