which must be used at night in order to correct vision defects such as myopia, hyperopia, astigmatism and presbyopia.

Orthokeratology can represent a valid alternative to the surgical treatment of the aforementioned visual defects, however, it has some limitations and disadvantages that will be illustrated in the course of the article.

The regularity of the corneal surface is of fundamental importance for correct vision. Not surprisingly, this structure is one of the most important dioptric means of the eye and its surface acts as a converging lens capable of conveying - in association with the lens - the light rays towards the retina, favoring the perception of sharp images. .

Normal contract lenses are designed in such a way as to interfere as little as possible with the cornea; on the contrary, orthokeratological lenses are specifically made to modify - naturally, in a controlled manner - the corneal profile. This modification is made possible by the pressure exerted on the corneal surface by the deposit of tears that is created between the rigid lens and the cornea. In other words, the lens is designed in such a way as to leave a sort of imprint on the corneal surface, modeling it according to the specific needs of the patient (correction of myopia, astigmatism, hyperopia or presbyopia).

By modifying the profile of the cornea - which has a certain plasticity - it is possible to correct the refractive error that characterizes the patient's visual defect. Unfortunately, this remodeling is temporary.

, or rather, the mapping of the anterior corneal surface. This map shows in detail the shape and curvature of the cornea, providing essential information to be able to create personalized night lenses for orthokeratology, adaptable to the eyes and to the patient's needs.

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