The Clinical Importance of Retinal Transplantation
Retinal transplantation research targets macular degeneration (AMD) and retinitis pigmentosa (RP). Other diseases that might be helped are Stargardt’s disease, familiar drusen, rod cone dystrophy and dystrophy of retinal pigment epithelium after neovascular membrane removal. The causes for these diseases are largely unknown, and there is currently no treatment available that can reverse the degenerative processes. However, there is hope for patients that still have the inner part of retina functional, which many affected patients still have, with its retinal ganglion cells that communicate with the brain.
The Food and Drug Administration (FDA) that supervises clinical trials approved in 1999 to use this procedure to show the safety in very blind human patients (IND # BB-IND8354). A Phase I clinical study was published 2002 and showed that the surgery was feasible and the instruments functioned fine and it was safe to use for the patients. Then FDA allowed the surgery on blind people with better vision. A Phase II study was published 2008 that showed that incurable diseases such as macular degeneration (AMD) and retinitis pigmentosa (RP) not only could be halted but also be improved. The best patient with RP improved from 20/800 to 20/200 after one year and remained so for six years.
As can be seen in the publication list, there has been a string of encouraging research results that has led to the present stage. The most encouraging is that it is very likely to obtain improved results in the next series of patients. We have several improvements handy. We have e.g. basic research results in animals that show that we can improve the function of the transplant more than 20% by introducing a certain growth (trophic) factor. We have also visual stimulation therapy to introduce for the patient to stimulate the function of the transplant.
The prospects look very good that retinal transplantation can be a beneficial therapy for retinal diseases. However, the restricted availability of the immature donor tissue can never meet the demand. Still thousands of patients could be helped by this procedure. With our successful results from freshly harvested tissue as a template, Dr. Magdalene J. Seiler (UC Irvine) is also working with to make layered sheets of retina from stem cells to create an unlimited source of donor tissue, but any clinical application is unfortunately undetermined in the future. However, the method with the most potential immature cells is available now.