Antidepressant medications, such as Prozac (fluoxetine, Eli Lilly), could be used to treat amblyopia, according to a study in the April 18 issue of Science. Researchers demonstrated that continuous administration of fluoxetine reinstates ocular dominance plasticity in adulthood and promotes the recovery of complete visual function in amblyopic adult animals.

In early childhood, neuronal connections are in a highly plastic state. During this specific time, the weaker eye of an amblyopic child may regain strength by patching the stronger eye. In adolescence, however, this critical period closes, and neuronal plasticity is greatly reduced.

Yet, according to the researchers, treatment with fluoxetine reopened the critical period of plasticity in the visual cortex of adult rats. In this experiment, the stronger eyes of amblyopic adult rats were patched and fluoxetine was administered until vision in the weaker eyes improved.

The researchers concluded that the restored plasticity induced by fluoxetine facilitated reorganization of neuronal connections in the cerebral cortex. This, in turn, allowed for strengthening of the weaker eye in the amblyopic adult rats.

However, fluoxetine only improved vision in the weaker eye if the dominant eye was patched. This finding indicates that auxiliary stimuli are still required to produce the desired visual outcome, the researchers said.

These findings may be quite significant, says Dominick Maino, O.D., M.Ed., professor at Illinois College of Optometry. To see positive results, the test subjects still required vision therapy; however, Prozac seemed to work as an effective primer for the therapy.

However, Dr. Maino expressed concern about the long-term side effects of Prozac. Continued use of Prozac has been associated with suicide, severe anxiety, glaucoma and visual field defects. So, if Prozac becomes a useful treatment for adult amblyopia in the future, we will have to be very cautious.

Maya Vetencourt JF, Sale A, Viegi A, et al. The antidepressant fluoxetine restores plasticity in the adult visual cortex. Science 2008 Apr 18;320(5874):385-8.

Vol. No: 145:05Issue: 5/15/2008