In astigmatism, astigmatism or astigmatism, the healthy curvature of the cornea is impaired due to various possible causes. Recognition of dots is affected as a result; they are perceived as strokes.
What is corneal astigmatism?
Astigmatism is also known as corneal curvature or astigmatism and is an eye defect that can affect sharp vision. Astigmatism is when the curvature of the cornea is different from the natural curvature that the cornea of a person with normal vision has. Due to a corneal curvature, light falling on the eye cannot be centered on the retina, which results in dots being perceived as blurred lines, for example. For this reason, astigmatism is often referred to as astigmatism: Instead of dots, blurred rods are seen. Also, the term astigmatism is derived from the Greek syllable ‘a’ (which means ‘not’ in German) and the Greek word ‘stigma’ for ‘dot’; thus, the word meaning of astigmatism is that of ‘dotlessness’.
Causes
In most cases, astigmatism is congenital. However, it can also be the result of a severe injury to the cornea. Depending on the cause of astigmatism, it is referred to as either regular or irregular astigmatism. Regular astigmatism is usually hereditary and is caused by perpendicular planes having different refractive power. In most cases of regular astigmatism, the refraction of the vertical plane is higher than the refraction of the horizontal plane; in rare cases of corneal curvature, the horizontal plane has a higher refraction. Irregular astigmatism is characterized by unequal refractive powers or curvatures of the cornea, which may be due to scarring injuries, for example. Another possible cause of irregular astigmatism is cataracts, which can lead to opacities of the optical lens.
Symptoms, complaints, and signs
Symptoms of astigmatism depend on the severity of the curvature and the resulting refractive errors. Many people have mild astigmatism and hardly notice it in everyday life, if at all. Symptoms only appear when the curvature is more severe and does not allow a sharp image both near and far. The eye now tries to make the image sharper by accommodation (adjustment of the refractive power) and overstrains the eye muscles in the process. Those affected notice this in burning eyes and headaches. In addition, the eyes tire more quickly due to the strained vision. Astigmatism not only causes problems with blurred vision, but the image is also distorted because only focal lines appear on the retina and no focal point. This is why this form of ametropia is also called astigmatism. Circles, for example, are then perceived more like ovals. Due to the uneven refraction of light, the affected eye may also react more sensitively to light. Astigmatism is usually congenital and does not normally worsen unless nearsightedness, farsightedness or presbyopia is added. Then vision may also deteriorate further. Children with congenital severe corneal curvature may develop amblyopia.
Course
The course of astigmatism depends, among other things, on its cause; if regular astigmatism is present, which is often congenital, the astigmatism usually does not change further. However, astigmatism that is not treated (for example, by optical aids such as contact lenses or glasses) can lead to severe headaches after some time; the headaches are caused by the fact that in case of astigmatism the eye is constantly trying to achieve a sharp image by accommodation (adjustment). The course of irregular astigmatism, which is based on a progressive disease such as cataract, usually depends on the course of this very disease. Thus, irregular astigmatism can worsen over a lifetime (or improve with appropriate therapy for the underlying disease).
Complications
Astigmatism can be regular or irregular. Accordingly, the type and nature of the associated complications differentiate.Usually both eyes are affected, often with different visual acuities. Far-reaching problems arise if the astigmatism is not treated in time. Congenital astigmatism can be detected by an ophthalmologist before the age of two. If this is not done or if it is detected incorrectly, the visual defect can worsen significantly. Furthermore, important nerve pathways in the brain can develop only with deficits and, in the worst case, not at all. Affected patients suffer increasingly from headaches and eye pain. Vision deteriorates with age to the point of barely being able to perceive objects. The child should be fitted with special plastic glasses at an early stage. Depending on the degree of astigmatism, the healthy eye is temporarily masked. Sometimes an accident, serious illness or trauma can also scar the cornea of the eye. If astigmatism does not occur until adulthood, it can be corrected relatively easily by laser surgery. However, this may only be performed after the age of 18. Complications such as under- or over-correction of the astigmatism, infection or damage to the optic nerve can also occur during the procedure. Not every laser surgery guarantees that the patient will not need glasses afterwards.
When should you go to the doctor?
