Myopia, or nearsightedness, is on the rise among both adults and children. We know that too much time in front of the computer can be to blame, but newer studies suggest time spent out in the sun may be an even more important factor. So how can we prevent or eventually correct myopia?
Hi I’m Dr. Sabrina Stierwalt, and I’m Everyday Einstein bringing you Quick and Dirty Tips to help you make sense of science.
Whenever I go to the optometrist, I dread the question, “How many hours a day do you typically spend at the computer?” Should I generously round down (read: lie) so as not to horrify her with my answer? The truth is, I spend a whopping 12 hours a day at my computer (or smartphone).
Doctors have suspected for a while that such extended small screen time could lead to nearsightedness, a condition where objects far away appear blurry. But new studies are showing that time spent out in the sun could also play a role.
So what really causes nearsightedness? Is myopia genetic? Can we prevent, or eventually correct, myopia?
Your Eye Is a Lens
When you view something, like the sunrise or your cup of coffee in the morning, your eye works much like a camera lens to gather and then focus the incoming light. When the light first reaches your eye and enters through your cornea, the clear front window to your eye, the light rays arrive at a range of angles.
The bend in your cornea then focuses that light or draws those light rays together so they are instead in a narrow beam that can then enter through a smaller hole, your pupil. This bending is called refraction.
Your iris, the colored part of your eye, acts like the camera’s shutter by opening and closing to let more or less light in through the pupil. Once the light passes through the lens, it is focused on a thin layer of nerve cells on the back of your eye, called your retina.
The nerve cells, called rods and cones because of their shapes, waiting on the retina interpret the incoming information (how bright or dim an object is, how near or far, what angle the light is approaching from, etc.) for the optic nerve which relays the information to your brain.
What Is Myopia?
For people who are nearsighted, or have difficulty seeing things that are far away, light rays passing through the eye’s lens fall short of reaching the back of the eye and instead get focused just in front of the retina. This can happen when the eyeball’s overall shape is elongated or when the cornea is too strongly curved.
People with normal visual acuity are said to have 20/20 vision, meaning they can see clearly and sharply something at 20 feet when that object is at a distance of 20 feet away. Someone with myopia may instead have 20/100 vision. They have to be 20 feet away from something that a person with normal vision could see clearly and sharply from a distance of 100 feet.
The American Optometric Association estimates that 30% (and rising!) of the population are nearsighted, making it a pretty common condition. Myopia can start in childhood and then continue to progress as our eyeballs continue to grow, usually until about the age of 20. Adults can also develop myopia later in life and eventually require the help of reading glasses.
For some people, having myopia only means having to put on glasses or contact lenses to watch a movie, see the chalkboard in school, or drive a car. For others, like my friend who has to put his glasses in the same spot every night before bed or else he won’t be able to see to find them in the morning, corrective lenses need to be worn all the time.
How Can We Correct Nearsightedness?
If your level of myopia is relatively low, you may choose to correct it with glasses or regular contact lenses. Both corrective lenses work the same way, by bending the light before it reaches your eye so that your eye is able to focus the light correctly.
Another non-surgical correction for myopia is corneal refractive therapy which works to reshape the cornea by wearing a series of rigid, corrective lenses. These lenses work much like braces do on your teeth and place pressure on the cornea to flatten it.
If you are not a fan of putting lenses in your eyes or have trouble keeping track of your glasses, there are surgical corrections for myopia that involve either implanting a corrective lens on top of the natural lens or by replacing the natural lens altogether. These surgeries are called refractive surgeries and are regularly used for patients with cataracts, or cloudy spots on their eyes (and thus in their vision).
Laser surgeries can also remove tiny amounts of tissue from the cornea in order to reshape it and thus change where it focuses incoming light. Many people who undergo laser surgery end up with perfect 20/20 vision afterward.
So what causes myopia?