Myopia cell discovery

Myopia cell discovered in retina: Dysfunction of cell may be linked to amount of time a child spends indoors

Date:
February 6, 2017
Source:
Northwestern University
Summary:
Scientists have discovered a cell in the retina that may cause myopia when it dysfunctions. The dysfunction may be linked to the amount of time a child spends indoors and away from natural light. This discovery could lead to a new therapeutic target to control myopia. More than a billion people in the world have myopia, whose incidence is rising and is linked to how much time people spend indoors as children.
FULL STORY

 Cells in the eye could be over stimulated by indoor light spectrum, causing damage, say researchers.
 
                                                             
             The light rays are not focused on the retina in a myopic eye. The focal point falls in front of the
              retina.
 

Northwestern Medicine scientists have discovered a cell in the retina that may cause myopia when it dysfunctions. The dysfunction may be linked to the amount of time a child spends indoors and away from natural light.

“This discovery could lead to a new therapeutic target to control myopia,” said Greg Schwartz, lead investigator and assistant professor of ophthalmology at Northwestern University Feinberg School of Medicine.

More than a billion people in the world have myopia, whose incidence is rising and is linked to how much time people spend indoors as children.

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,” Schwartz said.

It has long been long known the retina contains a signal to focus the image in the eye, and this signal is important for properly regulating eye growth during childhood.

“But for years no one knew what cell carried the signal,” Schwartz 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.”

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.

How too much time indoors may trigger myopia

The indoor light spectrum has high red/green contrast, which activates these clusters of photoreceptors in the human eye, creating the equivalent of an artificial contrast image on the retina. It’s 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, Schwartz said.

 

To conduct the study, Schwartz and co-author Adam Mani, a postdoctoral fellow in ophthalmology at Feinberg, used microscopic glass electrodes to record electrical signals from cells in a mouse retina while presenting patterns of light on a digital projector.

The next goal is to find a gene specific to this cell. Then scientists can turn its activity up or down in a genetic mouse model to try to induce or cure myopia.

The study is part of Schwartz’s larger body of research to reverse engineer the retina by identifying new retinal cell types in mice. The retina has about 50 types of retinal ganglion cells, which together convey all the information we use to perceive the visual world. Each of these cells provides different visual information — such as colour or motion — about any point in space.

Schwartz, who is funded by the National Institutes of Health (NIH), wants to identify the new cells by their specific function, analyze their genetic signatures and understand how the cells are interconnected within the retina and to their targets in the brain. His research could lead to gene therapy to treat blindness and to improve the function of artificial retinal prosthetics.

 


Story Source:

Materials provided by Northwestern University. Original written by Marla Paul. Note: Content may be edited for style and length.


Journal Reference:

  1. Adam Mani, Gregory W. Schwartz. Circuit Mechanisms of a Retinal Ganglion Cell with Stimulus-Dependent Response Latency and Activation Beyond Its Dendrites. Current Biology, 2017; DOI: 10.1016/j.cub.2016.12.033

 


Level of education is more decisive than intelligence for the development of short-sightedness

Environmental factors such as education and leisure activities have a greater influence on the development of short-sightedness or myopia than the ability to think logically and solve problems. Myopia and the so-called “fluid intelligence” of a person are certainly related, but only indirectly through the duration of education. This is the conclusion of researchers at the Mainz University Medical Center involved in the study “Myopia and Cognitive Performance: Results from the Gutenberg Health Study.” The results of the study appeared in the October issue of the specialist journal Investigative Ophthalmology & Visual Science.

Myopia, also known as short-sightedness or near-sightedness, is the most common disorder affecting the eyesight and the condition is on the increase. Severe short-sightedness is one of the main causes of impaired vision. In addition, it is closely associated with an increased risk of secondary complications such as retinal detachmentmacular degeneration, premature cataracts, and glaucoma. Because myopia can be easily treated in the early stages, although it cannot be fully cured, insight into the causes of the disease is of central importance.

“We know from earlier studies that a higher level of education frequently goes hand-in-hand with the development of short-sightedness,” said Professor Norbert Pfeiffer, Director of the Department of Ophthalmology at the University Medical Center of Johannes Gutenberg University Mainz (JGU). Together with Professor Alireza Mirshahi, Director of the Bonn Dardenne Eye Clinic, and Professor Josef Unterrainer, who heads the Department of Medical Psychology and Medical Sociology at the University of Freiburg, Pfeiffer was in charge of the study “Myopia and Cognitive Performance: Results From the Gutenberg Health Study,” which was the subject of the recent publication. The core question being considered is whether short-sighted people are not only better educated but also more intelligent.

Based on their findings, the research team lead by Pfeiffer, Mirshahi, and Unterrainer have come to the following conclusions: Considered in isolation, cognitive ability and, thus, intelligence apparently plays a significant role in the development of short-sightedness. But when the researchers took into account already identified potential influencing factors, they discovered that the number of years over which an individual received education exhibited a more direct and closer relationship with short-sightedness than cognitive ability. This means that it is only through educational attainments that cognitive ability is linked to myopia. In other words, the level of education rather than intelligence is more decisive for development of short-sightedness. In the case of two equally intelligent people, it is thus most probably the one who attended school for longer and has the better educational qualifications who will become myopic and experience more defective vision.

For their study, the research team analyzed data collected within the framework of the Gutenberg Health Study conducted by the Mainz University Medical Center. This is one of the largest population-based research studies in the world. The sub-cohort consisted of some 4,000 subjects aged 40 to 79 years. The researchers used the Tower of London (TOL) test to measure cognitive functioning. The 20-minute test assesses cognitive ability by mentally planning ahead and problem solving. In order to diagnose myopia, the researchers examined the refractive power of the eyes of subjects, thus determining how much their eyes had to adjust to produce a sharp image. Short-sightedness is characterized by negative diopter values. In the study, myopia was diagnosed when the identified diopter value was less than or equal to 0.5.