The discovery of a specific retinal cell could lead to a new therapeutic target to control myopia, a refractive error that affects more than a billion people in the world. Scientists at Northwestern University, Feinberg School of Medicine in Chicago believe the retinal cell may cause myopia when it dysfunctions and that the dysfunction may be linked to the amount of time a child spends outdoors and away from natural light.
This new development complements other research supporting the benefit of outdoor activity and bright light exposure in the rush to reduce myopia progression. The newly discovered retinal cell – which is highly sensitive to light – controls how the eye grows and develops. If the cell instructs the eye to grow too long, images fail to be focused on the retina, causing nearsighted vision and a lifetime of corrective glasses or contact lenses.
“The eye needs to stop growing at precisely the right time during childhood,” said A/Prof. Schwartz.
It has long been known that the retina contains a signal to focus the image in the eye, and this signal is important for properly regulating eye growth during childhood.
It has long been known that the retina contains a signal to focus the image in the eye
“But for years no one knew what cell carried the signal,” he said. “We potentially found the key missing link, which is the cell that actually does that task and the neural circuit that enables this important visual function.”
A/Prof. Schwartz named the cell, “ON Delayed,” in reference to its slow responses to lights becoming brighter. The cell was unique among many other cell types tested in its exquisite sensitivity to whether an image was in focus.
He described the neural circuit as the diagram that reveals how this cell is wired to other cells in the retina to acquire this unique sensitivity.
Too Much Time Indoors May Trigger Myopia
A/Prof. Schwartz said the indoor light spectrum has high red/green contrast. This activates the clusters of photoreceptors in the human eye, creating the equivalent of an artificial contrast image on the retina. It is likely the human version of the ‘ON Delayed’ retinal ganglion cell would be overstimulated by such patterns, causing aberrant over-growth of the eye, leading to myopia.
He and co-author Dr. Adam Mani, a postdoctoral fellow in ophthalmology, used microscopic glass electrodes to record electrical signals from cells in a mouse retina, while presenting patterns of light on a digital projector.
Their next goal is to find a gene specific to this cell. Once found, they believe they could turn the gene’s activity up or down – in a genetic mouse model – to try to induce or cure myopia.
The retina contains about 50 different types of retinal ganglion cells. These collectively convey the information we use for vision. Each cell type conveys different visual information, like colour and motion, relating to any point in the visual field.
