In the study, researchers performed the experimental transplant procedure in ten patients with vision loss resulting from retinal degeneration: six patients with RP and four with the "dry" form of AMD. Although they have different causes, both RP and AMD lead to destruction of the light-receiving (photoreceptor) cells of the retina.
All patients underwent transplantation of fetal retinal cells. The cells were implanted along with their attached retinal pigment epithelium, which plays a key role in nourishing the photoreceptor cells. The concept behind the procedure was that the new cells would grow to replace the damaged photoreceptor cells, connecting to the patient's remaining retina.
Follow-up testing showed visual improvements in seven of the ten patients: three of the patients with RP and all four patients with AMD. Although vision remained in the "legally blind" range for all patients, the gains in vision were significant and measurable.
In one patient with RP, the visual improvement was still present up to six years after surgery, while vision in the opposite (untreated) eye continued to deteriorate. In the same patient, specialised tests showed a 27 percent increase in light sensitivity in the treated eye.
There were no problems with rejection of the transplants by the patients' immune systems, despite the lack of a perfect immunological match between the transplant donors and recipients. This likely reflected the special "immunologic protection" of tissues within the eye.
The experimental transplant procedure was designed on the basis of animal studies. Previous "phase I" studies established the safety of the procedure. The new "phase II" trial provides the first evidence of improved vision. Much further research will be needed to determine the potential for retinal transplantation to improve vision in patients with these diseases.
MEDICA.de; Source: Elsevier