CURRENT CONCEPTS AND RESEARCH
IN MYOPIA CONTROL IN CHILDREN
Humans have been myopic for centuries, yet it is only recently that the famous clinics of Brien Holden, PhD in Australia uncovered the mechanism behind progression of myopia in children. Prior to that, it was thought that reducing or “under-correcting” children’s eyeglass prescription may be of benefit.
Another theory which proved not to be valid was to have children function without glasses in an attempt to control children’s increasing prescription strength. After years of research, it turns out that the critical part of myopia control is not so much related to the central part of vision, but instead what is happening in the “bullseye” area outside of the center that is instrumental in myopia control.
Two Treatment Zones:
Creates myopic defocus with image focus in front of the retina rather than behind it to slow axial elongation.
Ensure consistent myopic defocus across all prescriptions, changes in pupil size, and variations in lens centration.
Two Correction Zones:
Correct myopia in all gaze positions.
As illustrated, this bullseye pattern, in this case is a contact lens, creates two focal planes:
1) The central focal point, and
2) the myopic defocus point. This general principle is the method that is used in myopia control in all contact lenses and in eyeglasses used to control myopia progression.
In addition to this, low-dose atropine, which needs to be compounded, is used to aid in myopia control. Atropine acts on the ciliary muscle of the eye, and by relaxing this muscle, the progression of myopia is slowed.
YOUR CHILD IS MYOPIC, NOW WHAT?
Your child is myopic (nearsighted, shortsighted), and cannot see objects clearly when looking in the distance (eg. The board at school, across the street, etc). Prescribing eyeglasses do not alter the course of progression of myopia, however, there are therapies available to accomplish this.
If your child’s prescription is -1.00 D, and they are approximately 10 to 12 years old, then you can expect their eyeglass prescription to increase by about 0.3 to 0.5 per year until the ago of 20. There are eye-health benefits in limiting these changes year-over-year In addition to vision benefits, slowing down their myopia reduces their risks of glaucoma, retinal detachment and other eye diseases.
Atropine is currently being used in three concentrations: 0.01% 0.025% 0.05% ophthalmic solution in order to attempt to stop or slow the progression of nearsightedness in children. This is an “off-label” use for this medication. Studies have shown that this medication is effective in slowing the rate of progression of nearsightedness in children.
Once a drug has been approved by the FDA for one purpose the manufacturer produces a “label” to explain its use. A physician can then prescribe that drug for any purpose. The practice of prescribing a drug for a purpose other than that for which it is approved is known as “off-label” use. Off-label use is legal and does not necessarily mean that the drug is being used inappropriately. There are several companies currently finishing studies to obtain FDA approval for a commercially-available atropine preparation.
Atropine ophthalmic solution is normally used to cause the muscles in the eye to become relaxed. This widens the pupil and relaxes the muscles in the eyes that help you focus on up-close objects. Atropine ophthalmic solution is also used to dilate (widen) your pupil when you have an inflammatory condition or in post-surgery situations in which this effect may be helpful. Atropine is also commonly used in the treatment of “lazy eye” (amblyopia). Typically, Atropine is used in concentrations of .5 to 1% however, the concentrations used for myopia control are .01-.05% which results in minimal side effects.
SIDE EFFECTS FROM THE DRUG
Eye related side effects include: blurred near vision, sensitivity to sunlight, pupil dilation (the amount varies from patient to patient and concentration of medication used), stinging and burning, or swelling of the eyelids. However, these side effects are rare at low concentrations. .
General side effects of Atropine include: allergic reaction (difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives), an irregular or fast heart rate, hallucinations or unusual behavior (especially in children). Other, less serious side effects may be more likely to occur.
SEEING CLEARER IN THE DISTANCE
Although atropine is used to slow the progression of myopia, it does not clear up the distance vision that a child requires to be able to see the board at school, for example. This can be achieved with the use of special eyeglass lenses or by using contact lenses. Both of these methods address the periphery of the retina focus, as well as the center.
There are two basic types of contact lenses used for management and control of myopia in children. They are used in different ways, but both rely on bringing the periphery of the retina into focus.
Custom Rigid Gas-permeable Contact Lenses.
Orthokeratology: These lenses are custom made and are used by the child when asleep. Think of these like a bite-retainer in dentistry that helps to maintain a child’s t in proper alignment while sleeping. That is exactly what this type of contact lens does, it “re-aligns” the shape of the cornea.
The contact lens works by altering the pattern of curvature of the cornea and creating a circular pattern in the near-periphery of the cornea. This circular pattern was theorized and developed by professor, Dr. Brien Holden of Australia. When fit properly, the lens looks like this:
This is an ideal fit because the center of the cornea:
Is being touched by the lens, and an outside ring
Coloured indicator shows the bullseye focus meant to create a different focal plane.
With this fit of lens, a child will wake up in the morning, remove the lenses and see clearly for the rest of the day. He or she will also get the added benefit of controlling changes in their myopia and the axial length of the eye.
Since we are dealing with a lens which is worn overnight, in a closed-eye situation, care needs to be taken that they eye surface is compatible with the contact lens, and that there are no signs of “wear and tear” on the eye. Ideally, the specialist should be able to look at the eye surface and not witness any detectable signs of lens wear. In the hands of a qualified practitioner, this type of contact lens wear is safe, and most certainly the benefits outweigh the small risk.
Risks include inflammation, redness and infection, however these minor problems can normally be managed quite simply by a qualified practitioner.
HERE ARE SOME REFERENCES WITH SUMMARIES REGARDING ORTHOKERATOLOGY AND MYOPIA CONTROL
This 2019 report by the American Academy of Ophthalmology analyzes 13 articles on the effectiveness of orthokeratology in slowing down myopia progression and concludes: “Orthokeratology may be effective in slowing myopic progression for children and adolescents, with a potentially greater effect when initiated at an early age (6–8 years). Safety remains a concern because of the risk of potentially blinding microbial keratitis from contact lens wear.”
Another article published by the National Center of Biotechnology Information states: “Orthokeratology lenses, worn overnight to reshape the cornea, are one of many recent modalities used to slow down the progression of myopia in children. This treatment has been proven successful, as evidenced by decreased spherical refractive error and axial length relative to the control at interval follow-up ranging from 6 months to 5 years.”
“The assessment demonstrated that ortho-K generally reduced the axial elongation by approximately 50% over a 2-year period. The impact was greater in individuals younger than 9 years. The rate of myopic progression was most affected in the first and second year of treatment, but some effects were still noted in the third year. None of the studies measured adverse events as a primary outcome.”
This comprehensive article on ‘Myopia and orthokeratology for myopia control’ was published in 2018 by Professors of the Polytechnic University Hong Kong.“In summary, several cohort studies have shown that orthokeratology is effective in retardation of myopia progression in children with a two‐year reduction rate ranging from 30 percent to 59 percent and a five‐year reduction rate of 30 percent.”
An article published in December 2017 by the Tzu Chin University in Taiwan covers the findings of a 12-year cohort study and concludes:“Overnight orthokeratology was effective in slowing myopia progression over a twelve-year follow-up period and demonstrated a clinically acceptable safety profile. Initial higher astigmatism power was found to be associated with increased change of refractive error during follow-up years.”