What is Myopia?
Myopia is a common eye condition that is more frequently referred to as nearsightedness. When a patient is diagnosed with myopia this means that objects in the distance are blurry within their line of vision. Clear vision is characterized by the ability of the eye to accurately focus an image on the retina (Fredrick 2002). The focusing power of the cornea and lens, as well as the length of the eye are the main determinants of vision clarity. A myopic eye is longer than the non-myopic eye, and the longer the length of the eye the worse the person’s distant vision (Fredrick 2002).
Figure 4: This figure is comparing a non-myopic to a myopic eye showcasing the increase in length of the myopic eye.
A myopic eye focuses images in front of the retina due to its long length and/or the strength of the cornea and lens curvature. The shape of the myopic eye causes light rays to bend and refract incorrectly, inducing images to focus in front of the retina. Signals are sent to the brain for the eyes to grow bigger and make up for the lack of focus when this occurs in children. As shown in the difference between the myopic and non-myopic eye in Figure 4 above, the rapid growth results in higher risks of myopia and a harmful cycle resulting in consequential visual impairment. An emmetropic, or perfect vision producing eye, focuses an image perfectly on the retina. When images are focused behind the retina this condition is called hyperopia. Hyperopic patients are farsighted, allowing for objects that are in the distance to be clear but objects up close are blurry. The exact opposite of myopia is exhibited within hyperopia. Hyperopia is characterized by short length of eyes or too little curvature within the shape of the eye.
At birth most patients are hyperopic and gradually become less hyperopic until about 6 years of age when they achieve emmetropia (Fredrick 2002). Emmetropization is the process where the “refractive state of childrens’ eyes shifts in magnitude and reduces in variance to reach near emmetropia.” (Fredrick 2002). What is interesting to research is how much this shift towards emmetropia is genetically influenced and how much of it is actually modulated by early visual experience with outside environmental factors.
According to associate clinical professor of ophthalmology Douglas Fredrick, people with myopia are oftentimes classified into two groups (Fredrick 2002). These groups consist of low to moderate degrees of myopia labeled as “simple” or “school” myopia. These patients range from 0 to -6 diopters in their prescriptions. The other group of myopic patients are characterized as having “high” or “pathological” myopia with prescriptions greater than -6 diopters. Simple myopia is corrected with glasses or contact lenses whereas high myopia can be linked to potentially blinding conditions like retinal detachment, macular degeneration, and glaucoma (Fredrick 2002). Myopia management programs are essential to the prevention of pathological myopic conditions and the complications they are associated with later on in life.
What is the Crisis Around Myopia Management in Children?
Globally, the results of myopia are increasing significantly. It is “estimated that 1.4 billion people were myopic in 2000, and it is predicted that by 2050 the number will reach 4.8 billion” (Grzybowski et al, 2020). Statistics also show that in the early 1970’s only 25% of Americans were nearsighted (myopic). Today this percentage is increasing rapidly to around 40% of Americans having myopia with alarming rates of school-aged children being diagnosed. The rise of myopia in children is linked to increasing amounts of time spent reading, studying, and screen time usage. This trend introduces a linkage to not only the genetic components of myopia progression, but outside environmental factors too. Utilizing my background in sociology it is also important to reference that socioeconomically myopia can also have significant negative effects on peoples’ lives. Refractive visual errors from myopia can affect “ school performance, limit employability, and impair quality of life”(Grzybowski et al, 2020). Many ocular complications and diseases such as retinal detachment, glaucoma, cataracts, etc. are associated with myopia as well.
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Myopia management refers to the active use of various treatments in order to slow the progression of myopia. This is important particularly for children because the adolescent stage of life is when myopia is most likely to progress and worsen quickly. Myopia typically starts before the age of 10 and then gradually deteriorates every few months until stabilization in the early twenties. This is caused by the rapid growth of the eyes for both diameter and length in comparison to the normal rate of eye growth throughout adolescence. Eyes are supposed to grow steadily in childhood until stabilization during the end of the teenage years. The continuous rapid growth of eyes for adolescent myopic patients leads to continual visual deterioration and eye growth throughout the teenage years and into early adulthood. The ongoing deterioration through myopia progression is what leads to severely higher risks of eye diseases and visual impairment later on in life.
What are some effective methods of Myopia Management?
Throughout my capstone research project I focused on three different forms of myopia management: Orthokerontology lenses, MiSight lenses, and Atropine Drops
Orthokerontology Lenses (OrthoK)
Orthokeratology, or more commonly referred to as Ortho-K lenses, are specifically designed and fitted hard contact lenses that temporarily reshape the surface of the eye while a patient is sleeping. The vision improvements that are seen with Ortho-K lenses are reversible, but the consistency in wearing them helps maintain the improvements they induce.
