Thanks for the link, shorthorsemom. I will read this later when I have time. I love the appaloosa coat colors, but would like to know much more about the vision issues.
The 2005-06 study on Night Blindness by Sandmeyer et al revealed that CSNB is associated with Appaloosa coat patterning of a specific type. Appaloosas with coat patterns indicating they are homozygous for LP (fewspots & snowcaps) are affected. Appaloosas that are heterozygous for LP are not affected by CSNB (blanketed, leopards, etc.) Horses that are true solid non-characteristic Appaloosas, with no dominant copies of LP, are not affected by CSNB either.
As an appaloosa breeder, I've had horses with night blindness, and found that simply leaving on the barn light or an outside light if the horse was left outside, was all it took to keep them happy. The light needs to be bright enough to read a book by, and should provide light to see their water and feed. Generally, in the nighttime, the nightblind horses didn't move from the circle of light, and were happiest in the barn under lights at night -- especially any snowcap or fewspot mare with a foal.
One of my snowcap mommas was really panicky at night, and once she foaled, she couldn't find her foal in the dark, so she was gratefully stalled every night with her young foal. Once baby was strong and followed momma's directions, she was happy to be outside with her baby as long as the barn light was on. She'd let baby wander outside the light, but one call from momma was all it took to have baby racing back to her.
These horses require no more real "care" then the others, as long as you allow for them not being able to see in the dark -- so your pasture must be safe for them. They tend to shy from shadows, and may not want to enter dark trailers -- so you just accomodate them by turning the trailer so the inside is lit by the sun. Other than being aware of the inability to see in the shadows/nighttime, you won't notice much difference in caring for them.
One mare I had, the prior owners never knew she was nightblind. She'd managed for years without anyone making accomodations for her. I discovered it when someone left the gate open to one of the pastures, and all the horses went out to the lawn except her -- she was standing still in the middle of the pasture looking around and quite panicked at not "feeling" the presence of her friends. After that, a light was put up the next day -- and all was well.
To me, making accomodations for this condition is just part of being an appaloosa breeder.
Remember, many horses become adapted to their condition, since it is present at birth, and does not change over time.