Astigmatism – symptoms, treatment, causes

Millions of people have trouble performing daily tasks, working, and studying due to vision disorders. While most people have basic knowledge about myopia and hyperopia, astigmatism – despite being quite common – remains a mystery. In this article, we will explain its causes, symptoms, and treatment.

What is Astigmatism?

Astigmatism is a vision defect that occurs as a result of an irregular shape of the cornea or lens of the eye. This causes the image not to focus properly on the retina, leading to blurred vision both up close and at a distance. People with astigmatism often see objects as stretched or deformed.

Astigmatism – Causes

Uneven curvature of the cornea or lens is responsible for astigmatism. What does this mean? In myopia or hyperopia, the eye is elongated or shortened, but symmetrical. For this reason, the image is formed in front of or behind the retina, but remains "upright." However, in the case of astigmatism, the cornea or lens has an irregular, asymmetrical shape (resembling an egg cut lengthwise). This causes the image, although formed on the retina, to be stretched, as if tilted, and consequently – blurry. People with significant astigmatism see a tilted ellipse instead of a circle, and a parallelogram instead of a square.

However, in many cases, minor astigmatism has little or no effect on visual acuity. It is estimated that this disorder affects 40% of the population and is hereditary. Half of children are born with this condition, which, however, disappears as the body develops. Of this group, only 20% of toddlers will require treatment. In healthy children, there is little chance that astigmatism will appear later in life, but it is worth remembering that this defect can develop, for example, after eye surgery or injury. Diseases that directly or indirectly affect the shape of the cornea also contribute to it.

Astigmatism – Symptoms

Unlike people who are myopic or hyperopic, astigmatism causes objects both up close and far away to appear blurry. Objects and planes are warped and distorted. For this reason, a person with astigmatism:

• has impaired spatial perception – it is difficult for them to judge the distance to an object and they may accidentally bump into it,
• sees worse at dusk and at night and is sensitive to the light from lamps and cars,
• has difficulty concentrating on studying and reading,
• often squints, which can lead to frequent eye and head pain.

In children, astigmatism can be suspected if they frequently squint and rub their eyes or bring toys close to their faces.

The symptoms are more or less bothersome depending on the severity of astigmatism, however, the defect does not tend to worsen with age. Usually, up to the age of 40, it intensifies to a small extent or not at all, and between the ages of 40 and 80, the average change in astigmatism is around 1.00 D. Of course, every case is different, which is why regular eye examinations are recommended.

Untreated astigmatism leads not only to a worsening of the defect, which negatively affects the quality of life, but also to inflammation of the eyeball and other eye-related complications. In children, it affects academic performance and can easily be mistaken for dyslexia. Therefore, even with minor symptoms, it is worth visiting an ophthalmologist or optometrist. Astigmatism can be diagnosed through skiascopy or refraction examination or using a special Amsler grid. These tests allow for the determination of the type and magnitude of the defect.

Astigmatism – Treatment

Astigmatism is not a disease, so it cannot be cured. It is corrected with special cylindrical lenses adapted to the degree and type of defect.

Regular astigmatism (the most common) is when one plane of the cornea is more curved than the other. The magnitude of the defect is determined based on the difference in refractive power between the two principal meridians, which are at right angles to each other.

There are 3 types:

• Simple regular astigmatism (with the rule) – the principal meridian is in the range of 60°-120°. It causes greater refraction of light vertically.
• Compound regular astigmatism (against the rule) – the principal meridian is in the range of 30°-150°. It causes greater refraction of light horizontally.
• Oblique regular astigmatism – the principal meridian is in the range of 31°-59° or 121°-149°.

For the correction of simple astigmatism, glasses and contact lenses with toric lenses are recommended – they have a thicker layer at the bottom than at the top.

Irregular astigmatism is diagnosed when there are no principal meridians intersecting at a right angle, or there are more than two. It is rare because it is usually a consequence of an eye injury with irregular corneal damage. It also results from an eye disease in which the central part of the cornea becomes thinner and takes on an irregular shape. In such a situation, a specialist must select lenses for the individual curvature of the eye's surface.

For individuals over 21 years of age with a stable refractive error, laser vision correction is also performed. Pre-qualification by an ophthalmologist is required.