Dark Therapy Found Promising for Lazy Eye Treatment

Researchers from Carnegie Mellon University are examining the mechanics that underlie a treatment for people with amblyopia, also known as "lazy eye," in a new pilot study.

Amblyopia is a vision development disorder that occurs in childhood. It is caused by the brain and the eye not working together properly, resulting in reduced vision in one or both eyes. Transient dark exposure, in which a patient gets an occlusion that caused their amblyopia removed and lives in darkness for a few days, is one therapy that shows promise for treating the problem in adult patients.

The Mellon College of Science and the College of Engineering at Carnegie Mellon University conducted a study that showed evidence that, a week after temporary dark exposure, the brain's neural networks adjust how they process visual information, enhancing vision. The findings were published in eLife.

"One of the big things in neuroscience is to try to understand how we have stable perception," said Sandra Kuhlman, assistant professor of biological sciences at Carnegie Mellon and the head of the Kuhlman Lab. "The field is now able to identify adaptive properties of neural circuits on long time scales. That's really important to understand how neural function underlies basic sensory processes."

The study was developed by Brian Jeon, a postdoctoral scholar and graduate of the Department of Biological Sciences at Carnegie Mellon, while he was a Ph.D. candidate working in Kuhlman's group.

"Transient dark exposure is a treatment that people are exploring in humans," Jeon said. "We said, 'hey, maybe this has to do with how the brain encodes information, and maybe that gets disrupted when you remove inputs for an extended period of time." We found there is some room for change, but actually, the system is very resilient."

The Study

In the study, adult mice's brain activity is monitored using two-photon calcium imaging both before and after a brief period of darkness exposure. With the help of this method, researchers can measure complete networks of neurons in living models.

The study started with mice being exposed to visual stimuli, and the brain reactions were recorded. The same stimuli were again shown to the mice after they had been in the dark for eight days, and their visual reactions were likewise recorded.

"Brian's data helps shed light on the various, complex factors that drive plasticity in the visual cortex, and bring us one step closer to understanding how eye injury and disease might affect visual perception," said Steven Chase, professor of biomedical engineering and a co-author on the paper.

Within a few days of exposure, the mice showed some difficulties with visual processing, but they were back to normal within a week.

The methods developed for this study are intended to be used to longer-term studies or studies with younger mice. They also intend to simulate and research additional neurological and psychiatric diseases using the two-photon calcium imaging method.

"There's so many things we don't understand at a cell type specific level in neural circuits," Kuhlman said. "We hope that the analytical approach will be useful for other researchers."