Unique retinal cell dysfunction triggers myopia?

The interplay between indoor lighting and a newly identified retinal ganglion cell might signal the wrong message, triggering myopia-inducing eye growth at a crucial time in children's development.

Published online in the journal Current Biology, a Northwestern University study claims to shed light on a cellular catalyst—long described but never identified—that activates eye elongation and eventual myopia in the absence of natural lighting. It's a claim that could help in understanding an observed "outdoor effect" related to myopia development.  

This newly discovered "ON Delayed" (OND) retinal ganglion cell controls how the eye grows and develops. So named for its unusually long latency to light stimulation, OND RGCs are unique among other cells with an "exquisite sensitivity to whether an image was in focus," according to a Northwestern news release. OND RGC dysfunction could cause the eye to overgrow, resulting in myopia.  

Using a mouse proxy, researchers recorded electrical signals from retinal cells while presenting patterns of light on a digital projector. Indoor light, which contains a high red/green contrast, would activate clusters of photoreceptors and create an artificial contrast image. Therefore, researchers surmised that such light would overstimulate human OND RGCs, sending a growth signal.  

As study lead investigator Greg Schwartz, Ph.D., notes, this signal—important for properly regulating children's eye growth—was long-known to originate in the retina, but researchers were unable to identify which particular cell carried the signal.  

"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," Dr. Schwartz notes.  

By 2050, half of the global population will be myopic with one-fifth of those at significantly increased risk of blindness, according to a 2016 World Health Organization report. In the U.S., myopia affects nearly 33% of the population, but in some east Asian countries, the toll is much higher. South Korea, for instance, noted myopia rates in 19-year-olds jumped from 18 to 96% in the past 50 years.  

Andrew Morgenstern, O.D., AOA consultant, says such research provides a better understanding of the myopic picture.  

"If we can identify a cell in the retina that's directly linked to myopia development, then that allows us as doctors of optometry not only a potential pathway for preventive treatment options, but also an opportunity to educate the parents of our youngest patients about myopia-related ocular disease, management of environmental causes, and of course, myopia control."  

International symposium examines myopia control  

Optometry's expertise and depth of knowledge uniquely positions the profession on the forefront of myopia. That's why at the 2017 Optometry's Meeting ^®, June 21-25, in Washington, D.C., leading international experts in myopia will join together to discuss this growing epidemic and methods for controlling its development.  

The "Chinese and U.S. Myopia Control Symposium," Thursday, June 22, features speakers from both countries in a three-hour continuing education (CE) program that will demonstrate myopia management methods utilizing contact lenses. This workshop will allow participants greater comfort and understanding of various contact lens methods, patient selection, topographical assessment, instrumentation and identification of problems.  

"This one-of-a-kind, innovative symposium brings together both U.S. and Chinese experts, presenting their innovative work sessions, data, methods and research to educate doctors of optometry and paraoptometrics on this rapidly advancing, global health concern," Dr. Morgenstern, symposium moderator, says.

"The alarming prevalence of myopia worldwide hasn't reached the public's radar quite like we would hope, but nonetheless it must be addressed. Optometry can finally do something to help control this near-epidemic-level eye and vision condition."