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Nearsightedness (Myopia)
Nearsightedness, or myopia, as it is medically termed, is a vision condition in which close objects are seen clearly, but objects farther away appear blurred. Nearsightedness exists if the eyeball is too long or the cornea (the clear front cover of the eye) is too curved. As a result, light entering the eye isn’t focused correctly which results in blurred vision.
No. Nearsightedness is a very common vision condition affecting nearly 30 percent of the U.S. population.
The exact cause of nearsightedness is unknown, but two factors are believed to be primarily responsible for its development – heredity and visual stress from overwork and environmental factors. Nearsightedness may also occur due to health problems.
There is significant evidence that many people inherit nearsightedness, or at least the tendency to develop nearsightedness. If one or both parents are nearsighted, there is an increased chance their children will be nearsighted.
There is growing evidence that nearsightedness is influenced by visual stress. Even though the tendency to develop nearsightedness may be inherited, its actual development may be affected by how a person uses their eyes.
Individuals who spend considerable time reading, working at a computer, or doing other intense close visual work may be more likely to develop nearsightedness.
People who do an excessive amount of near vision work may experience a false or “pseudo” myopia. Their blurred distance vision is caused by over use of the eyes’ focusing mechanism. After long periods of near work, their eyes are unable to refocus to see clearly in the distance. The symptoms are usually temporary and clear distance vision may return after resting the eyes. However, over time constant visual stress may lead to permanent damage and reduction in distance vision.
Some people may experience blurred distance vision only at night. This “night myopia” may be due to the low level of light making it difficult for the eyes to focus properly or the increased pupil size during dark conditions, allowing more peripheral, unfocused light rays to enter the eye.
Generally, nearsightedness first occurs in school-age children. Because the eye continues to grow during childhood, it typically progresses until about age 20. However, when nearsightedness develops in adults it is typically due to visual stress or a health condition, such as diabetes. Symptoms of myopia may indicate variations of blood sugar levels in people with diabetes or may be an early indication of a developing cataract.
People with myopia can have difficulty clearly seeing a movie or TV screen, a whiteboard in school, or while driving.
Testing for myopia may use several procedures to measure how the eyes focus light and to determine the power of any optical lenses needed to correct the reduced vision. As part of the testing, you will identify letters on a distance chart. This test measures visual acuity, which is written as a fraction, such as 20/40. The top number of the fraction is the standard distance at which testing is performed (20 feet). The bottom number is the smallest letter size read. A person with 20/40 visual acuity would have to get within 20 feet to identify a letter that could be seen clearly at 40 feet in a “normal” eye. Normal distance visual acuity is 20/20, although many people have 20/15 (better) vision.
Using an instrument called a phoropter, Dr. Craig places a series of lenses in front of your eyes and measures how they focus light using a handheld lighted instrument called a retinoscope. Or the doctor may choose to use an automated instrument that evaluates the focusing power of the eye. The power is then refined based on your responses to determine the lenses that allow the clearest vision. Your doctor can conduct this testing without using eye drops to determine how the eyes respond under normal seeing conditions.
In some cases, such as for patients who can’t respond verbally or when some of the eye’s focusing power may be hidden, a doctor may use eye drops. The eye drops temporarily keep the eyes from changing focus during testing. Using the information from these tests, along with the results of other tests of eye focusing and eye teaming, your doctor can determine if you have myopia. They will also determine the power of any lens correction needed to provide a clearer vision. Once testing is complete, your doctor can discuss treatment options.
People with myopia have a variety of options to correct vision problems. Dr. Craig will help select the treatment that best meets the visual and lifestyle needs of the patient.
Dr. Craig can prescribe corrective lenses that correct nearsightedness by bending the visual images that enter the eyes, focusing the images correctly at the back of the eye.
For most people with myopia, eyeglasses are the primary choice for correction. Depending on the amount of myopia, you may only need to wear glasses for certain activities, like watching a movie or driving a car. Or, if you are very nearsighted, you may need to wear them all the time. Generally, a single-vision lens is prescribed to provide clear vision at all distances. However, 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.
For some individuals, contact lenses offer clearer vision and a wider field of view than eyeglasses. However, since contact lenses are worn directly on the eyes, they require proper evaluation and care to safeguard eye health.
Another option for treating nearsightedness is orthokeratology (ortho-k), also known as corneal refractive therapy (CRT). In this nonsurgical procedure, you wear a series of specially designed rigid contact lenses to gradually reshape the curvature of your cornea, the front outer surface of the eye. The lenses place pressure on the cornea to flatten it. This changes how light entering the eye is focused. You wear the contact lenses for limited periods, such as overnight, and then remove them. People with mild myopia may be able to temporarily obtain clear vision for most of their daily activities.
Laser procedures such as laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) are also a possible treatment for nearsightedness in adults. A laser beam of light reshapes the cornea by removing a small amount of corneal tissue. The amount of myopia that PRK or LASIK can correct is limited by the amount of corneal tissue that can be safely removed. In PRK, a laser removes a thin layer of tissue from the surface of the cornea in order to change its shape and refocus light entering the eye. LASIK removes tissue from the inner layers, but not from the surface, of the cornea. To do this, a section of the outer corneal surface is lifted and folded back to expose the inner tissue. A laser then removes the precise amount of corneal tissue needed to reshape the eye. Then, the flap of outer tissue is placed back in position to heal.
For people with higher levels of nearsightedness, or whose corneas are too thin for laser procedures, may be able to have their myopia surgically corrected. These procedures involve implanting a small lens with the desired optical correction directly inside the eye, either just in front of the natural lens (phakic intraocular lens implant) or replacing the natural lens (clear lens extraction with intraocular lens implantation). This clear lens extraction procedure is similar to cataract surgery but occurs before a cataract is present.
Vision therapy is an option for people whose blurred distance vision is caused by a spasm of the muscles that control eye focusing. Various eye exercises can improve poor eye focusing ability and regain clear distance vision.
Children who are at high risk of progressive myopia (family history, early age of onset, and extended periods of near work) may benefit from treatment options that have been shown to reduce the progression of myopia. These treatments include the prescription of bifocal spectacle or contact lenses, orthokeratology, eye drops, or a combination of these. Because persons with high myopia are at a greater risk of developing cataracts, glaucoma, and myopic macular degeneration, myopia management may help preserve eye health.
You deserve the best possible eyesight. Get the crispest, clearest vision by scheduling a comprehensive eye exam at Family Eye Care Center in Elkins, WV. We offer diagnostic testing, corrective lenses and myopia management for you and family members of all ages from birth onward. To learn more and schedule an appointment, call: (304) 636-9111.
Much of the educational information provided on this page has been adapted with permission from copyrighted resources provided courtesy of American Optometric Association (AOA) for use by its members. AOA is the leading authority on quality eye health and vision care, representing doctors of optometry and optometric professionals throughout the United States.
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