What Is Myopia?
Myopia, also called nearsightedness, is a vision condition in which you have difficulty seeing far away.
Myopia is one form of refractive error. When you have a refractive error, your eyes do not focus images properly onto your retina, causing you to see blurry. The retina is the tissue lining the back of your eye.
There are three types of refractive errors:
- Myopia (nearsightedness) is when your eye focuses images in front of the retina, causing blurry vision at a distance.
- Hyperopia (farsightedness) is when your eye focuses images behind the retina, causing blurry vision up close.
- Astigmatism is when your eye focuses images at more than one point. Some images may focus in front of your retina, and some behind the retina. Astigmatism causes you to see blurry up close and far away.
It is possible to have a combination of refractive errors. As an example, you can have myopia and astigmatism in the same eye. You can also have different refractive errors between each eye, such as hyperopia in one eye and myopia in the other.
Studies estimate that over 40 percent of people in the United States have myopia.
Causes of Myopia
Myopia occurs when the focusing power of your eye is too strong. This causes images to focus in front of your retina. There are two ways this can happen:
- You have a longer eyeball length than average.
- Your cornea, which is the clear covering in front of your eye, is too steep.
The genetics of myopia is complex. Research shows that myopia and other refractive errors have a multifactorial inheritance. This means multiple genes influence whether or not you will develop myopia. Multifactorial conditions such as myopia tend to run in families.
Myopia is also influenced by external factors such as lifestyle. Some research shows a positive relationship between myopia and higher amounts of near work activities, such as reading or computer work.
Other studies found a negative relationship between myopia and outdoor activities. The theory is that exposure to sunlight can slow down the progression of nearsightedness. For these reasons, eye doctors are recommending that young patients spend less time looking at digital devices and more time enjoying the outdoors.
Symptoms of Nearsightedness
General symptoms of nearsightedness include blurry vision at a distance, squinting, eye strain, and headaches.
Your symptoms may vary depending on how strong your prescription is. For reference, diopters (D) are the units your eye doctor uses to measure your prescription. We can divide myopia into different categories:
- Low myopia is -3.00 D or less.
- Moderate myopia ranges between -3.25 to -6.00 D.
- Severe myopia is anything above -6.00 D.
Generally, patients with low myopia only need to wear glasses to see far away. They do not need to wear glasses for near activities.
Patients with moderate to severe myopia generally need to wear glasses full-time, since they can only see objects that are very close to their face.
Nearsighted patients over 40 will notice that they cannot see up close while wearing their glasses. Your eyes lose the ability to focus at near with age, a process called presbyopia. These patients will remove their glasses to read. As an alternative, they may choose to use bifocal or progressive eyeglasses.
High myopia not only affects your ability to see but can increase your risk for certain eye diseases. These conditions include cataracts, glaucoma, retinal holes or tears, and retinal detachments.
How to Correct Myopia
The most common treatment for myopia is either glasses or contact lenses. If you prefer not to wear corrective lenses, there are other ways to treat myopia:
Orthokeratology lenses are hard, gas permeable contact lenses you use overnight. The lenses temporarily reshape your corneas while you are sleeping. After removing the contacts in the morning, you can see reasonably well for the day, without any glasses. Your corneas will start returning to their original shape after a day or two, so you will need to use the lenses every night.
Refractive Lens Exchange
This procedure removes the natural lens in your eye, which is very similar to cataract surgery. The surgeon implants an artificial lens that corrects your myopia. This surgery is an ideal option for patients with high myopia and who may develop cataracts soon. With a refractive lens exchange, you will not need cataract surgery later in life.
Phakic Intraocular Lens Implant
The main difference between this procedure and a refractive lens exchange is that your natural lens stays in place. Instead, the surgeon will place an artificial lens in front of your natural lens, which is called a posterior chamber phakic lens. Or, the surgeon may choose an anterior chamber phakic lens, which is an implant placed in front of the iris. This surgery is an excellent option for high myopia. Currently, it is not FDA-approved for other refractive errors such as hyperopia.
Laser Refractive Surgery
PRK and LASIK are excellent options for patients with myopia. Laser eye surgery is FDA approved to treat up to -12.00 D of myopia. In some cases, if your prescription is high and your corneas are too thin, you may not be eligible for laser eye surgery. Instead, your surgeon may perform a refractive lens exchange or phakic intraocular lens implant procedure.
Myopia control refers to treatments geared towards slowing down the progression of nearsightedness in children. Parents who are concerned about their children’s eyesight worsening at a rapid rate may seek myopia control options.
Other forms of treatment include:
- Orthokeratology (ortho-k). Multiple studies suggest that using these overnight lenses slow down the progression of myopia, versus wearing eyeglasses alone.
- Atropine eye drops. These eye drops temporarily relax the eye muscles that are responsible for focusing your vision. The idea is to reduce eye muscle fatigue that may lead to increased myopia. While this treatment can be very effective at slowing down myopia progression, there are some side effects. Atropine dilates your pupils, which causes light sensitivity, discomfort, and blurry vision at near. Children receiving atropine therapy will need to wear sunglasses outdoors and bifocal or reading glasses when viewing up close.
- Multifocal contacts. These contacts have both distance and reading prescriptions in them. Similar to atropine therapy, the idea behind multifocal contacts is to reduce eye muscle fatigue when reading. In studies, multifocal contact lenses slowed myopia progression by about 50 percent.
- Bifocal or progressive glasses. Multifocal glasses also help the eye muscles relax when performing near activities. Research shows these lenses are more effective at slowing down nearsighted progression versus single vision glasses alone.