Northwestern scientists have discovered a new cell in the retina which may cause nearsightedness, or myopia, when disrupted.
People with myopia can see close objects clearly, but objects further away appear blurry, according to the American Optometric Association. The condition affects nearly 30 percent of the U.S. population and typically first occurs in children, according to the AOA.
As children grow so do their eyes and that process is “regulated very carefully inside the eye,” said Greg Schwartz, assistant professor of ophthalmology at Northwestern University Feinberg School of Medicine.
The retina contains a signal that controls how focused an image is and that signal plays an integral role in properly regulating how the eye grows, Schwartz said. “The eye has to be the right size to focus correctly on the retina.”
In the course of studying the eye, researchers discovered a new type of cell that had an “unusual response” to light. “Its response was half a second after the light came on. That doesn’t seem useful for normal vision,” Schwartz said, because most cells in the eye are usually much faster when responding to light.
To learn more about the cell, Schwartz and Adam Mani, a postdoctoral fellow in ophthalmology at Feinberg, studied this cell’s response to different patterns of light and images.
Researchers found the cell was slower to respond to light than any other cell and had an “enormous receptive field,” meaning it reported global light rather than light intensity in a defined space.
“Why would we want that? Most cells in the retina report what an image looks like in a small location. That’s how you can read a small letter on a screen,” Schwartz said. “But this [cell] reports a more global property of how in focus an image is. It makes sense for something that controls eye growth – either the whole image is in focus or it’s not.”
The newly discovered cell—named “ON delayed” in reference to its latent response to light—was also “exquisitely sensitive” to how in focus an image was. “We took images and blurred them at various degrees, and this cell could tell the fine gradations in blur better than any other cell could,” Schwartz said.
In addition to learning more about myopia, Northwestern’s discovery could also shed light on the correlation between the increased incidence of myopia in children and the time they spend indoors.
Fluorescent lighting has high amounts of red-green contrast which causes the eye to think an image is sharper than it really is, Schwartz said. The overstimulation of the eye could cause over-growth of the eye and lead to myopia.
“This cell, perhaps, brings all pieces of evidence together,” he said.
Current treatment options for myopia include eyeglasses, contact lenses or various surgical procedures.
This new finding could mean new therapeutic options for myopia, including pharmacological and genetic interventions.
In the process of studying the ON delayed cell, researchers found a drug that’s “likely to be fairly specific to this cell,” Schwartz said. “And if it is, it could be used for clinical therapy.”
But more research is needed first. Researchers are also actively searching for a gene that’s specific to the ON delayed cell. Once researchers discover that particular gene, they intend to manipulate it to see how it affects the eye, Schwartz said.
“Knowing the genetics of this cell, we would be able to detect a genetic predisposition for childhood myopia,” he added.
Schwartz and his fellow researchers are studying the mouse retina as a model in order to understand how all of the different cells function, “so one day we can really build an artificial retina for blind people,” Schwartz said.
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