The video above discuss how Ortho-K lenses help to decelerate myopic progression
In order to understand how Ortho-K lenses work, it is important to grasp the importance of the cornea in visual acuity. The cornea is a clear dome-like shaped window that is responsible for the eye’s ability to focus light onto the retina. Like shown below in Figure 6, by flattening the center of a patients’ cornea, which in return changes how light is bent and enters into the eye, Ortho-K lenses are able to gradually improve a patient’s vision with continuous overnight wear. These lenses are removed throughout the day but continue to keep the cornea flattened for a while improving vision without the need of glasses. However, failure to continuously wear Ortho-K lenses overnight causes eyes to revert back to their original shape and reintroduce refractive errors that are indicative of myopic vision.
Figure 6: This figure illustrates how Ortho-K lenses work to fit and adjust the cornea over night to decelerate the progression of myopia.
As shown through the clinical trials discussed by Dr Lipson in his journal article The Role of Orthokeratology in Myopia Management, myopic children using Ortho-K lenses were not progressing in myopia in the same drastic measures as other children using different corrective measures. Slower increase in axial elongation by 43% was observed when compared with myopic subjects who were wearing single-vision glasses to correct their myopia (Lipson 2022).
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Table 1: Listing of Published Studies on the Efficacy of OrthoK in Slowing Axial Elongation Compared with a Control Group. In this table results from Dr. Lipson’s studies on the use of ortho-k lenses in children of different locations around the world are shown in comparison to control groups of children wearing spectacles of soft contact lenses as forms of myopia management.
As shown in Table 1, Dr. Lipson found significant effects of Ortho-K lenses on children ranging from 37% to 63% axial reduction in comparison to spectacle and soft contact lens control groups (Lipson 2022). Ortho-K is unique in its ability to provide a solution for clear vision without the need of a corrective device like glasses or soft contact lenses throughout the day. The optical effect for the slowing of axial elongation is in effect for every second of a child’s waking hours. This improvement and maintenance of diminished myopic progression is imperative to early initiation for young children. The earlier the myopia management intervention, the greater the effect on limitation of axial length and severity of myopia late on in life.
One of the downfalls of Ortho-K lenses is the heightened risk of infection they pose for patients who have the inability to maintain good hand and contact lens hygiene. This is especially prevalent when discussing the role of Ortho-K lenses in children and adolescents because they often practice less ability to maintain adequate hand and contact lens hygiene. The biggest risk factor for eye infections is contact lense wear, so the introduction of daily hard lenses imperative for night visual correction may propose a significant increase in risks of infection for children. Risks of complications with Ortho-K can be diminished with compliance in recommended follow up care, accurate lens cleaning, precise fitting, and the use of highly permeable materials (Lipson 2022). Ortho-K lenses are not recommended for patients with severe dry eye or keratitis (Zhao et al, 2020).
MiSight Lenses
Studies have shown that hyperopic defocus can induce excessive eye growth leading to higher prevalence of myopia, and that myopic defocus can reverse eye growth. In accordance to myopic defocus to stunt or reverse axial elongation, manipulation of eye growth can occur when simultaneously introducing myopic defocus with an additional optic power. This simultaneous use of myopic defocus and additional optic power is referred to as “dual-focus optics” (Chamberlain at al, 2019). Adding simultaneous myopic defocus to hyperopic or plano correction lenses helps to diminish eye growth. This dual-focus optics is the basis for the Misight soft contact lens administered by CooperVision.
The Video above highlight's Phoebe's story with her experience using MiSight lenses, and how they have improved her quality of life.
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Figure 7: This figure is highlighting the dual focus approach the soft Misight lenses use towards reducing the progression of myopia by focusing the light onto the retina.
Misight lenses are the first and only FDA approved soft contact lenses that have been proven to slow the progression of myopia in children aged 8-12 (Chamberlain et al, 2019). They correct for nearsightedness while simultaneously diminishing the progression of myopia. A 3 year randomized clinical trial was performed and reported in the Optometry and Vision Science Journal of the American Academy of Optometry. Within this study myopic children with prescriptions ranging from -0.75 to -4.00 diopters and an astigmatism cylinder of less than -1.00 aged between 8 to 12 years were enrolled in a three year double masked randomized clinical trial comparing effects of Misight and regular refractive soft contact lenses.
Figure 8: This figure depicts the mean unadjusted changes in spherical refractive diopters for the Misight and control study groups in Chamberlain’s study. The mean adjusted differences can be seen to be approximately 0.4 diopters less at 12 months, 0.54 diopters less at 24 months, and 0.73 diopters less at 36 months for Misight lens wearers. This is indicative of a significant reduction in myopic progression of large diopter changes in refraction.
Figure9: This figure depicts the mean adjusted changes in axial length for Misight and control groups within Chamberlain’s study. The mean unadjusted differences are shown to be 0.15 mm less at 12 months, 0.24mm less at 24 months, and 0.32 mm less at 36 months for Misight lense wearers in comparison to the regular soft lens control group. This is indicative of a significant decrease in axial length progression and diminishing of myopic increase throughout the 3 year trial.
