When it is not present RP is definite. There are over 120 million light receptors in the retina. The ABCR gene is in the cones, not in the rods. There is a theoretical possibility that some unaffected genes might be injected into the bone marrow hopefully to regenerate unaffected genes that would find its way to the retina. Laser treatment- for Drusen causes it to shrink somewhat.
Tumors have a way of tricking cells into making blood vessels grow to nourish it.
By developing inhibitor cells it shrinks the tumor. This theory is being applied to the Drusen somewhat successfully. Like new recruits into the service they have not been trained. Therefore in implanting them under the retina which does not reject these cells for some reason does reproduce new retinal cells. This holds a lot of promise for future surgeries.