1 Definition of astigmatism
What is astigmatism? This is a state in which a refractive error is observed when a ray of light entering the eyes is focused at two different points: before and behind the retina. Patients with astigmatism report poor vision from a distance and close-up. They may also have headaches.
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The disease leads to poor visibility of all objects, regardless of whether they are nearby or far away. Usually occurs when the cornea has the shape of an elongated ellipsoid, rather than a ball. Uneven shape leads to the fact that the rays of light entering the eye are focused in many places, and not just on the retina.
With the astigmatism of the eye that looks at the point, it sees not a point image, but two linear ones, called focal ones.
With the correct construction of the eyes, the rays of light are focused at one point: on the retina. With astigmatism due to irregularities in the curvature of the cornea, the beam of rays passing into the eye is focused at 2 points, causing the appearance of blur effects. The irregular shape of the cornea( reminiscent of a rugby ball fragment) is responsible for 98% of cases of eye defects( so-called corneal astigmatism).In rare cases, this visual defect can also be a consequence of an irregular lens shape( so-called lens astigmatism).As a rule, it appears as a result of a birth defect in the lens. Sometimes congenital astigmatism develops as a result of cataracts.
The disease is very common, the disease affects 1/3 of the population, usually from birth. In many cases, people with myopia or hyperopia have a small astigmatism. A small degree of this refractive defect is considered normal and does not require correction.
In mixed astigmatism, the symptoms of myopia and hyperopia occur simultaneously. This combination makes it impossible to see clearly.
2 Causes of
As a rule, astigmatism depends on the shape of the eyes. Both the lens and the cornea can be partially responsible for the astigmatism of one eye.
The main reasons that can lead to astigmatism:
- Keratoconus. The appearance of astigmatism in adults can be the first sign. It is a progressive disease in which the cornea takes on a conical shape. The cone appears during puberty, usually in both eyes, but not simultaneously. Patients report a worsening of vision for a short time and the consequent need for frequent glasses change. In addition, they have a reduced tolerance of contact lenses. In the case of an advanced stage of the disease, a corneal transplant may be required.
- Pterygium is a change that consists in the proliferation of the conjunctiva on the cornea. Most often occurs in people who spend a lot of time in the sun. Treatment of the disease is performed surgically.
- A wound on the cornea can leave a scar that causes astigmatism.
- Stitches after trauma or surgery cause a risk of eye strain, which can lead to corneal pathologies.
The most common symptom is eye fatigue. Often observed in mild form with disease. A more serious lack of vision is the restriction of its severity. Sometimes the visible images are deformed.
The disease is manifested by difficulties in focusing the objects seen( foggy vision from afar and from a close distance), frontal headaches. With a small astigmatism, the only symptom can be frequent blinking, since people with this lack of vision try to get a clear image with the help of a sharp change in the focal length. A person suffering from astigmatism sees the stars as spots, straight lines in the form of curves. Does not see at the same time equally sharp vertical and horizontal lines( for example, only one shoulder of the cross sees clearly).With diffuse outlines, a sense of space disturbance may occur. In young children under 3 years of age, a large astigmatism can lead to amblyopia of one or both eyes.
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4 Diagnosis with ophthalmologist
To see if you have astigmatism, you will need to visit an ophthalmologist. When such a vision problem was identified, the first tool for its detection was the keratoscope - the invention of the Portuguese ophthalmologist A. Placido. This is a disk with white and black consecutive circles. The study includes observing the shape of their reflection on the cornea. The degree and axis of the astigmatism of the eye is measured by an ophthalmometer( keratometer).
The most accurate method for determining astigmatism is computer topography.
It uses a Placido disk image reflected on the surface of the cornea, which is recorded with a camera, and then transferred to a computer and analyzed. The result of the study is a colorful map and a section of the surface of the cornea, a map of the digital value of its curvature. The last study is necessary before the procedure of laser correction of eye defects. In everyday practice, an autorefractometer equipped with a surveyor is used. All these studies are painless, conducted with eye examinations by an ophthalmologist using instruments.
