Harry, sorry about your sister.
I too have Retinitis Pigmentosa.....diagnosed in 1989. At first this is devastating news, but like anything else, you learn to live with it. Although there's still no treatment or cure, research has come a long way since then. I do take the daily dose of 15,000IU Vitamin A which is believed to slow the progression of this disease. I suggest a visit
http://www.blindness.org/ for some more info on RP