What are “night lenses,” also known as orthokeratology, and how do they work?

What are “night lenses,” also known as orthokeratology, and how do they work?

Myopia is the leading refractive error leading to visual impairment. In recent years, there has been an upward trend in this ophthalmopathology. The prevalence of disability due to myopia is 4.5 per 10,000 adults. Relatively recently, it has become possible not only to correct visual acuity but also to try to stabilize the progression of myopia using Ortho-K – through the use of rigid gas-permeable contact lenses of reverse geometry during sleep.

What are OK lenses made of?

The material for the manufacture of modern ortholenses is fluoro-silicone-acrylate. This is a complex composition that perfectly passes oxygen to the cornea, has increased strength, and does not cause allergic reactions. Specialists from the NASA space agency took part in the invention of the material called Paflufcon, testing various alloys in zero gravity. That is why the composition used in the production of ortholenses has unique properties.

The portholes consist of inner and outer hemispheres interconnected. The inner layer is designed to correct the corneal epithelium, and the outer layer is a regular lens. The latest generation lens has about five surface zones designed for better contact with the surface of the eyeball, which allows you to achieve a good result in a short time.

How do overnight orthokeratology lenses work?

With myopia, the cornea has an irregular structure, as a result of which a person cannot clearly see the image.

When using ortholenses overnight, the upper layer of the cornea changes its shape: in the center, it becomes flatter and thickened along the edges. The ophthalmic product, as it were, presses down on the epithelium, and its cells are redistributed in such a way that 100% vision returns to the patient for the whole day. He sees well without glasses or other optics.

With astigmatism and farsightedness, the correction occurs according to a similar principle, but the epithelial cells are redistributed in other directions. The epithelium then returns to its original irregular shape, so orthokeratology lenses are put back on at night to correct it. The impact on the cornea is carried out absolutely imperceptibly and painlessly, so the patient does not experience any discomfort.

Materials and methods

The mechanism for correcting myopia in orthokeratology is the redistribution of corneal epithelial cells under the action of an Orthokeratology lens. Hydraulic forces under the lens through the lacrimal layer act on the epithelial cells of the cornea. Those, in turn, gradually flatten in the center and increase in the middle periphery of the cornea. This creates a dosed flattening in the center and a slight increase in the curvature of the cornea around the optical zone. The normal anatomy of the cornea and the integrity of its layers are not violated. The changes are so small (10-30 microns) that they can be detected using a keratotopograph. However, these changes are enough to see well all day without glasses or contact lenses.

The use of OK lenses in children allows for achieving high visual acuity in mild and moderate myopia. With a high degree of myopia, it is possible to achieve good visual acuity with the possible occasional wearing of glasses in the evening. Choose the best qualified optician optometrist to have the best treatment.


After a short period of adaptation, children receive other benefits along with improved visual acuity. Our results confirm the conclusions of a number of colleagues: in the absence of contraindications, orthokeratology should be recommended for more active use in children with myopia.

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