There are several types of changes in the clarity of vision, the most famous are myopia and hyperopia. Astigmatism often goes "bundled" with these diseases, sometimes from birth. In an easy degree, it is in most people, and does not cause discomfort. In other cases, pathology significantly impairs vision and requires correction.
Astigmatism - what is it?
Translated from the Latin language, the problem in question is defined as the absence of a focal point. To create a correct image, the cornea of the eye and the lens must be shaped like a ball for soccer (soccer). Due to the ideal roundness, the light is correctly refracted and focused exactly in the center of the retina at one point (macula). Astigmatism is, in simple words, a curved cornea or lens (less often), like a ball for American football or rugby. Because of the elongation along one of the axes, the light is not refracted correctly, and several focusing points are formed.
The figure below helps to better understand astigmatism - what is it, and what is the mechanism of image formation on the retina. The picture shows a healthy eye, with a spherical cornea and a lens. The rays are refracted with the pupil identically from all directions, and converge at one point in the center of the retina. The second eye in the figure, struck by astigmatism, transmits light from different angles. Because of this, there are 2 or more focus points. They can be placed in front of the retina or behind it, and the person will see everything blurred or deformed.
Astigmatism - the causes of
The factors that cause this disease are classified into 2 main groups. The causes of astigmatism can be congenital and acquired. In the first case, it is impossible to influence the risk of developing a pathology, or to do its prevention. Acquired disease occurs already during a person's life under the influence of external adverse conditions.
Congenital astigmatism - causes
99% of the world's population have a described visual defect. Just the degree of curvature of the cornea or lens is so small that the astigmatism of both eyes does not exceed 0.4-0.5 diopters. This is a small indicator that does not affect visual acuity and does not cause inconvenience in everyday life. Discomfort occurs when the curvature is more than 0.75 diopters. The only reason provoking a serious congenital astigmatism of the eyes is heredity. Because of certain parental genes, the child develops a curved cornea or an elongated lens along one of the axes.
Acquired astigmatism - causes
Violation of the sphericity of certain parts of the eye can occur in adulthood. Acquired or secondary astigmatism - causes:
- trauma of the eye with damage to the lens or cornea;
- ophthalmological surgical interventions;
- keratoconus ;
- burns of the conjunctiva or cornea;
- keratitis ;
- corneal dystrophy ;
- inflammatory processes in the eye;
- severe eyelid disease;
- acute bacterial and viral infections of the eyes;
- seams, scars on the cornea.
Astigmatism - species, classification
In ophthalmology 5 forms of the considered pathology are distinguished. Curvature of the lens or cornea is always combined with either hyperopia (hypermetropia) or myopia (myopia). In accordance with the concomitant disease, astigmatism is classified:
- hypermetropic;
- myopic.
Given the definition of astigmatism, this is the elongation of the cornea or the lens along one of the axes (vertical or horizontal), ophthalmologists estimate its severity along the meridians. If we mentally divide the eye into 4 equal parts by 2 perpendicular lines, in each region there should be identical and absolutely symmetric parts of the pupil. If the cornea or the lens is curved along one of the meridians, the quarters will be extended along one of the axes, as shown in the figure. This characteristic determines the simplicity and complexity of the pathology.
Simple hypermetropic astigmatism
The described type of disease is a combination of normal refraction of light in one meridian, and incorrect - in the other. It is possible to define such astigmatism in another way, that this is the emergence of 2 points of focusing. One is located correctly, in the middle of the retina, and the other is behind it. Hypermetropic astigmatism of simple form causes tangible, but not severe visual impairment. It is well amenable to therapy or surgical correction.
Complex hypermetropic astigmatism
In the presented case, the light is refracted incorrectly in both meridians. Complex astigmatism of the hypermetropic type is farsightedness along the 2-axes, but to varying degrees. As a result of incorrect refraction of light by the lens or cornea, no center of focus is formed on the retina. They are located behind it at different points, one farther, the other closer.
Simple myopic astigmatism
This variant of the disease is easy to understand by analogy with previous types. Knowing the definition of myopia ( nearsightedness ), it is clear and combined with it astigmatism, that this is the formation of one of the points of focusing in front of the macula. On the retina because of this, not a clear image is formed, but a blurred spot. A simple astigmatism of this type implies the presence of a second focusing point exactly in the macula. This type of pathology leads to perceptible myopia, but it is well amenable to correction, especially by surgical methods.
Complex myopic astigmatism
The presented form of visual impairment is characterized by the curvature of the cornea or lens in the 2 meridians. For this reason, myopic astigmatism of complex shape is accompanied by severe short-sightedness. In the macula, there is not a single point of focus, they are all located in front of it. On the retina there is only a large and very diffuse light spot.