An ophthalmologist should be consulted if there is regular eye irritation or decreased vision, whether near or far. By interviewing the patient and examining the eyes, the medical professional can determine whether astigmatism is present and suggest appropriate treatment following the diagnosis. If the condition is diagnosed at an early stage, the symptoms can be counteracted with the help of a visual aid. However, if the astigmatism remains untreated, it can progress to a severe stage. A medical examination is therefore recommended at the latest when serious visual disturbances occur and are accompanied by headaches, burning eyes and eye pain. If astigmatism has already been diagnosed, the responsible ophthalmologist should check the diopter and adjust it if necessary. So parents who feel that their child has poor vision should always make an appointment with an ophthalmologist. With infants who do not make proper eye contact or show other signs of decreased vision, a pediatric ophthalmology specialty clinic should be consulted. Other contacts include orthoptists and ophthalmology specialists.
Treatment and therapy
Similar to the course of astigmatism, the choice of an appropriate treatment for astigmatism depends on its form; if regular astigmatism is present, which is mainly congenital, astigmatism can be counteracted, for example, by glasses or hard contact lenses. Eyeglasses used to counteract astigmatism are equipped with so-called cylindrical lenses. If irregular astigmatism is present (as a result of corneal injury or eye disease), it cannot be counteracted by glasses. If the cornea is free of scars after an injury, hard contact lenses can be used for correction. If, on the other hand, the cornea shows scars after a corneal curvature, a possible treatment is corneal transplantation. In addition, astigmatism can be treated with surgical methods or laser treatments; the degree to which visual acuity approaches normal vision after surgery depends, among other things, on the degree of astigmatism: as a rule, the chances of achieving normal vision are higher with less pronounced astigmatism. In this context, surgical interventions entail various specific risks.
Outlook and prognosis
Congenital astigmatism cannot be cured, but it can be corrected with appropriate lenses or contact lenses. The overall prognosis is favorable if the visual defect is corrected by appropriate spectacle lenses or contact lenses, because the curvature of the cornea usually remains the same and does not deteriorate further. If a family tendency is known, it is recommended to have the child’s eyes examined already. The earlier the curvature is detected, the greater the chance that the eyes will not be unnecessarily overstrained, which would lead to a deterioration of vision in the long term. The situation is different in the case of acquired astigmatism, which can be caused by injuries to the cornea or cataracts.In this case, the eyes should be checked regularly, because blurred vision can cause headaches and further deterioration of vision. Eye surgery can also temporarily cause corneal curvature, for example during cataract or glaucoma surgery. In these cases, however, the curvature recedes after some time and vision is not permanently impaired. Surgical procedures or laser treatment can improve vision, but they cannot completely cure astigmatism. In addition, any surgery carries some risk of complications.
Prevention
Prevention of hereditary regular astigmatism is usually not possible. If children are already diagnosed with corneal astigmatism, it may be helpful to start treatment early to prevent refractive errors that occur later. An injury-related astigmatism can be prevented by protecting the eyes sufficiently in assessable dangerous situations. An aggravation of a disease-related astigmatism can be counteracted by early start of treatment.
Aftercare
In regular astigmatism, there is an inherited corneal curvature. This persists throughout the patient’s life. Follow-up care thus becomes a permanent issue. Patients consult their ophthalmologist at certain intervals. He or she can measure the radius of curvature using an ophthalometer or videokeratoscope. After a control check, he prescribes a new prescription for glasses or contact lenses. If the prescribed aids are not used, headaches may develop regularly. Concentration may also be weakened. Blurred vision becomes too strenuous for the eyes, which is the most significant complication. The situation is different with irregular astigmatism. Here, the corneal curvature takes a progressive course and a cone-shaped bulge develops. The aftercare consists in the use of contact lenses. The treating ophthalmologist prescribes these. Routine eye examinations take place at certain intervals. Glasses, on the other hand, are not suitable for correcting the visual defect. Alternatively, surgical intervention is sometimes considered. This can even correct the astigmatism completely. Preventive measures have proven successful only in children. In them, therapy should begin early to prevent major refractive error in adulthood.
What you can do yourself
Since astigmatism is a condition caused by the growth of the eye itself, self-help measures are very limited. Only the squinting of the eyes can provide relief in acute cases. This reduces the incident light rays, which leads to a more focused incidence of the image. Overall, the disturbing light rays – i.e. those falling in the out-of-focus area – can be corrected in this way. However, this purely compensatory mechanism is not an adequate therapy and in some cases leads to asthenopia – various symptoms, such as headaches or eyelid pain, follow the constant strain on the eyes. In this respect, squinting the eyes cannot be recommended too frequently. It must be urgently advised against various eye therapies that have the goal of improvement. The benefit of techniques such as eye yoga or visual exercises has not been shown and is unlikely to be shown. The structural cause of astigmatism is not a muscular problem and therefore cannot be compensated by concentration and muscle exercises. Thus, the only remaining option is to compensate for astigmatism with appropriate visual aids or by surgical intervention.
