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Basic research has given us important clues to the environmental factors that incite axial elongation in children’s eyes—and new clinical technologies allow us to harness these insights and slow myopia progression in developing eyes.
Like autism and allergy, myopia is a well known condition that appears to have suddenly skyrocketed in prevalence. Comparing the myopia results of the 1971-1972 National Health and Nutrition Examination Survey to the same study three decades later (1999-2004) finds that the prevalence of myopia in Americans between 12 and 54 years of age increased from 25.0% to 41.6%.
This growth of myopia in the US is just part of a worldwide trend toward increasing myopia prevalence that cuts across cultures and gene pools, leaving little question that the increase is real, rather than an artifact of increased interest or poor experimental design.
Myopia is also called nearsightedness or shortsightedness. In simple terms, a person with myopia can not see clearly in the distance but they can see objects clearly that are nearby or a short distance away. Thus, the condition is also called near-sight (nearsightedness) or short-sight (shortsightedness).
While myopia may be a growing phenomenon, it can be readily corrected with glasses and contact lenses; and refractive surgery can provide a near-permanent correction. Why then is myopia control (as distinct from myopia correction) important?
First, there are enormous social and personal costs to myopia. The hundreds of millions of people around the world who wear glasses or contact lenses would be much happier if they could be less dependent on these devices—and they would collectively save billions of dollars in the process.
In addition, myopia, especially high myopia, is not benign: it is associated with increased risk of retinal detachments, myopic degeneration, myopic macular hole formation, and other serious morbidity.
Most important, myopia control is becoming possible. Once thought of as almost solely a product of genes, it is now clear that myopia development has a very large environmental component. With myopia rates rising rapidly around the world, we have to ask: What global change in the human environment is driving this?
The answer appears to concern education, economics, and electronics, which have forever changed the things we look at and how we look at them. Beginning in early childhood, the onslaught of near-vision demands from books, computers, video games, and handheld devices has an effect on how eyes develop.
Many efforts have been made to try to suppress and even reverse myopic development, including pharmaceutical, surgical, and corrective lens solutions. The most successful of these treatments was the use of antimuscarinic medications, such as atropine, pirenzepine gel, and cyclopentolate. However, this approach led to adverse side effects of light sensitivity and blurred vision. The drugs required were not readily available to the patient, making the treatment costly and impractical.
Orthokeratology, or the more current technique of corneal reshaping or refractive therapy (CRT), is a more effective strategy for addressing myopia. It is currently our best tool for myopia control and is a rapidly evolving modality.
Current overnight orthokeratology lenses produce a corneal shape that seems to be ideal for preventing axial length progression.1 The lenses alter how light is refracted by reshaping the cornea into a flatter surface while slowing axial length elongation in younger patients.
With today's corneal reshaping lenses, changes in vision can be dramatic. Patients often experience a 50% change in refraction the first night, and many achieve 20/20 (or a level of uncorrected acuity that they are happy with) within a week.
The ROMIO (Retardation Of Myopia In Orthokeratology) study found that the greatest change in axial length occurs in children aged 7 to 8 years old. Meaning that in order to gain the maximum effect from myopia control, treatment of children as young as 7 years old should begin.
Overnight wear of orthokeratology lenses appears to be less of a hassle for younger patients, perhaps because they do not have to bother with contact lenses during the day. Overnight orthokeratology also has a built-in signal for noncompliant patients – if they stop wearing the lenses, their vision becomes blurred – so they have incentive to follow practitioner instructions.1
Advancement in lens material not only has increased the rate at which orthokeratology can reach its maximum effect, but also it has increased safety. The material used in today’s overnight extended wear gas permeable lenses have high oxygen permeability and reduced risk of infection.
Factors such as inappropriate lens care, patient not following practitioner’s instructions, and continuation of lens wear despite discomfort have been shown to be the greatest risk factors to cause problems such as keratitis among orthokeratology lens wearers.
Training and certifications in fitting orthokeratology lenses, as required by the FDA, also has improved safety.
Orthokeratology is reversible, so if the patient is unhappy with the treatment, they can simply discontinue wearing the lenses.
Although RGP lenses are not known for being comfortable, orthokeratology lenses are worn only at night when the patient sleeps, so there is no discomfort from lens-lid interaction. These are large lenses (by RGP lens standards) that don’t move on the eye and provoke sensation. In addition, the materials used now are highly oxygen permeable.
Orthokeratology is satisfying for the practitioner. For many children, getting out of glasses gives a big boost to self-esteem; and their parents are gratified to be doing something positive for their children by reducing their myopic progression. Among kids who are active, orthokeratology is safer than glasses for contact sports and safer than ordinary contact lenses for swimmers. Myopia control is just one of many compelling reasons to add orthokeratology to a practice.