Reneggaide my experience is limited on this. We had a buff orpington pullet that I am not sure if she was born blind or if it came about later on, but we noticed around 5 months of age she was always moving different from the others, and when we moved them to the main coop for winter boarding she took a bit to figure out where everything was. My daughter raises these girls of course so once she figured out this girl must be blind she was already very attached.
This hen lived here for 2 years, we would have to teach her where the food and water was if we moved it, but once she had it figured out she was good. She layed on the floor but produced well, we never bred any eggs from her (she stayed in our laying flock) just in case it was genetic, but she had a good full life. We sold her to another family last year and they report she adjusted well and still is going strong.
So the need to cull if they are doing ok, finding food and water, I dont think is necessary. BUT it will be a bird that will need constant supervision to make sure that it does know where food and water is, and limit the amount of time you move it to a new pen to minimize stress on it.