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Myopia is a serious problem that increasingly affects more and more children. In fact, in the modern world myopia is epidemic in nature. Today almost half of the young European population is myopic, and the percentage of high myopia (more than 6 diopters) already exceeds 10%.
Why is myopia so important? The most serious reason is its possible consequences, since high myopia can lead to low vision or even blindness. It is essential to know that myopia grows irreversibly during childhood and adolescence, approximately between 7 and 17 years. That is why it is important to intervene in this process precisely during this period. We explain how to stop the increase in myopia in childhood with contact lenses.
To slow or slow the progress of myopia in childhood, the most effective non-pharmacological method is orthokeratology, also called Ortho-K.
But what is it? Orthokeratology is based on the use of special lenses that the patient uses at night and removes them in the morning.. During sleep, the eye adapts to the curvature of the lens so that when it is removed in the morning, the myopia patient can enjoy 100% vision throughout the day without wearing glasses or contact lenses. The effect has a minimum duration of 18 - 20 hours, after which, depending on the case, the graduation slowly reverts to its initial situation. Afterwards, the special lenses will be worn again at night, regaining good vision. Additionally, orthokeratology can also treat astigmatism and hyperopia in childhood.
The main difference between Ortho-K and conventional contact lenses is that during the day it is not necessary to wear glasses or contact lenses, just like after refractive surgery, but without the risks associated with these interventions, since it is completely reversible and the eye returns to its normal state when you stop wearing the lenses.
When a child with myopia wears glasses, they create hydraulic forces that change the shape of the epithelium (an internal tissue). In this way, the epithelium becomes slightly thinner in the center of the cornea and thicker around the center.
The central part of the cornea flattens, reducing the diopters. The effect persists for at least 18-20 hours, after which it begins to slowly diminish. If the lenses are not used again, the cornea recovers its original structure and, with it, myopia returns.
Correction of hyperopia and astigmatism occurs by a similar mechanism. For this, other orthokeratology lens designs are used, which make the center of the cornea more convex (curved) or reduce its toricity (the geometry of the cornea in astigmatism).
Orthokeratology lenses in no case exert direct pressure on the cornea. The procedure by which this molding is achieved is due to the fact that the Orto-K lens exerts a pressure force on the tear that separates the lens-cornea. The tear layer redistributes the force so that the lens modifies the shape of the epithelium (outermost layer of the cornea), generating two zones: one for applanation and the other for suction. Are these changes at the superficial level those that change the structure of the epithelium and therefore changes in graduation.
Ortho-K can be used with children with myopia up to seven diopters, astigmatism up to five diopters and hyperopia up to four diopters (limits depending on the specific design of the Ortho-K lenses used). Ortho-K can also be used with more diopters, but in that case the eye will have a residual refractive error that must be compensated with glasses.
Research in recent years has shown that Ortho-K treatment of myopia is the most effective non-pharmacological method to slow the progression of myopia in children and adolescents. The earlier treatment is started, the better the results. In some cases, depending on the evolution of myopia, it is also possible to combine Orto-K with pharmacological treatments in eye drops, which is an effective drug to stop myopia (but does not correct the refractive error). Its use combined with Ortho-K opens the door to greater control of myopia.
Juan Gonzalo Carracedo
Doctor in Optometry and Vision, Associate Professor of the Faculty of Optics and Optometry of the Complutense University of Madrid and collaborator of AMIRES.
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