Complete blindness does not occur in Retinitis pigmentosa. This is one positive thing. Those affected first experience night blindness, followed by constriction of the visual field and eventually the loss of central vision late in the course of the disease.
Studies have suggested that treatment with antioxidants (such as vitamin A palmitate) may slow the disease from getting worse but they are debabtable.
Several clinical trials are in progress to investigate new treatments for retinitis pigmentosa. Microchip implants that go inside the retina are in the early stages of development for treating blindness associated with this condition.
I tried to look for the study but it seems it has not yet been published. I am a member of many journals and it is not there in them. It is not possible to get a hold of it, unless it is published. Thanks.
There is a big study going on concerning Retinitis Pigmentosa at United States, Kentucky. You can read about it by following this link http://clinicaltrials.gov/ct2/show/NCT00345917