 |
What is Nearsightedness?
Nearsightedness or myopia causes blurry vision when looking at distant objects such as a blackboard at school. Myopia may also cause eyestrain, headaches, and lead to squinting to be able to see properly.
How important is myopia?
In the U.S. and Europe approximately 30% to 40% of adults in the U.S. and up to 80% to 90% of the Asian young adult population is myopic. One estimate is that this proportion of those with myopia in the US might increase to almost 60% by 2050. The annual direct cost of myopia was estimated to have reached roughly $6.6 billion in 2022.
Myopia causes the inconvenience and problems associated with poor vision in day to day living and hampers activities such as schoolwork, sports and driving. In addition, depending on its severity, myopia increases the risk of serious sight-threatening complications, such as myopic macular degeneration (myopic maculopathy), retinal detachment, glaucoma, and cataracts. For every 1.00 Diopter of myopia, the chance of having myopic maculopathy increases by 67%.
What causes myopia?
Myopia occurs when the light entering the eye is not focused properly. When the cornea is too curved or the eye is longer front to back than normal, or both conditions are present, light is focused in front of the retina instead of on the retina and vision is blurry.
The causes of myopia are complex and not fully understood. Genetics is one factor. If a parent is myopic it increases the odds that their children will be. Other factors that are associate with increased risk are the amount of time spent doing close work and the amount of time spent indoors without exposure to natural light.
When and how is myopia diagnosed?
Some kids are born myopic, but the onset of myopia is typically at approximately 8 years of age and progresses until 15 or 16 years of age. Myopia is often discovered in children when they are between ages 5 and 12 years old but some children do not become myopic until their teens. During the teenage years of rapid bodily growth, myopia may become worse. There is usually little change between the ages of 20 and 40. The younger the age at which myopia first develops the greater the final severity of myopia as an adult.
Regular eye exams are indicated because young children with myopia might not complain about their blurry vision. The usual way to diagnose myopia is reading the eye chart on a machine called a phoropter. If a patient is too young to read the letters on an eye chart, an ophthalmologist can diagnose the myopia with a retinoscope.
Can the progression of myopia be slowed or prevented?
Myopia cannot be reversed, so the goal of treatment is to keep it from developing or from getting worse.
The best predictor of whether a child with normal vision will later develop myopia is their eye prescription and their age. Prescribing a treatment to those children most at risk before the onset of myopia may have a greater effect than slowing myopia progression after onset because it provides earlier intervention when eye growth and progression are fastest.
The long-term effectiveness existing treatments to prevent or delay the onset of myopia is uncertain but delaying the age of myopia onset has the potential to reduce how myopic the person becomes. However, this is yet to be fully confirmed by long-term studies.
Patients with lower degrees of myopia have better vision when not wearing corrective lenses, are better candidates for refractive surgery to correct their vision and are at lower risk of sight-threatening eye conditions.
- Spend time in natural light. Evidence suggests that children who spend more time outdoors are less likely to be, or to become myopic, irrespective of how much near work they do, or whether their parents are myopic.
In one study an additional 40-minute class of outdoor activities was added to each school day, and parents were encouraged to engage their children in outdoor activities after school hours, especially during weekends and holidays. After 3 years, the cumulative incidence rate of myopia was 30.4% in the intervention group 39.5% in the control group schools where children and parents continued their usual pattern of activity.
- Always wear prescription reading glasses when viewing anything within an arm’s length or closer. This includes computers and tablets.
- Viewing distance should never be closer than the distance from your elbow to your fist when your fist is placed on your chin.
- Insure good lighting when reading, using the computer and watching TV. Dark rooms are not a good idea.
- Use two light sources when reading; a room light and a direct light on the page or task.
- Avoid close viewing for extended periods of time. This includes computer work, video games, and reading. After every page or 5 minutes spent looking at a page or screen, remember to look out a window and defocus.
- Give your eyes a break. Children should have a break every 15 minutes. 30 minutes is recommended for teenagers.
