Light to restore sight

The brain after birth demonstrates remarkable plasticity—what we sense in those early months helps to fine-tune and optimize our neural circuitry. Unfortunately, these circuits become less malleable as we mature, making it difficult to recover from brain diseases or the adverse effects of early experiences as an adult.

MIT Picower Professor of Neuroscience Mark Bear has dedicated his career to finding ways to restore this youthful plasticity in cases of brain-based visual disorders. Early deprivation of vision in one eye modifies the brain’s visual cortex in a way that causes a condition called deprivation amblyopia, a severe impairment of binocular vision. This condition is permanent if not corrected within the first few months of life.

Bear’s studies with adult mice show that the brain can regain its plasticity after vision deprivation, however, in a finding that “seems so outlandish that it can hardly be true,” he says. Brief doses of flickering light, delivered at the specific frequency of 40 Hz to adult mice, sends the neural circuitry in their visual cortex back into a juvenile, plastic state that allows them to recover from long-term deprivation amblyopia.

With this remarkable success in mice, the time is right to test this noninvasive and safe treatment in people, says Bear. He is collaborating with MIT’s Ed Boyden, Y. Eva Tan Professor in Neurotechnology at the McGovern Institute and HHMI, to develop a headset that allows people to watch engaging video as they receive full-field light stimulation. Bear is collaborating with Chief of Ophthalmology David Hunter, Professor of Ophthalmology Eric Gaier and Instructor of Ophthalmology Ana Costa at Boston’s Children’s Hospital on a small clinical trial of the headset in 20 people.

Facing funding headwinds

The clinical trial offers an exciting opportunity to learn more about exactly how the flickering light treatment affects the visual cortex to restore its plasticity. Previous research by Bear and his colleagues offers clues to what some of the changes might be, but he is also looking forward to examining changes in gene expression in the cortex after light exposure. Traditional funding from places such as the National Institutes of Health “might be possible for this work, but the findings are so novel that we will face strong headwinds, explains Bear. “Indeed, our initial attempts at even an ‘exploratory’ grant have failed. Bose funding gives us the runway we need.”

Flickers of hope

This research directly addresses an unmet medical need for treatment of amblyopia, which affects about 3% of all adults older than age 20. But Bear also believes it could have an enormous impact on our understanding and treatment of all brain-based visual disorders including cerebral visual impairment, the leading cause of blindness in children.

The clinical trial is an exciting way to move the science forward, says Bear: “We basic scientists occupy a different universe than clinicians and jumping from an animal model—in our case, a mouse—to a human is challenging, time consuming, and expensive. However, we now have an unexpected opportunity to bridge this divide at a low cost using a noninvasive procedure validated in mouse experiments.”