Myopia, commonly referred to as nearsightedness, is an eye condition where the focal point of the eye is closer than optical infinity. In other words, things far away are blurry and things closer are clearer. It is corrected optically with eyeglasses, contact lenses, or refractive laser surgery. Myopia typically onsets in childhood or adolescence and occurs when the eye grows too long. The eye often continues to grow and the refractive error worsens (myopia progresses) so stronger optical correction is required. The progression usually slows down or plateaus on its own as the child gets older – some in their teenage years, some not until early or mid twenties. The lengthening of the eye secondary to myopia can result in, or increase the risk of, several serious eye health conditions as the patient grows older. The most notable eye diseases associated with myopia are retinal detachment, myopic macular degeneration, and glaucoma.
Nearly 30% of the Canadian population is myopic. In the United States, over the period of ~1971-2001, myopia increased by approximately 66%. This trend is expected to continue and nearly 50% of people worldwide are predicted to be myopic by 2050. Despite many years of research, the exact cause(s) of myopia are unknown. However, there are several theories.
Risk Factors
Family history is certainly a risk factor and certain genes have been identified as increasing the risk of becoming myopic. Having one myopic parent increases the risk of myopia compared to neither parent being myopic, and when both parents are myopic the risk increases even more. However, genetics alone does not explain the increased prevalence of myopia.
As discussed above, the eye lengthens with myopia progression. However, the central part of the back of the eye lengthens faster than the peripheral retina. Wearing conventional optical correction causes hyperopia (farsightedness) in the periphery, and this seems to contribute to myopia progression. Several optical correction options work on this basis to create a peripheral de-focus to slow myopia progression, as will be discussed below. This peripheral hyperopia is not the only cause of myopia progression. Studies have shown undercorrecting myopic refractive error can actually make it progress faster than full optical correction.
Several studies have shown when children spend more time outside, their risk of becoming myopic decreases. The current recommendation for children is to spend two hours outside daily; it doesn’t have to be all at once! It is currently unknown why more time outside reduces the chance of myopia, but some researchers theorize it is the brightness of the outdoors compared to our indoor environment. With that being said, sunglasses are still recommended for everyone when outside during the day to protect from the sun’s harmful rays. Wearing sunglasses while outside continues to offer the protective benefit against developing myopia. More recent studies have shown that once a child develops myopia, increasing time outside doesn’t slow the progression of myopia like it was once thought. Fortunately, there are several options for slowing down myopia progression in children.
Soft Contact Lenses
Health Canada approved MiSight soft contact lenses by Coopervision in 2018. These are lenses made from a hydrogel material (omafilcon A) and are daily disposables – the patient wears a new lens every day. They have a special optical design that allows light to be focused on the central retina (the macula) for clear central vision, and the light landing on the peripheral retina remains in front of the retina rather than behind it (causing peripheral de-focus, as described above). These lenses have been shown to reduce myopic progression on average by 59%. Understandably, many parents are hesitant about their young children wearing contact lenses for a variety of reasons. The initial three year study on children aged 8-14 found they did well with insertion and removal of the contact lenses. Furthermore, they reported the contacts were well-tolerated (comfortable) and provided excellent vision. No major complications were reported during the study’s period. It is important to remember that contact lenses are a medical device and require diligent care and follow up with your optometrist to prevent serious complications.
Spectacle Lenses
During the summer of 2020, ophthalmic lens company Hoya released MiYOSMART, the first commercially-available spectacle lens proven to significantly reduce the progression of myopia in children. These lenses use a special design known as DIMS (Defocus Incorporated Multiple Segments) that creates peripheral de-focus in a similar manner to the MiSight contact lenses. MiYOSMART was also shown to reduce myopic progression on average by 59%. Due to the special lens design, careful measurements by a professional during the spectacle fitting are crucial to minimize the time it takes for a child to adapt to wearing this new technology. After a small adaptation period (typically a couple of days to weeks), these lenses are well-tolerated and provide excellent vision.
Low-Dose Atropine Drops
Atropine drops have a long history with eye care. Eye drops containing similar drugs are commonly used to dilate the pupil during an eye exam to thoroughly examine the health of the eyes. These drops can also be used for cycloplegia, which inhibits the eye’s ability to focus at near, in order to accurately measure a person’s (often a child’s) eyeglass prescription. Typically, atropine is available in a 0.5% or 1% concentration, which can dilate the pupils and cause cycloplegia for several days at a time. Despite these side effects, atropine has been used in children for many years, mostly to help treat amblyopia (lazy eye) when patching does not work or is not feasible. More recently, it has also been studied in children for myopia control, and found to be safe and effective (up to 70% reduction in myopia progression). Further studies have found low-dose atropine (0.01%-0.05% concentration), to be safe and effective in reducing myopia progression and minimizing the side effects (pupil dilation & loss of focusing at near). Low-dose atropine is not commercially available, and needs to be made in a compounding pharmacy. It is not fully understood why atropine works for myopia control, but it works by a different mechanism than the peripheral defocus optical corrections discussed above
In summary, there are several methods to help slow down the progression of myopia. Treating myopia progression in children and teenage patients reduces the risk of developing sight-threatening eye diseases as they get older. This article has only discussed three of the most popular, effective, and simple methods of myopia control, but others do exist. If you or your child’s myopia continues to progress, it is important to discuss myopia control options with your optometrist. Myopia progression is a popular field of research, and hopefully new and even more effective treatment options will arrive in the future.
Primary Eye Care Centre 