Myopia, commonly known as nearsightedness, occurs when the focal point for light entering the eye is located in front of the retina, the light-sensitive tissue located on the back of the eyeball near the optic nerve.   

So what physical conditions cause myopia?

The first is the growth of the eye. If the eye grows longer than a normal eye’s shape, that will cause the focal point of the eye to be located in front of the retina. Many doctors believe this cause of myopia is hereditary, because the risk of myopia in a patient increases when one or both of their parents also have myopia.

The cornea can also cause myopia. The cornea, the transparent surface of your eye, has to have a specific curve for the focus to hit the retina, even if the eye grows to the normal length. If the curve of the retina is too flat or too sharp, it will cause the focus to shift away from the focal point on the retina that allows clear vision.

Aside from hereditary factors, doctors also believe that you can develop myopia if you do a large number of tasks that bring items close to your face. These tasks can include things like reading a book or a smartphone, viewing a video on a smaller electronic device, or any task that requires you to focus on extremely small print or other materials for an extended period of time. While there has not been a study conclusively proving that these factors cause myopia, doctors have been able to prove that eye-strain can cause problems with vision. 

A recent study has shown that spending too much time indoors can help develop and increase myopia in children. Dr. Kathryn Rose of the University of Sydney’s Faculty of Health Sciences told CNN that spending 10-14 hours outside beyond the hours of a normal school day could show a benefit in the prevention of myopia. The study also showed that only three to six hours of sunlight above the length of a school day would have no effect. The study further showed that it didn’t matter if the children wore sunglasses to protect their eyes from UV rays as long as the time period ranged between 10 and 14 hours.

In some very rare cases, myopia can be caused by infections in the eye. While most infections can be treated with antibiotics before major damage occurs to the eye, retinal damage from an infection could result in permanent myopia. Infections can also cause subtle changes to the shape of the cornea, leading to myopia. Again, these situations are considered rare, and most eye infections will not result in long-term myopia.

There are also forms of temporary myopia related to time of day or medical conditions.  “Night” myopia takes place when people have blurred distance vision at night. When in the dark, the eye is not receiving enough light to focus, or too much light comes from the sides rather than from in front of the eye. “False” myopia happens when you are intensely focused on some object or text directly in front of the eye for an extended period of time and then look toward distant objects. This usually clears up after some rest. Finally, myopia symptoms could signal variations in blood sugar levels for people who suffer from diabetes.

Should you find yourself having trouble seeing objects at a distance, it’s important to contact your doctor for an examination. EyeCare 20/20 offers comprehensive vision-care services, and we invite you to contact us promptly for all your eye-health needs.

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