There is no scientific evidence to suggest that eye exercises, vitamins or supplements can prevent or cure myopia.
Atropine eye-drops to slow progression of myopia.
Daily use of low-dose atropine eye drops at bedtime slows the progression of myopia in children and teenagers. By starting early, for most kids — about 90%— their rate of myopia progression decreases or slows by about half. The sooner they start atropine eye drops, the less nearsighted they will be overall.
In one study of children aged 4 to 9 years without myopia, nightly use of 0.05% atropine eyedrops over 2 years resulted in a rate of new cases of myopia of 28.4% and 53.0% for the untreated placebo group. Similarly, only 25.0% of children in the 0.05% atropine group compared to 53.9% of children in the placebo group experienced fast myopic shift.
It is not yet known whether delaying the onset of myopia will reduce the final degree of myopia as an adult or whether it simply postpones the typical myopia progression to later years and thus does not decrease the long-term risk associated with higher degrees of myopia.
Side effects of atropine drops at low doses may include intolerance to light (photophobia) and redness or itchiness around the eye.
Contact lenses to slow progression of myopia.
Peripheral defocus contact lenses are special contacts made for children 6 to 12 years of age with myopia. These lenses have different areas of focus. The center of the lens corrects blurry distance vision, while the outer parts of the lens blur the child’s peripheral (side) vision. Blurring side vision is thought to slow eye growth and limit myopia.
One study using commercially available soft multifocal contact lenses found a 43% slowing of myopia progression and 36% slowing of eye growth. Other similar studies report a change in myopia progression that ranged from an increase of 10% to a decrease of 79%.
Soft multifocal contact lenses may help certain children but might not work for all children. Studies with follow-up of only to 3 years, do not provide evidence about whether the effects will persist through adulthood to reduce the development of vision-threatening pathologic myopia or whether discontinuation of the lenses results in loss of their beneficial effects.
As described below, like any contact lens, it is important to correctly wear, clean, and store the lenses to avoid getting a corneal infection.
Glasses to slow myopia.
Recent studies with novel spectacle lenses with aspherical lenslets have been tested for myopia control efficacy. Preliminary results showed that over 2 years of wear, spectacle lenses with highly aspherical lenslets and spectacle lenses with slightly aspherical lenslets were effective in slowing myopia progression. A dose-dependent response was observed, as use of highly aspherical lenslets had significantly better myopia control effect than slightly aspherical lenslets.
Although additional research is needed before recommending highly aspherical lenslet spectacles for routine use in childhood, the results of this study are promising.
Eyeglasses and contact lenses
Wearing glasses or contact lenses is the usual way to correct myopia. They help the wearer to have clear vision by focusing light on the retina.
There are two main types of eyeglasses. Single-vision glasses have an all-purpose lens designed to help either close up or far vision. They are often prescribed for myopia. Multifocal glasses have bi-focal or tri-focal lenses. They correct both near and distance vision with the same lens. One portion is focused for distance vision, while the other portions are used for closer activities such as reading. Progressive lenses have a smooth transition instead of visible dividing lines between distance and near focal areas. Progressive lenses require time to get used to and can cause more distortion than other types of lenses, making them difficult to wear for some people. Computer glasses have multifocal lenses with a correction specifically designed for focusing on computer screens which are usually positioned about 20 to 26 inches away.
Contact lenses
Contact lenses are thin, clear plastic disks worn in the eye to improve vision. Contacts float on the tear film that covers the cornea. Like eyeglasses, contact lenses can improve vision for people with myopia and other refractive errors.
Types of Contact Lenses
Contacts are made from many kinds of plastic. The two most common types of contact lenses are hard and soft. The most common type of hard contact has a rigid gas-permeable lens. They hold their shape, yet they let oxygen flow through the lens to your eye. Most people choose to wear soft contact lenses. This is because they tend to be more comfortable and there are many options.
