Unraveling the ‘outdoor effect’ on nearsightedness

Unraveling the ‘outdoor effect’ on nearsightedness

Evidence indicates that time outside can act as a key biological trigger in diminished myopia rates, but how this "outdoor effect" becomes an ocular catalyst remains cloudy at best.

"Optometry needs to stay on top of this topic and be ready to offer options to their patients when they're proven effective."

That question is at the center of ongoing research from The Ohio State University (OSU) College of Optometry to identify the physiological responses activated by active time outdoors and how these factors can be adapted into a new approach toward nearsightedness.

Building off a previous study in 2007 that showed a correlation in greater outdoor time and reduced likelihood of nearsightedness among children, researchers are focusing attention on sunlight—both ultraviolet and visible light—for potential influences on the growing eye.

Given that Ultraviolet B (UVB) light stimulates production of vitamin D—a nutrient that is thought to support muscle tissue function around the lens of the eye—sunlight might help bolster tissue that maintains the proper eye shape. Some studies have shown myopic people have lower vitamin D levels, but it's not known if the nutrient exhibits a direct biological effect. The study seeks to define an accurate measurement of vitamin D to build toward defining its role.

Separately, researchers are also scrutinizing visible light for the way it reacts with cells to release dopamine, a neurotransmitter that could slow ocular growth. Researchers plan to measure dopamine release using a test that measures pupillary reaction to light and cellular response.

'Exciting time in refractive error'
Karla Zadnik, O.D., Ph.D., OSU College of Optometry dean and study collaborator alongside Donald Mutti, O.D., Ph.D., says the research is very much ongoing and will help set the stage for further large-scale study.

"There are decades of research in that first observation that we were fortunate enough to make [in the 2007 study]," Dr. Zadnik says. "It has led to more ongoing research both basic and patient-oriented than I could have predicted."

Based on the current research, should people make their kids stay outside all day? Of course not, Dr. Zadnik says, but "outdoor time isn't the worst thing in the world." It's still too early to make a clear determination about sunlight's role in myopia.

However, the research is drumming up quite a bit of interest, both from practitioners and patients. Just like the saying, 'everything old is new again,' Dr. Zadnik says myopia is a "hot topic again."

"Don't neglect going to some myopia lectures that tell you what's hot and new, because it's an exciting time in the study of refractive error, and it's causes and treatments," Dr. Zadnik says.

"You're seeing more and more patients asking, 'Is there anything that can be done for my child's nearsightedness?' Optometry needs to stay on top of this topic and be ready to offer options to their patients when they're proven effective."

December 9, 2014

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