Have added this page due to having known about 2 Megaesophagus dogs who were also blind and they were diagnosed with Sudden Acquired Retinal Degeneration Syndrome (SARDS).
http://www.pethealthnetwork.com/dog-health/dog-diseases-conditions-a-z/sudden-acquired-retinal-degeneration-syndrome-sards-dogs

A specialist in Iowa (Iowa State University) is doing some pretty amazing work with dogs diagnosed with SARDS or a related condition.

A great book that is entitled “Living with Blind Dogs”  https://petcarebooks.com/books/living-blind-dogs/

https://www.petplace.com/article/dogs/pet-health/blindness-in-dogs/

Physical affects:
Can be caused by SARDS (Suddenly Acquired Retinal Degeneration Syndrome) and PRA (Progressive Retinal Athrophy)
Blind dogs see with their hearts
Sense of smell becomes even stronger and they suddenly get into things they never thought of before
Become bored more easily so a little extra entertainment may need to be provided
Dogs use the senses of hearing and smell more than sight and although one losing its vision suddenly may have more adjustment issues and some depression