Types of Soft Lenses
Daily wear contacts. These are worn when awake and removed for sleep. Many are disposable, meaning that you wear a new pair each day. Others are designed for replacement after longer periods of use up to a month.
Extended wear contacts. They can be worn while asleep, but they need to be removed for cleaning at least once a week. Fewer ophthalmologists recommend these contacts because they increase the chance of getting a serious eye infection.
Toric contacts. These can correct vision for people with astigmatism, though not as well as hard contact lenses. Toric lenses can be for daily or extended wear.
Colored (tinted) contacts. Vision-correcting contact lenses can be tinted to change the color of your eye. They are available for daily wear, extended wear, and with toric lenses.
Decorative (cosmetic) contacts. These lenses change the look of your eye but do not correct vision. To avoid getting dangerous eye infections these lenses must be treated like prescription contacts. This means cleaning them regularly and thoroughly as directed. Make sure your contact lenses are doctor recommended, medically safe and FDA-approved. Non-prescription costume contacts can cause cuts, sores, eye infections, pain, a need for surgery or even blindness.
Other types of contact lenses include Contacts for presbyopia. They are designed to correct the normal vision problems people get after age 40, when it becomes harder to see close objects clearly. Hybrid contact lenses. These lenses have a rigid center surrounded by a soft outer ring. It combines the sharp vision of a hard lens with the comfort of a soft lens. Scleral contact lenses. These gas permeable (GP) lenses stretch over the cornea and rest on the sclera (white part) of the eye.
You can get a serious eye infection if you do not clean, disinfect and store your contact lenses correctly. You must clean and disinfect any contact lens you remove from your eye before you put the lens back in. Always follow your eye care provider's instructions exactly.
Remove your contact lenses and call your eye doctor right away if your eyes are very watery or sensitive to light. Do the same if you have blurry vision or notice discharge (ooze or pus) coming from your eye. These can be symptoms of serious eye problems.
To safely wear contact lenses, you must be committed to caring for them properly and replacing them when needed. Talk with your ophthalmologist or other eye care professional to discuss your vision needs and expectations. Some people are not appropriate candidates for contacts because of eye conditions or conditions like dust where they work. An eye care professional can help you decide if contacts are a good option for you.
Orthokeratology (ortho-k) to treat myopia
Ortho-K corneal reshaping hard contact lenses are worn at night to temporarily flatten the cornea and reduce myopia. When the lenses are removed in the morning, the reshaped cornea provides clear vision all day without the need of glasses or contact lenses.
Wearing Ortho-K lenses only improves vision for a short time. Once you stop wearing the lenses, the cornea slowly goes back to its normal shape and myopia comes back. Still, ortho-K may provide some permanent reduction in myopia progression.
Patients must sleep in hard contact lenses every night. There is a risk of serious, vision-threatening eye infections with Ortho-K lenses. They are also more difficult to fit compared to regular contacts lenses, and more follow-up doctor visits are needed.
Refractive surgery to treat myopia
These surgical procedures should be undertaken only after careful consideration by a patient and thorough evaluation by an ophthalmologist. They are not appropriate for children. The American Academy of Ophthalmology lists a series of questions that should be addressed prior to choosing LASIK at Questions to Ask When Considering LASIK. The Academy partnered with the U.S. Food and Drug Administration in 2008 to produce a free PDF: Is LASIK For Me? A Patient’s Guide to Refractive Surgery.
LASIK and similar procedures to treat myopia
LASIK surgery uses either a microkeratome or a laser to reshapes a patients cornea using a laser. Similar surgical procedures are carried out in Epi-LASIK, Photorefractive keratectomy (PRK), and small incision lenticule extraction (SMILE)––a newer type of laser refractive surgery.
Like any surgery, these procedures may cause eye discomfort, inflammation, infection, and end up causing sensitivity to light, glare and halos around lights, poor night vision, and blurry vision. Most but sometimes not all side effects and complications resolve over time or can be treated without any loss of vision. However, very rare problems may include worse vision than prior to the surgery and blindness.
