The Myopia Pandemic

Aug. 28, 2015

By Medical Discovery News

The Myopia Pandemic

You’ve probably heard of pandemics – the plague, influenza, HIV – but you might not have seen coverage of the growing myopia pandemic. Before you consider bathing in sanitizer, you should know that myopia isn’t contagious. Another word for it is nearsightedness.

Myopia is a condition in which close objects are seen clearly but distant objects are blurred due to the elongation of the eye or too much curvature of the cornea. This causes light entering the eye focusing in front of the retina rather than on it. Myopia is different than hyperopia, which is the kind of nearsightedness that comes from growing older. In fact, the myopia pandemic is primarily affecting young people.

It currently affects 90 percent of the young adults in China, although 60 years ago it was 10-20 percent. In the United States and Europe it affects about half of all young adults, double what it was 50 years ago. Seoul has the highest incidence: 96.5 percent of young people in South Korea’s capital have myopia. An estimated 2.5 billion people will experience myopia by 2020.

Vision issues can be corrected with glasses, contact lenses, or surgery, but none of those fix the underlying defect. Eye elongation can stretch and thin parts of the inner eye, which can increase the risk of retinal detachment, glaucoma, cataracts, and even blindness.

Genetic causes have been discounted, so this rapid change has to come from something in the environment. More than 400 years ago, Johannes Kepler, an astronomer and expert in optics, wrote that his intense studying led to nearsightedness. Today, students are not only studying a great deal but are also spending much of their time with cell phones, tablets, computers, and video games, primarily indoors.

Intense periods of reading and studying were disproved as a cause of myopia during a study in 2000. Seven years later, scientists from Ohio State University followed more than 500 eight- and nine-year-olds with healthy vision and tracked the time they spent outdoors. After five years, 20 percent had developed myopia, which correlated to the time they spent indoors. This was confirmed one year later, when scientists in Australia studied 4,000 students and also reported that the amount of time spent indoors was the important factor.

It’s probably because the retina of the eye produces and releases more dopamine, a neurotransmitter, during the day to signal the eye to switch from night to daytime vision. Indoor light disrupts this cycle, affecting eye development. Only 30 percent of Australian children who spent three or more hours outside each day had myopia. A systematic review paper aggregated previous studies and concluded that each hour of each week spent outside reduces a child’s chance of developing myopia by 2 percent.

Researchers are examining possible ways to control the development of myopia, such as altering the way contact lenses focus light, producing eye drops that block neurotransmitter release, and using artificial lights like those used to treat seasonal affective disorder, also known as winter depression. Of course, having children play or simply be outside seems the best option, and it has other health benefits too.

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I Can See Again

By Medical Discovery News

Nov. 24, 2012


Blind mice don’t only exist in nursery rhymes, but in scientific laboratories. Scientists have been able to restore the vision of some such mice that were impaired by the same family of eye diseases that cause blindness in millions of Americans. The landmark study successfully transplanted immature photoreceptor cells, which are nerve cells in the retina responsible for sight.

Photoreceptor cells gradually die off in people with certain degenerative eye diseases. Once enough of the cells are gone, a person goes blind and no treatment can reverse the damage.

The research team from University College London Institute of Ophthalmology proved they can reverse the damage in adult mice with nonfunctioning rods. Rods and cones are the two types of photoreceptor nerve cells that make up the retina. These nerve cells convert light energy into signals that travel the optic nerve to the brain. Cones detect such things as color and detail and provide the center field of vision. Rods detect black and white and enable peripheral and low-light vision.

In the study, researchers took mice without functioning rods and injected their retinas with immature rod receptor cells from young, healthy mice. In four to six weeks, one in six of the mice with transplanted rod precursor cells seemed to be functioning nearly as well as mice with normal rod photoreceptors. These transplanted cells formed nerve connections resembling normal rod cells and generated signals that were transmitted to the brain for visual processing.  This is the first time that transplanted photoreceptor cells have been shown to integrate into the circuitry of the retina and improve vision.

To test their results, researchers placed treated mice and diseased mice into a dimly lit water maze. Recall the diseased mice do not have functioning rods, which means they can’t see in low light. If the transplant works, the mice with new rods should be able to spot a visual cue for a hidden platform and get out of the water. The mice with implants had no difficulty finding the platform and climbing out. The untreated, diseased mice took much longer and did a thorough search of the maze before finding the platform.

Researchers say the study’s success was due to the large number of photoreceptor cells they implanted – 200,000 compared to less than 1,000 cells in other studies. Next, researchers plan to test whether the procedure is as successful in transplanting precursor cones in mice.

A similar but separate study in humans is already undergoing clinical trials involving 12 patients with Stargardt disease, the most common form of inherited juvenile macular degeneration. By age 50, half are legally blind. The participants have been injected with 50,000 to 200,000 embryonic stem cells. The aim of these early clinical trials is to determine if the implant of embryonic stem cells is safe and well tolerated. So far, the trials are promising.

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