Orthokeratology is a method that corrects vision during sleep, using a non-invasive technique. Orthokeratology lenses thus help correct mild to moderate myopia, or astigmatism. Wearing lenses at night compensates for an optical defect. And during the day, clear vision is achieved, without correction. This approach relies on changes in the curvature of the cornea. Orthokeratology has made remarkable progress over the past ten to fifteen years and could prove to be an attractive alternative to refractive surgery.

Orthokeratology took its first steps in the early 1960s. This technique involves wearing flexible lenses at night. This makes it possible to flatten the cornea, and causes a decrease, even a complete cancellation of myopia during the day.

Already, the ancient Chinese placed small bags of sand on their eyelids during the night, in order to reduce their myopia, and see better during the day. This is undoubtedly one of the first attempts at corneal reshaping. We owe the American Robert Morrison, doctor of optometry, the beginnings of orthokeratology: in fact, he was the first to have demonstrated that myopia could be stabilized by wearing special, flatter lenses. Then, during the 1960s, George Jessen put Morrison’s theory into practice by using rigid lenses to change the curvature of the cornea.

Orthokeratology is thus defined as the temporary reduction of myopia by wearing flat and rigid contact lenses capable of causing changes in the curvature of the cornea. For Dr. Gonzalo Carradeco, of the Complutense University of Madrid, orthokeratology is today recognized around the world as a safe and effective long-term procedure. The effects of this method were first seen as a side effect of polymethylmethacrylate (PPMA) contact lenses that flatten the radius of curvature over time.

Doctor Cary Herzberg, president of the IAOMC (International Academy of Orthokeratology and Myopia Control) thus affirms that “what was initially a method intended to reduce the refractive errors of myopic patients has become, following innovative design choices. , an advanced technique for modifying the surface of the cornea ”. Orthokeratology therefore concretely constitutes a non-surgical remodeling of the cornea. This technique was recognized by the American FDA (Food Drug Administration) and then imported in particular into France, but it is not, to date, reimbursed.

According to figures put forward by the national union of ophthalmologists in France, nearly 40% of French people have myopia. However, night lenses are intended particularly for adults suffering from mild myopia or astigmatism, and who have difficulty in supporting daytime or continuous lenses. Children and adolescents can also benefit from this orthokeratology technique, from 8 to 10 years old. Some studies even seem to show that this technique stabilizes the development of myopia in children.

For certain professions such as, in particular, high level athletes, the interest of not having to wear lenses or glasses during the day is real.

In practice, today, orthokeratology corrects myopia down to -4.00 D and astigmatism down to -2,5 D, both at the same time if necessary. All people with mild to moderate myopia, and who do not have eye diseases, are potentially affected. Orthokeratology is an alternative to refractive surgery.

These special rigid lenses are custom made. First, the wearer’s eyes are the subject of an in-depth study: a topography of the eye allows the observation of the reliefs of the cornea. It is advisable, for the fitting of the lenses, to use sodium hyaluronate.

Designed to be worn during sleep, these semi-rigid lenses have a specially shaped inner face. They induce a modification of the outermost layer of the cornea, the cells of the epithelium, during their natural migration from the periphery to the center.

In practice, these lenses exert a slight pressure: this reduces the curvature of the cornea during the night, causing a thinning of the central part of the cornea, while on the contrary the periphery thickens. The shape of the cornea being modified, myopia disappears artificially. This technique is reversible. Indeed, when the lens is no longer worn, the epithelial cells regain their regular distribution, and the central thinning is erased.

Concretely, reverse geometry lenses, of the tetracurve type, are used. It is essential to wear them for at least 6 to 8 hours each night in order to obtain a refractive effect. It should be known that refractive disorders imply, in fact, that the light rays no longer converge on the retina.

To obtain a satisfactory action, numerous tests are generally necessary. And as soon as the patient stops wearing at night, myopia reappears.

Significant progress has been made in orthokeratology over the past 10 to 15 years, and in particular in terms of technologies, the relationship between safety and efficacy, and even the control of myopia.

Wearing certain lenses permeable to oxygen therefore results in a transient flattening of the cornea, between 0,12 and 0,19 microns: the cornea is thus modified in its most superficial layers. This result is quite visible on corneotopographs.

The results of orthokeratology show an interest: a reduction or even a disappearance of myopia for about 24 to 48 hours. But this only concerns small myopias, less than or equal to 4 diopters, with a direct astigmatism not exceeding 1,5 diopters, or a maximum reverse astigmatism of 0,75 diopters

There is a risk of infection, which is why these orthokeratology lenses are not recommended before the age of eight. Strict hygiene must therefore be observed. Thus, nearly 120 cases of microbial keratitis were recorded between 1997 and 2007, which concerned Asian children aged 9 to 15 years. These infections were caused by improper use and improper care of the lenses. 

Dramatic corneal ulcers due to Pseudomonas have been reported by teams of Chinese scientists. However, tempers Dr. Herzberg in an article in the International Review of Ophthalmic Optics, “the figures collected in China are very telling – more than 1,5 million lenses have been inserted without any incidence of dangerous problems for the eyesight. ” In addition, this article also indicated that “associated with low doses of atropine, soft bifocal lenses and a modification of the lifestyle, orthokeratology is brought to play a considerable role in the slowing down of the progression of myopia and its dangerous complications for the sight ”.

Several optical treatment strategies are based on this theory of the influence of peripheral refraction on the course of myopia. Currently being tested, they are used to modify the curvature of the cornea in a myopic eye.