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5 Forecast of daily life
Disease interferes with daily life, in actions that require a good vision both from a distance and close. Difficulties depend on the degree of vision defect and how it can be effectively corrected. Absence or ineffective correction can lead to illnesses, such as chronic inflammation of the conjunctiva, eyelid margins or permanent headaches, increased fatigue when working on a computer. Children sometimes have an unwillingness to learn, and adults have a blurred vision and increased fatigue when driving, which makes them unable to see the lights of other cars. Therefore, contact lenses and corrective glasses with this lack of eye should be accurately matched.
Vision can be corrected with spectacles with cylindrical glasses or soft toric lenses, but if the surface of the cornea is destroyed to a large extent( for example, due to scarring, diseases) or astigmatism is large, then an optical disc.
If the visual defect is corneal, you can treat the astigmatism of the eyes with laser correction. If the origin of the defect is associated with the lens, for example, it arose as a result of cataracts, the problem disappears after the operation to remove the underlying disease. In the case of cataracts, the operation consists in replacing the clouded natural lens with an artificial lens.
With a small astigmatism( up to 1 diopter), glasses are mostly worn only for study, driving, working on the computer. And almost every person has a so-called physiological astigmatism: about 0.5 diopters, because the correct cornea is destroyed more vertically than horizontally.
6 Cylindrical lenses
Treatment of a disease depends on several factors, such as: the age of the patient, his lifestyle and profession at the present time. Most often, the treatment is associated, however, with the use of contact lenses or glasses.
Visual defects and coordination impairment are corrected by cylindrical lenses. In some forms of the disease, that is, in complex astigmatism or mixed, combine a spherical( eliminating myopia or farsightedness) with a cylindrical correction( getting rid of astigmatism) with the help of toric lenses. If the patient does not tolerate the proposed cylindrical correction, it may occur when using glasses:
- image distortion in the form of a wall bend or unevenness of the floor.
In this case, the cylindrical correction should be reduced. Sometimes these patients can get a good visual acuity with the help of spherical lenses instead of cylindrical lenses.
7 Astigmatism progression
Over time, astigmatism passes through different phases, and then becomes relatively stable. If in addition there are visual defects or eye diseases that deform the cornea, astigmatism may deteriorate.
There are many types of astigmatism. Not all astigmatists should wear corrective glasses. Some visual defects do not require a comprehensive correction.
The situation becomes more complicated if there is an additional short-sightedness or farsightedness. Children with this disorder should wear glasses from the second year of life. You can wait until the fourth year of life, but then the eyes of the child should be under the supervision of an ophthalmologist who will monitor the correct development of vision.
Other possible means of vision correction for people suffering from astigmatism are contact lenses and surgical operations.
8 Usage for laser treatment
Glasses and contact lenses certainly correct some of the visual deficiencies, however they, like bandages, are temporary solutions that do not heal the root of the problem, as is the case with surgical intervention.
The LASIK procedure is the most common and acceptable form of laser vision correction since it successfully passed clinical trials in the US in 1991.It can completely eliminate or reduce the need to wear glasses or contact lenses by modeling the shape of the cornea.
Surgical treatment of astigmatism involves the use of laser operations: Lasik( up to 6 diopters), PRK / Lasik( up to 2.5 diopters) and Epi-Lasik( up to 3 diopters).The choice of the correction method is carried out, in particular, depending on the thickness of the cornea. The most effective method of Epi-Lasik is recommended in the case of a thin cornea. The goal of these therapies is to give the cornea of the eye the right shape.
The procedure for laser vision correction takes only a few minutes and is performed under local anesthesia( eye drops).Laser vision correction reduces the need for wearing glasses or contact lenses and gives the eye a natural shape, closer to the ideal. Immediately after the procedure, you can go home, you can go to full activity in a few days.
To cure eyes of astigmatism, it is sometimes necessary to perform procedures using intraocular lenses( IOLs).They are used in procedures for the removal of cataracts and are called toric lenses. The company Alcon produces one of the most modern toric lenses, providing a more accurate correction of vision.