Also, with LASIK, your vision may end up being under-corrected or over-corrected. These problems often can be improved with glasses, contact lenses, or additional laser surgery.
Phakic Intraocular Lenses (IOLs) to treat myopia
Phakic IOLs are designed for people with high degrees of refractive errors that cannot be safely corrected with corneal-based refractive surgery. The phakic IOL, sometimes referred to as an implantable contact lens, or ICL, is surgically implanted inside the eye in front of the eye's natural lens. The eye's natural lens is not removed, so patients can retain their pre-existing ability to focus.
During the phakic IOL procedure, your ophthalmologist places the phakic IOL either in front of or behind the iris of the eye. Once the IOL is properly positioned inside the eye, it provides the necessary correction to redirect light rays precisely onto the retina.
Refractive Lens Exchange (Clear Lens Extraction) to treat myopia
With refractive lens exchange (RLE) — also called Clear Lens Extraction or CLE — an artificial lens is used to replace your eye's natural lens in order to improve vision. The procedure is performed much like cataract surgery.
As in cataract surgery, RLE may employ multifocal or accommodative intraocular lenses (IOLs). These lenses allow the ability to focus at all distances. In refractive lens exchange an ophthalmologist removes the natural lens inside your eye and replaces it with an artificial lens that better focuses light on the retina.
As with LASIK, these types of refractive surgery carry risks of complications and side effects including eye discomfort, inflammation, infection, and may end up causing sensitivity to light, glare and halos around lights, worse night vision and blurry vision.
Since phakic Intraocular Lenses and refractive lens exchange require surgery within the eye, like with cataract surgery risks include bleeding, damage to the retina, retinal detachment, and dislocation of the IOL implant. Most but sometimes not all side effects and complications resolve over time or can be treated without any loss of vision. However, rare problems may include worse vision than prior to the surgery and blindness.
If you are happy wearing contacts or glasses, you may not want to have refractive surgery. Together, you and your ophthalmologist can weigh the risks and rewards of LASIK and other refractive surgeries. So talk with your ophthalmologist about your vision needs and expectations. Together you can explore options for achieving better vision.
Sources of additional Information
American Academy of Ophthalmology. https://www.aao.org/eye-health/diseases/myopia-nearsightedness
Berntsen DA, Walline JJ. Delaying the Onset of Nearsightedness. JAMA. 2023;329(6):465–466. doi:10.1001/jama.2022.24386
Yam JC, Zhang XJ, Zhang Y, et al. Effect of low-concentration atropine eyedrops vs placebo on myopia incidence in children. JAMA. Published February 14, 2023. doi:10.1001/jama.2022.24162
Musch DC, Archer SM. Clinical Relevance of Myopia Control With Specialized Spectacles. JAMA Ophthalmol. 2022;140(5):478–479. doi:10.1001/jamaophthalmol.2022.0533
Bao J, Huang Y, Li X, et al. Spectacle lenses with aspherical lenslets for myopia control vs single-vision spectacle lenses: a randomized clinical trial. JAMA Ophthalmol. Published online March 31, 2022. doi:10.1001/jamaophthalmol.2022.0401
Repka MX. Prevention of Myopia in Children. JAMA. 2015;314(11):1137–1139. doi:10.1001/jama.2015.10723
He M, Xiang F, Zeng Y, et al. Effect of Time Spent Outdoors at School on the Development of Myopia Among Children in China: A Randomized Clinical Trial. JAMA. 2015;314(11):1142–1148. doi:10.1001/jama.2015.10803
Walline JJ, Walker MK, Mutti DO, et al. Effect of High Add Power, Medium Add Power, or Single-Vision Contact Lenses on Myopia Progression in Children: The BLINK Randomized Clinical Trial. JAMA. 2020;324(6):571–580. doi:10.1001/jama.2020.10834
| |
|
|
