Eye diseases. Astigmatism (most important)

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Eye diseases. Astigmatism (most important)

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44. Astigmatism

Astigmatism is a refractive error in which different types of ametropia or different degrees of one type of ametropia are combined in one eye.

Etiopathogenesis of astigmatism and its forms. The development of astigmatism is based on the unequal refraction of light rays in different meridians of the eye, which is associated with differences in the radius of curvature of the cornea (less often the lens). On the two main mutually perpendicular meridians, the strongest and weakest refractive power is observed. As a result of this feature, the image on the retina always turns out to be fuzzy, distorted. As a rule, the cause is an anomaly in the structure of the eye. However, such changes can occur after operations, eye injuries, diseases of the cornea.

There is a simple astigmatism, in which emmetropia is noted in one of the main meridians, and ametropia (myopia or hypermetropia) in the other; complex astigmatism, when ametropia of the same type, but of varying degrees, is noted in both main meridians of the eye; mixed astigmatism, in which myopia is noted in one of the main meridians, and hypermetropia in the other.

In astigmatic eyes, there are main meridians with the strongest and weakest refractive power. If the refractive power is the same throughout the meridian, then astigmatism is called correct, if different, incorrect.

With direct astigmatism, the vertical main meridian has the strongest refraction, with the reverse horizontal. When the main meridians pass in an oblique direction, one speaks of astigmatism with oblique axes. Correct direct astigmatism with a difference in refractive power in the main meridians of 0,5 diopters. considered physiological, not causing subjective complaints.

Clinical picture and diagnosis of astigmatism. Patients complain of a decrease in visual acuity, rapid eye fatigue during work, headache, and sometimes vision of objects twisted. Spherical convex and concave glasses do not improve vision. The study of refraction reveals the difference in the refractive power of the eye in different meridians. The basis of the diagnosis is to determine the refraction in the main refractive meridians.

Treatment of astigmatism. Spectacles with cylindrical or spherical-cylindrical lenses (astigmatic lenses) are prescribed. The constant wearing of such glasses maintains high visual acuity and good performance. That is why patients with such a pathology for a long time can do without surgery.

Author: Shilnikov L.V.

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