Lazy Eye: Going Dark to Restore Vision


VOICEOVER: Lazy eye, a type of amblyopia,
is a condition in which the brain and the eyes are not stimulated equally, causing the
brain to favor one eye over the other. ELIZABETH QUINLAN: the brain basically learns to ignore
the signal from the weak eye. And so the individual becomes monocularly
blind. Amblyopia is very easy to reverse in children,
but almost impossible to reverse in adults because adult brains lose the plasticity to
allow it to reverse. VO: If patients are young, this condition
can be treated by patching the strong eye, forcing the brain to readjust the input from
the weak eye. But as the patients age, it becomes increasingly
more difficult to fix. Though there still may be a solution: Total
darkness. QUINLAN: We teamed up with a great group from
SUNY Optometry that’s led by Ben Backus, currently running an NIH-sponsored clinical trial to
ask if visual deprivation can enhance plasticity in the visual cortex of adults, and if we
can use that plasticity to re-teach amblyopic humans how to see. VO: But before this idea could be applied
to human subjects, it had to first be tested on rodents in a lab setting. QUINLAN: We reduced visual experience by putting
our test subjects, in this case rodents, in the dark. By reducing visual input by placing the subjects
in the dark, we were able to get the visual parts of their brain to re-express plasticity
like a juvenile. VO: After the success of these laboratory
experiments, it was clear that humans were the next step. QUINLAN: Adult amblyopes that have been told
that they’re too old to have their amblyopia reversed are being placed in the dark for
10 days, and we’re testing the idea that that visual deprivation is going to enhance plasticity
enough that we can reteach the weak eye how to see. This is a really exciting example of translational
work, taking results from a basic science lab like mine, and translating that to clinical
practice and clinical trials. VO: Subjects in the experiment lived in a
completely blacked out residence for 10 days. QUINLAN: We’ve tested this in several human subjects, some amblyopic human subjects and
some non-amblyopic human subjects, and they tolerate being in the dark very well. They learn how to navigate based on touch
and also based on sound. It’s a very structured time in the dark. We have exercise time, they have books on
tape. VO: Instead of being bored or claustrophobic,
the test subjects found the experience to be calming and stimulating. Some even experienced vivid hallucinations
in the absence of visual input. QUINLAN: Every person who’s been in the dark
so far has said it was an enjoyable experience, and they came out of the dark more relaxed
than when they went in the dark. VO: For more than a decade, Quinlan’s lab
has worked on treatments for amblyopia using rodents. Quinlan is hopeful that the promising results
in mice and rats might one day translate to success in human subjects. When it comes to rodents… QUINLAN: Visual deprivation rejuvenated the
brain. Importantly, this plasticity that we could
re-engage with visual deprivation, was sufficient to allow us to teach the amblyopic subjects
how to see.

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