There's good news on the research front for those with severe damage to the surface of the eye, for whom corneal transplants have not been an option. A recently published article in the New England Journal of Medicine describes a successful approach that is being used to restore vision to numerous patients with limbal stem-cell deficiency. The cornea is the transparent structure of the eye, through which light from images pass into the deeper structure until they reach the retina and are processed by the brain. It is critical that the cornea remains clear, because any scarring or opacification will block light from getting into the eye. If a person has a vision-threatening injury to the cornea, it can usually be treated by removing the damaged tissue and replacing it with a new cornea (corneal transplant). However, this procedure has not been successful in patients who have significant damage to the outermost surface cells called the epithelial cells. Normally these epithelial cells can regenerate if they are injured, but there are certain diseases or injuries (such as chemical burns) that kill the pre-cursor stem cells for the epithelium. These stem cells are normally found in the limbus, which is the region where the cornea (the clear, anterior part of the eye) meets the sclera (the white part of the eye). If a person has limbal stem-cell deficiency, most treatments are unsuccessful, and vision will not be restored. Numerous researchers and eye doctors have been working on methods to replace damaged epithelial cells for these patients. During the past 10 years, researchers at the University of Modena's Center for Regenerative Medicine in Italy have treated more than 200 patients who have lost their vision due to chemical burns with techniques to replace damaged limbal stem cells. They collect limbal stem cells from the "good" eye that has not been damaged and grow the cells, which can give rise to normal corneal epithelial cells, which are then placed onto the damaged eye. The transplanted stem cells begin to repopulate the limbus of the damaged eye and produce normal epithelial cells that grow and cover the damaged cornea. The new, healthy epithelium that grows back provides the protection and nutrition required by the underlying cornea. The patient then can have a corneal transplant or laser procedure to remove and replace the deeper, damaged, scarred corneal tissue. The Discovery Eye Foundation supports ongoing research at the University of California, Irvine's Gavin Herbert Eye Institute to develop new methods to restore vision using stem cells for the cornea and retina – part of a novel, exciting field of regenerative medicine that will change the future of medical treatment. Using a similar approach to the University of Modena, the UCI cornea specialists are able to treat these conditions by performing limbal stem cell transplants to repopulate the damaged corneal epithelial cells. This exciting approach has improved the vision of patients with severely damaged corneas due to limbal cell deficiency. Dr. Henry Klassen and his team are investigating the potential of human retinal progenitor cells to prevent or restore vision loss for people with retinal dystrophies or macular degeneration. His ongoing work has been successful and we are hopeful human trials will begin in the not-that-distant future. –M. Cristina Kenney, MD, PhD.
Posted September 2010