(February 8, 2012 - Insidermedicine)

Early research with gene therapy is bringing vision back to patients suffering from Leber congenital amaurosis (LCA). The latest study, in which patients were successfully treated for the second time, is published in the February 8 issue of Science Translational Medicine.

Here are some recommendations for conducting pediatric eye examinations, from the American Optometric Association:

•    Children aged from birth to 2 years, 11 months of age generally perform best if the examination takes place when they are alert. Examination early in the morning or after an infant's nap is usually most effective.

•    Because infants tend to be more cooperative and alert when feeding, it is also helpful to suggest that the parent bring a bottle for the child.

•    Age-appropriate examination and management strategies should be used. Major modifications include relying more on objective examination procedures and performing tests considerably more rapidly than with older children.

Researchers out of The Children's Hospital of Philadelphia and the University of Pennsylvania injected a vector containing a normal RPE65 gene into the eyes of three adults with LCA. It is a mutation of just this gene is the cause of the patients’ blindness. All three of these patients had received this same treatment in one eye in 2009 with good results. This second trial involved treatment of the previously untreated eye.

The investigators were concerned that a second treatment could trigger a vaccine-like immune response that might not only prevent the second treatment from working but also reduce the benefits that patients’ obtained with the first treatment. Fortunately, no such immune response was observed in any of the three patients. During a six month follow-up period, patients experienced the most significant improvements in light sensitivity, including improved pupillary response to changes in light intensity. Two out of the three patients were able to navigate an obstacle course in dim light, and functional magnetic resonance imaging (fMRI) revealed increased activity in the area of the brain responsible for vision in both eyes in response to visual stimuli.

Today’s research offers proof of principle that gene therapy is both an effective treatment for LCA, and possibly other retinal diseases, and is safe even with repeated treatments.