March 5, 2009

Shedding Light on a Blinding Condition

Researchers are working to shed new light on the most common form of blindness among adults, and their findings are suggesting an innovative way forward for treatment.

Macular degeneration develops when the central part of the retina loses light-sensitive cells. The neurons responsible for relaying visual messages to the brain remain intact, but without the cells, people lose the sharp central vision needed for everyday tasks like reading or driving.

Previous research found these neurons begin responding to stimuli in another area called the preferred retinal locus, or PRL, when the central section is no longer available. That's why people with macular degeneration often roll their eyes upward in order to see something they would normally see straight on.

In this study, MIT investigators wanted to see if this chronic use of the PRL causes permanent changes in the visual cortex or whether the neurons would respond to stimulation at any peripheral location on the retina.

In a study involving two patients, they found the latter was the case. Functional magnetic resonance imaging revealed the deprived neurons responded equally to both the preferred PRL and the nonpreferred other peripheral area.

This, they conclude, shows the adult brain is fairly "plastic" "“ meaning if scientists could find a way to replace the light sensitive cells lost to macular degeneration, people may be able to recover their clear central vision.

SOURCE: Journal of Neuroscience, published online March 3, 2009


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