Figures 8 and 9 show that there is a strong correlation between decreased refractive diopter change and axial elongation with the introduction of Misight lenses. Misight lenses have proven to slow the progression of myopia by reducing the rate of axial growth and ultimately refractive diopter progression as well. Chamberlain’s clinical trial also reports overall satisfaction and ease of the younger aged subjects in regards to care and handling of insertion and removal of their MiSight contact lenses. These lensed are disposable daily soft lenses which are convenient and recommended for children who have never worn contact lenses before
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Figure 10: MiSight poster
I have personal experience with helping train and administer Misight lenses due to my experience working alongside Dr. Sheri Levack at Indiana Eye Doctors. Dr. Sheri Levack is a licensed optometrist certified to administer Misight lenses for children between the ages of 6-12. One of my responsibilities as an optometric technician at Indiana Eye Doctors is to train patients on insertion and removal of contact lenses. I helped train Dr. Levack’s first Misight lense patient who was a young girl of 9 years of age. Having personal experience seeing the initial difficulty of having a young child insert and remove the soft contact lenses gave me apprehension on the administration of Misight lenses initially. However, as she continued to come back for follow up appointments her independence and ease of insertion and removal of her contacts had grown tremendously. Before her initiation into the Misight program, Dr. Levack had shown me records of her previous progression with myopia. Annual exams were showing drastic changes of up to almost half a diopter (-0.50) every visit. This is an alarming rate of refractive error progression and created an increasing need to find a solution to slow this myopic progression. It has been about two years now since I helped her begin her journey with Misight lenses and she is now maintaining a better refractive error progression for her annual exams. There has been an increase in only -0.25 diopters in two years rather than -0.50 every individual year. The slowing of this progression of myopia and axial elongation will allow this patient to reach her early adulthood with a much lower myopic prescription, ultimately reducing her risk towards many ocular complications and increasing her quality of life.
Atropine Drops
Atropine is an anticholinergic blocking agent that plays a role in different ocular tissues in regards to slowing axial elongation and myopia progression. Atropine is actually the same chemical eye drops used for dilation during comprehensive eye exams. As shown in Figure 11 below, atropine helps to weaken contractions of ocular muscles that operate the iris and the lens. The iris, or the colored part of the eye, is essential in controlling how much light the pupil lets in. The lens is then the clear inner part of the eye behind the iris that works with the cornea to focus light onto the retina. Lower dosages of ophthalmic atropine in comparison to dosages used for dilation are introduced in order to slow down myopia progression. In simple terms, low doses of atropine help to relax the focusing mechanism within eyes. As discussed in terms of the dual-focus optics observed in misight lenses, the introduction of myopic defocus can actually reverse eye growth, stunting axial elongation, and ultimately diminish progression of myopia.
A research article titled Efficacy and Safety of Atropine to Control Myopia Progression: a Systematic Review and Meta-analysis in the BMC Ophthalmology journal discusses a clinical trial conducted on various dosages of atropine drop administration and their effects on myopia progression. Within these clinical trials myopia progression was shown to have been mitigated greater in treatment groups administered the atropine drops in comparison to control groups not administered. Three different dosages were used in studies to determine which dosage of atropine drop solution was the most effective and safe for myopic patients. A dosage of 0.05% atropine was determined to be the most optimal dose for myopia progression treatment (Zhao et al, 2020).
Figure 11: A poster from Dr. Bishop & Associates Optometrists that highlights how atropine drops work in dilation of the pupil to counteract excess focusing attributing to myopia progression.
Comparison and Contrast Between Each Method
Each individual method discussed for treatment of myopia progression has its pros and cons. Ortho-K lenses have been frowned upon by some practitioners because of the increased risk of infection they impose for sleeping in contacts. They also require a strict adherence to nightly wear or else they may continuously lose the progress they make on reshaping the cornea. Ortho-K lenses also significantly change prescriptions making it difficult to use glasses in emergency situations since the patients’ prescription may be constantly changing without strict adherence to their nightly lense wear. However, the nightly wear of Ortho-K lenses does allow for more flexibility in ensuring parental supervision of children administering the contact lenses themselves at night. Whereas Misight lenses worn throughout the day may not always ensure the capabilities of parental supervision due to the nature of how busy daytime can be for patients and their families. Atropine drops are the least expensive of the three methods and one of the most effective but there has not been much research into the individual dosages and science behind their diminishing of myopia progression.
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All three methods of myopia management are similar in their functionalities of slowing axial elongation and reducing refractive error diopter increase. Administration of Ortho-K lenses has also proven to have effective results when paired along with 0.01% atropine drop dosage .Kinoshita reported in the article centered around efficacy and safety of atropine to control myopia progression that the combination of the two reported significantly slower axial elongation in comparison to the use of ortho-K lenses alone. The optometrists at Indiana Eye Doctors administer MiSight lenses and use atropine drops most frequently in controlling myopia progression for their patients. My time spent working alongside them observing and discussing their decision regarding effective methods for myopia management will prove to be extremely valuable in my continued career path as a pediatric optometrist.