The retina is a lining of tissue located at the back of the eye that is sensitive to light.
A light-sensitive tissue located on the inner surface of the eye, the retina is crucial for sharp central vision. Various disorders – some degenerative – can affect the retinas. In cases where visual acuity has been severely impaired and no other therapeutic intervention is available, a retinal transplant may be attempted in an effort to improve vision.
A number of diseases can cause damage to the retina, including macular degeneration.
To achieve visual perception, images seen through the lens of the eyes are focused on the retinas, which then convert them into electrical impulses and transmit them to the brain via the optic nerve. Healthy retinal tissue is typically red due to the abundance of blood vessels that supply it with nutrients. An ophthalmologist can easily examine the retina during a routine eye exam. Changes in the color of retinal tissue can be indicative of disease. A number of diseases can damage the retina, including retinitis pigmentosa and macular degeneration.
Changes in the color of retinal tissue can be indicative of disease.
Retinal tissue transplantation is an experimental procedure, used only when all other treatment options have been exhausted and in cases where there is extensive tissue damage and complete loss of vision. There are two types of transplant options, whole retinal and stem cell transplants. Stem cell transplants have not been successful, as the cells do not appear to differentiate into retinal cells, a process necessary for visual improvement. Clinical trials involving transplantation of a small piece of all retinal tissue have proven to be moderately successful, with a large percentage of patients experiencing some degree of improvement in visual acuity. It is thought that the transplanted cells could eventually replace the patient’s damaged cells.
Smoking increases the risk of macular degeneration, which causes scarring of the retina.
There are several concerns regarding retinal transplants, as the tissue used in clinical trials often comes from aborted fetuses. Approval to replicate the technique on a larger scale, using fetal tissue, could pose an ethical issue. Medical studies indicate that transplanted retinas can release growth factors into the recipient’s eyes and this can help their own retinal cells to recover from damage. Therefore, it is unclear whether whole retinal tissue transplants are necessary for visual improvement. Improvements in visual acuity are typically reversed one to two years after retinal transplantation, although in isolated cases they have lasted up to six years after treatment.
Retinal transplants are experimental procedures and improvements usually only last one to two years.
No immunosuppressive drugs appear to be necessary after a retinal transplant and, according to medical studies, there have been no cases of transplanted tissue rejection. The procedure is experimental. More research is needed to determine the safest retinal transplant method that offers the best sustainable improvement in visual acuity.