Astigmatism is the distortion of the visual image, which is due to the different refractive power of some elements of the eye as an optical system. With this disease, a clear image of the seen object does not appear on the retina of the eye.
The fact is that the lens and cornea of normal healthy eyes has a direct spherical surface. Astigmatism is characterized by a violation of their sphericity, it is characterized by different curvatures in different directions: more convex in one direction and dense in the other, as, for example, an Uzbek torpedo melon.
As a result, the light rays that pass through the lens or the deformed cornea are focused not at one point on the retina, but simultaneously at several. Thus, the eye perceives the image is not clear. Basically, astigmatism is combined with either farsightedness (also called hyperopic astigmatism) or myopia (another name is myopic astigmatism).
Astigmatism is right and wrong. Improper astigmatism is most often acquired (clouding of the cornea, cicatricial changes). This form of the disease is characterized by the presence of different refractive power in certain parts of the cornea. Therefore, the visual image on the retina has a different degree of sharpness. Acquired astigmatism mainly develops after eye surgery and after injuries.
Correct astigmatism is characterized by deviations in the shape of the eye in the cornea. At the same time, the main meridians of the cornea (that is, mutually perpendicular axes that pass through the center of the pupil, one of which has the smallest and the other the greatest refractive power) have deviations from a strictly horizontal or strictly vertical position, while maintaining mutual perpendicularity. Depending on the combination of clinical refractions, complex, mixed and simple types of astigmatism are distinguished in the main meridians.
Astigmatism of a large degree always significantly reduces visual acuity. Small-scale astigmatism can be found quite often, and it does not have a significant effect on vision.
Astigmatism - Diagnosis
This disease is determined using objective and subjective research methods. When astigmatism is detected using the subjective method, during the study of visual acuity, an opaque shield with a narrow gap is placed in the test frame in front of the eye in question; when it is rotated, a position of the slit is selected at which the greatest visual acuity is manifested.
Thanks to corrective glasses, the refraction of this meridian is determined. Determine the refraction of the other main meridian and visual acuity by moving the shield with a slit 90 degrees. As a result, the difference in the main meridians determines the degree of astigmatism. Objective methods for determining astigmatism include ophthalmometry, skioscopy and refractometry.
Astigmatism - treatment
Today, there are three of the most common ways to correct this disease:
1. Laser correction of astigmatism. It is intended for adults (from 18 years old). The basis of laser correction is LASIK - an operation after which the patient's vision returns to normal, without any restriction.
2. Points. They are the most popular way to correct astigmatism, especially for children. In this case, glasses are used that have special cylindrical lenses.
3. Toric contact lenses. They are used to correct astigmatism of a low degree.
With astigmatism, muscle training is prescribed that is responsible for the accommodation of the eyes (video-computer vision correction, the use of drugs, laser stimulation). General strengthening measures, which include contrast shower, swimming and massage, are also recommended.
