Currently, soft contact lenses can be used for almost any type of abnormalities of vision refraction and, in the absence of contraindications, are a more convenient, comfortable alternative to glasses. Even such a complex violation as astigmatism, which was earlier amenable to correction only through glasses and hard contact lenses, which cause many inconveniences, can now be corrected with their help. To correct astigmatism, special toric soft contact lenses are shown, and this also applies to high-grade astigmatism. Let us consider in more detail what are toric lenses, what features these lenses have for selection and wearing.
What does "toric contact lenses" mean?
Toric lenses are lenses of a special design, which, unlike ordinary spherical lenses, is characterized by a larger thickness and spherocylindrical shape, i. E. they simultaneously have two optical forces. This is necessary in order to correct astigmatism with the help of a single value along the necessary meridian, and with the help of another value to correct the accompanying pathology of refraction - hyperopia or nearsightedness .
Astigmatism is an optical defect, in which the optical strength of the eye is not the same in different sections, i.e. In one eye, different types of refraction or different degrees of the same type of refraction are combined. Pathology in most cases is associated with an irregular (uneven, nonspherical) surface of the cornea or the lens, when passing through which the light rays are refracted in different ways. For the patient, this is expressed in the inability to focus the image, which appears blurred, fuzzy, and also such symptoms as headaches, eye pains .
In order for the action of the cylindrical component of the toric lens to be directed to the desired aspherical section of the cornea, such a lens must occupy a strictly defined position. Therefore, in addition to the characteristics listed above, the lenses for correcting astigmatism have a special fixing mechanism to keep them in a stable position, which is not affected by blinking of the eyelids, movements of the eyes and the head. Fixation can be achieved in various ways, among which is the thickening of the lenses in their lower part, truncation of the lower edge of the lenses,
Selection of toric lenses
Toric lenses can not be purchased simply by contacting the optics salon. For this, it is necessary to consult an ophthalmologist and undergo a survey including ophthalmometry, refractometry and some other methods. In addition, the age of the patient, the nature of his activities are taken into account. Initially, the selected test lenses are tested, for which the patient should carry them for about half an hour. If all the necessary parameters are met, then according to the selected characteristics, individual lenses are manufactured. Otherwise, the selection of lenses is continued.
When wearing toric lenses, it should be borne in mind that, since they have a greater thickness than usual, in no case can they be prolonged for a period of use, it threatens hypoxic complications (lack of oxygen supply to the tissues of the eye). It is necessary to observe the frequency of replacement, that
Also, one should not forget that toric lenses with a long period of wearing need daily care with traditional multipurpose solutions.
The leading manufacturers of toric contact lenses are such companies:
- Johnson & Johnson;
- Bausch & Lomb;
- Wohlk-Contact-Linsen et al.