Research by Linda McLoon, Ph.D., has shown that retinal ganglion cells previously thought to be beyond rescue might be repairable.
Many types of eye injuries can cause irreversible damage and vision loss. For example, when the eye’s retina and optic nerve are deprived of oxygen, the consensus among clinicians is that nothing can be done to restore the patient’s vision if lost.
Exciting new research in the University of Minnesota Medical School gives hope to those who might have this type of “stroke” of the optic nerve in the future.
After eye injury, whether from trauma, stroke, or blood clot, retinal ganglion cells—which collectively transmit information from the retina to the brain—appear to die quickly.
But some of those cells are simply damaged, not dead, according to Linda McLoon, Ph.D., professor of ophthalmology and neuroscience at the University. “We have found that there is a window of time in which to administer protective molecules that should be able to rescue those damaged cells,” she explains.
The next challenge? Delivering these protective molecules, also called neurotrophic agents, across the blood-brain barrier. (The retina and optic nerve are extensions of the brain.) McLoon’s lab has found that intranasal drops administered in animal subjects can reach the retinal ganglion cells.
“What we have found is exciting, but of course we have much more to learn before this can be applied to humans,” says McLoon. “How soon would these drops need to be administered, and how often? Is one dose enough?”
A 1999 multicenter study found that neither surgery nor corticosteroids restored vision for patients who had suffered compressive or ischemic optic nerve injury. McLoon’s research points in a more promising direction.
“Intranasal delivery is appealing because it is easy for patients,” McLoon says. “I could imagine having intranasal drops available in every emergency room or trauma center and then sending drops home with the patient. Even if a patient had to administer them once a day, who wouldn’t willingly do that in order to save their eyesight?”
The research is still in its early stages, however. Once the first set of experiments is completed, the model needs to be replicated in primates. Then comes a phase 1 clinical trial for qualified patients, to be run by neuro-ophthalmologist Michael Lee, M.D.
“Whenever I undertake a study, I ask myself if I would want my mother to undergo the treatment, or whether I would undergo it myself,” McLoon says. “And if the answer is yes, as it is in this case, then I know we’re using an approach that is reasonable from a clinical point of view.
“These drops we’re using are molecules our bodies already produce, so the study doesn’t bring with it the potential risks associated with some types of drug treatments,” she says.
To learn more about McLoon’s research, visit www.lkmcloon.umn.edu.