Mixed astigmatism
The considered variant of the disease is considered to be the most complex and leads to serious visual impairment. Astigmatism mixed - what is it: myopic refraction of light in one meridian and hypermetropic on another axis. As a result, there is not a single point of focus on the retina. If the above-described types of astigmatism, including complex ones, suggest the concentration of light rays behind or in front of the macula, then the mixed form unites these problems. One focus point is located behind the retina, and the other does not reach it.
Astigmatism - symptoms
The clinical picture of the pathology is non-specific, up to a certain point may not be associated with the disease. Possible signs:
- fast eye fatigue;
- defocus of vision;
- headaches predominantly of a pulsating nature;
- blur, distortion, doubling of the perceived image;
- the need to squint when looking at objects;
- palpable eye tension;
- pain, burning sensation in the eyes ;
- redness of proteins due to poured blood vessels;
- feeling of the presence of sand in the eyes.
The severity and number of these symptoms depends on the degree of astigmatism:
- Weak - up to 3 diopters. This is the most common and favorable variant of pathology, because it is well treatable by any existing methods.
- Average - up to 6 diopters. The signs of astigmatism are expressed so much that the corrections to the glasses no longer succumb. Lenses or surgery are needed.
- Heavy - more than 6 diopters. This form is characterized by gross changes in the shape of the cornea. The problem can only be rectified by operational methods.
Astigmatism - treatment
Therapy of curvature of the cornea or lens depends on the degree of the disease and the severity of its clinical picture. Correction of astigmatism is carried out in 4 ways, often they are combined with each other:
- wearing special contact lenses ;
- use of glasses;
- classical operation;
- laser surgery.
Lenses with astigmatism
This treatment option is suitable for correcting the mild and moderate severity of the pathology. There are 2 types of lenses:
- External. Points for astigmatism are selected individually for each patient after a thorough diagnosis, during which the stage of the disease and its exact form are determined, with an explanation of the angle of focus deflection. Lenses have a cylindrical shape and a complex structure. In some patients ophthalmologist wearing such glasses provokes unpleasant sensations - pulsating headaches, pain in the eyes, visual discomfort and dizziness.
- Contact. Early for the correction of astigmatism, extremely rigid lenses were used, which caused difficulties in their use. They traumatized the eye, accompanied by constant dryness, burning, sensation of sand and other inconveniences. In modern ophthalmology, toric contact lenses are often prescribed. They are soft, but have a special spherocylindrical shape. This provides a qualitative correction of vision without the disadvantages of rigid devices.
Neither glasses, nor contact lenses are effective options for getting rid of astigmatism. They simply help the person to see more clearly, but do not eliminate the main cause of the pathology. Lenses will have to be constantly changed, and vision will gradually deteriorate. The only effective way to treat this disease is radical treatment - surgical intervention.
Astigmatism - eye exercises
Visual gymnastics is prescribed to patients with the described disease, but only for the prevention of visual impairment or at the earliest stages. Even daily and prolonged exercise is not an effective method, how to cure astigmatism. Gymnastics does not help to restore the correct shape of the cornea or the lens, simply relieves tension from the eyes and improves local blood circulation.
The standard complex includes 4 basic exercises, after each of them it is necessary to cover the eyelids for 5-10 seconds and relax:
- Look up, then down. Repeat 10-15 times.
- Direct the view diagonally (maximally) up and down. Repeat for each side 5-8 times.
- Look left, then right. Repeat 10-20 times.
- Rotate the eyes in the direction and counterclockwise. Make 10-12 turns.
A good training of vision and the ability to quickly and correctly focus is a simple exercise that can be performed every morning. You should stand at the window and carefully consider any distant object - a tree, a neighboring balcony, a bird on a branch. After 20-30 seconds you need to sharply shift your eyes to a close object, for example, your own hand or pen on the window. Repeat 5 times.
Astigmatism is an operation
There are several options for surgical intervention in this disease. Astigmatism of the eye - treatment by radical methods:
- Keratotomy. During the operation, the radial (like spokes in the wheel) cuts with the scalpel are applied to the cornea. This helps to weaken the incorrect refraction of light in a curved meridian, which ensures the normalization of focusing in the center of the retina.
- Laser correction of astigmatism. This is the most effective and painless method, suitable for the treatment of pathology to 3-4 diopters. During the operation, the surgeon evaporates a portion of the curved cornea by the laser at a precisely calculated depth. As a result, it acquires the correct spherical shape, which reflects its ability to correctly transmit light.
- Implantation of toric phakic lenses. This method is assigned if the laser operation is impossible for any reason. The analogue contact toric lens, which is made of biocompatible materials, is implanted inside the eye (posterior or anterior chamber). This restores the correct focus and improves the clarity of vision.
- Lensectomy. This option is used in the treatment of severe cases of astigmatism. The operation is a refractive replacement of the lens. It is replaced by an artificial implant, which is a special intraocular lens.