Myopia is the medical name for nearsightedness. People with myopia have blurry vision at greater distances. This condition is a very common type of refractive error, affecting more than 30 percent of Americans. That figure is projected to rise significantly by the year 2050, according to the National Eye Institute.
Fortunately, there are safe and effective fixes, which fall into three categories: (1) corrective lenses, (2) surgery, and (3) therapy.
Myopia occurs when light focuses too far in front of the retina and not on the wall of the retina itself, where the light rays are received before being sent to the brain via the optic nerve. Most of the time, this happens because the shape of the eyeball is too long. Less commonly, myopia is a result of a misshapen lens or cornea.
Because the cause of most nearsightedness is an elongated eyeball, myopia is not considered “curable,” only “correctable.” No treatment exists to change the overall shape of the eyeball.
However, it is possible to reduce the increase of myopia over time, especially in young children whose eyes are still growing. As with many vision conditions, yearly eye exams and early intervention are key to successful treatment.
There are three types of interventions that are used to correct myopic vision.
- Corrective lenses - glasses and contacts.
- Surgery - LASIK, PRK, and the implantation of an artificial lens.
- Therapy - Ortho-k (or CRT) or eye exercises
First, we have corrective lenses for myopia.
Glasses are the safest and simplest way to correct nearsightedness. It is also the primary way that Americans choose to treat myopia. Eyeglasses can be worn for only those activities in which they are needed for better vision at greater distances, such as driving, watching movies, or seeing the board at the front of a classroom.
Besides how easy glasses are to remove when they're not needed, they also have the advantage of being able to treat several issues at once.
Most people start out with a single-lens eyeglass, but “patients over age 40, or children and adults whose myopia is due to the stress of near-vision work, may need a bifocal or progressive addition lens. These multifocal lenses provide different powers or strengths throughout the lens to allow for clear vision in the distance and up close,” according to the American Optometric Association. Improvements in technology have made even these multifocal lenses lighter more durable than ever before.
Contact lenses have been a viable alternative to eyeglasses for almost a century.
Although scientists as early as da Vinci and Descartes came up with designs for contact lenses, the idea wasn’t practical until the invention and widespread manufacture of plexiglass in the 1930s. Since then, they have improved to allow more oxygen to reach the eye and to be thinner, more powerful, and more comfortable. They even allow for a wider field of vision than glasses. Contacts also have the advantage of allowing wearers to add sunglasses or goggles on top, and of being safer during high-contact sports and other physical activities.
However, contact lenses are not right for everyone, including those with some eye diseases. They also require precise handling and care to ensure they’re clean and safe in the eye. An optometrist needs to fit them carefully to ensure comfort and safety, and annual visits to an eye care professional are necessary.
Moving along to surgical methods, laser-assisted in situ keratomileusis is a surgical procedure that permanently corrects nearsightedness by using a laser to change the shape of the cornea—the clear covering of the front of the eye.
The FDA describes the process that starts with the laser acting as a blade to cut a flap in the cornea. Then, “a hinge is left at one end of this flap. The flap is folded back revealing the stroma, the middle section of the cornea. Pulses from a computer-controlled laser vaporize a portion of the stroma and the flap is replaced.” Then the cornea heals, and refractive vision is permanently improved so that patients have little to no reliance on glasses or contacts.
Photorefractive keratectomy is another type of laser surgery to correct refractive errors. Like LASIK, the degree of vision correction “is limited by the amount of corneal tissue that can be safely removed,” according to the AOA. Whereas LASIK removes tissue from the center of the cornea, PRK removes a thin layer of tissue from the surface of the cornea.
Other, non-laser refractive surgery procedures may be indicated for patients with more severe myopia or those who have very thin corneas. This kind of surgery involves implanting artificial lenses just in front of the natural lens or even in place of the natural lens. The artificial lens is made with the refractive correction necessary to improve the patient’s myopia. This procedure is actually very similar to cataract surgery because they both involve implantation of an artificial lens.
Finally, we come to vision therapy.
Corneal refractive therapy, also known as orthokeratology, is a non-surgical option for treating moderate myopia.
In CRT, patients wear rigid contact lenses that put pressure on the cornea in order to flatten it gradually. These lenses reshape the cornea’s curvature in small, incremental steps, so patients must progress through a series of increasingly corrective lenses. The lenses are worn for limited periods of the day or night and then removed, at which time the patient’s vision is temporarily corrected.
Vision therapy can help patients who suffer from stress-related muscle spasms of that control eye focusing, as well as other causes of myopia. Only an optometrist or ophthalmologist can determine if a particular patient is a good candidate for vision therapy. Prescribed exercises may involve the use of prisms, computer-based activities, visual aids, and eye exercises. The therapy has several benefits, including:
- strengthening the coordination between visual and neurological systems
- improving communication between the eyes
- building up the muscles that may otherwise cause further progression of myopia
- developing ocular strength and function
The rates of myopia vary widely by country, race, and socioeconomic class. Exciting new research points at a previously unrecognized factor in preventing nearsightedness—time spent outdoors. It is thought that there is a correlation between the hours that children experience direct sunlight outdoors and lower rates of myopia.
Luckily, treatments like corrective lenses, surgery, and therapy are able to provide safe and effective vision correction for millions of Americans.