I work in theatre, and more specifically, Inclusive theatre, which means I work with a lot of people who are physically and/or mentally disabled. I find it impossible to believe that their hadicapes are a result of past Karma, and some people I have spoken to would be extremely offended by this. If fact I know of many people in high places who have lost jobs due to thinking in this way. Also it's worth mentioning that people I know who have Autism, cerebral palsy, downs syndrome, seem perfectly content, despite their "Limitations".
"The original heart/mind shines like pure, clear water with the sweetest taste. But if the heart is pure, is our practice over? No, we must not cling even to this purity. We must go beyond all duality, all concepts, all bad, all good, all pure, all impure. We must go beyond self and nonself, beyond birth and death. When we see with the eye of wisdom, we know that the true Buddha is timeless, unborn, unrelated to any body, any history, any image. Buddha is the ground of all being, the realization of the truth of the unmoving mind.” Ajahn Chah