Hi Ellen, I've heard of a couple of people (Marrow Forums Members) who suffered with this condition. I think in their case(s) it was due to prolonged use of Steroids.
You might want to visit Laura's or Grant's CB pages as they both recently have dealt with a similar or perhaps the same condition you are describing. I believe Grant had a hip replacement, but I'm not sure if Laura did.
www.caringbridge.org/visit/laurajevans or
www.caringbridge.org/visit/grantbeltrami
(Wendy his mom moderates his sight)
I hope this helps.