Italian researchers may have found a drug to treat amblyopia, or lazy eye. A study published in April in Science has demonstrated that Prozac, or fluoxetine, has one clear beneficial effect on the disorder, at least in rats: It can promote plasticity in the vision-processing part of the brain, a phenomenon formerly observed only in early development.
In children with amblyopia, one eye does not receive enough visual input, which causes the other eye to take over most of the visual processing in the brain. If the input problem is not corrected early in childhood, when the brain is still malleable, it can lead to permanently defective vision or blindness in one eye.
In a two-part study of adult rats treated with fluoxetine at levels comparable to those of people treated for depression, the scientists both induced amblyopia and cured it. First they sealed one eye, essentially instigating a case of untreatable lazy eye in an adult animal. In a second stage, they sealed the good eye of adult rats that had amblyopia. Over the four-week period of treatment with fluoxetine, the rats recovered full vision and behaved as normally sighted animals do.
The mechanism of the rats’ recovery from amblyopia is uncertain, but the researchers believe that fluoxetine opens pathways to genes that regulate plasticity, allowing modification of neuronal circuitry in the adult animal’s brain. Changing the brain circuitry improves or restores vision.
Whether the same effect could be attained in the much more complex nervous systems of adult humans is unknown, says José Fernando Maya Vetencourt, the lead author of the study and a researcher in neurobiology at the Scuola Normale Superiore in Pisa, Italy. “We’re working with adult amblyopic patients to evaluate the possibility,” he says, “but it will take us a few years before we can draw any conclusion.” Maya Vetencourt adds that the findings may also shed light on the treatment effects of antidepressants and on the pathophysiology of mood disorders.