What is astigmatism? (Astigmatism explained)

The ability to see the world around us clearly is invaluable. But for many people, this is not a given. One of the most common visual disorders that can impair the visual experience is astigmatism.

In this article you will learn, among other things, what astigmatism is, what the symptoms of astigmatism are and what treatment options are currently available.

The anatomy of the eye: What is a corneal curvature?

The eye is a remarkable organ made up of several components that work together to focus incoming light and send visual signals to the brain. The outer layer of the eye is formed by the cornea, a clear, curved structure that acts like a lens to focus incoming light and project it onto the retina. The cornea is crucial for the refraction of light and plays an important role in focusing images onto the retina. An even curvature of the cornea is therefore crucial for clear and sharp vision.

A distinction is made between two “types of astigmatism”:

  • Regular astigmatism: With a regular astigmatism, the irregularity of the cornea is evenly distributed over the entire cornea. This form of curvature is often easier to correct and can be treated well with glasses or contact lenses as well as laser eye surgery.
  • Irregular astigmatism: In irregular astigmatism, the curvature of the cornea is unevenly distributed. This type of curvature is more common in certain eye conditions such as keratoconus or corneal scars and can be more difficult to treat. People with irregular astigmatism may need specially fitted contact lenses or refractive surgery.

Why is it harder to see with a curved cornea?

However, if the cornea is irregularly shaped, as is the case with a curvature, the light is not refracted correctly. This creates multiple focal points, resulting in distorted or blurred vision. People with astigmatism have difficulty seeing clear images, especially at a distance.

Corneal curvature symptoms at a glance:

The symptoms vary depending on the degree of curvature of the cornea and can vary in severity. Not all of the symptoms mentioned here are always present at the same time – even one or two of the problems described can indicate astigmatism:

  1. Blurred vision: People with astigmatism often experience blurred vision, especially for objects in the distance.
  2. Distortion or double vision: Due to the uneven refraction of light, people with astigmatism may see distorted or double images, especially when there is a strong contrast between light and dark areas.
  3. Eye strain or headaches: Straining the eyes to see clearly can lead to eye (over)strain, which can manifest itself as tiredness, burning or headaches. This eye strain is also known as asthenopia – symptoms also include burning eyes and dry eyes.
  4. Difficulty driving at night: People with astigmatism may have difficulty driving in low light conditions such as at night or in heavy rain. The irregular refraction of light can cause light sources such as vehicle headlights or streetlights to appear more scattered or blurred, which can impair vision.
  5. Eye rubbing or blinking: In an attempt to improve vision or soothe the eyes, people with astigmatism rub their eyes more often or blink more. However, this may provide a temporary feeling of relief, but in the long term it can exacerbate symptoms or cause irritation.

Diagnosis of astigmatism: keratometry, topography & autorefractometer

Corneal curvature is usually measured by an ophthalmologist or optician. There are various methods of measuring the curvature of the cornea, including

  • Keratometry: This is a commonly used method for measuring the radii of curvature of the cornea. A keratometer is a special instrument that is used to determine the refractive power of the cornea by measuring the reflections of rings or points of light on the cornea.
  • Topography: Corneal topography is a more advanced method of measuring the curvature of the cornea. It uses a special instrument that creates detailed “maps” of the corneal curvature. These maps show the exact shape of the cornea and can help to accurately diagnose and analyze corneal curvature.
  • Autorefractometer: An autorefractometer is a diagnostic instrument used to measure the refractive power of the eye. Although it is not specifically designed to measure corneal curvature, it can still give an indication of an irregular curvature of the cornea, which could indicate a curvature.

At EyeLaser, we can determine an existing astigmatism as part of our free suitability test and the non-binding preliminary examination and also determine the degree of astigmatism – whether regular or irregular astigmatism.

Astigmatism correction: How astigmatism can be treated

Thanks to modern medicine, anyone who suffers from astigmatism has various options for compensating or even permanently correcting defective vision. Instead of conventional visual aids, more and more people are opting for a one-off refractive procedure that permanently corrects astigmatism.

Laser eye surgery and lens surgery

Astigmatism correction with laser eye surgery always works according to the same principle. The structure of the cornea is changed so that it is regularly curved after the procedure. There are different methods to achieve this, all of which we offer at EyeLaser Vienna:

Which procedure is used depends on the severity and other personal factors. Together we will find the laser eye surgery that suits your eyes.

In addition to classic laser eye surgery, there is also the option of lens replacement or lens implantation. The natural lens is either removed(lens exchange) and replaced with a multifocal lens that compensates for the curvature or the natural lens is replaced with an artificial lens(lens implantation).

Glasses or contact lenses

Correcting astigmatism by wearing glasses or inserting contact lenses generally works equally well. Special toric lenses are used with glasses, although toric contact lenses are also available as an equivalent. These have a different refractive power in the vertical and horizontal directions in order to compensate for the irregular refraction of light by the curved cornea. Depending on the degree of curvature, it may be necessary for the glasses or lenses to be individually adjusted by an optician in order to precisely compensate for the curvature.

However, if you opt for this option, you will be dependent on wearing the visual aids for the rest of your life. This incurs ongoing costs, can be a nuisance in everyday life and can restrict your quality of life. Nevertheless, it is possible to correct visual defects with glasses and/or contact lenses.

Corneal transplantation

In severe cases of astigmatism that do not respond to other treatment methods, a corneal transplant may be considered. In this procedure, the affected cornea is replaced with a healthy cornea from a donor to restore vision.

However, this variant of treatment is the most invasive and costly. As a rule, correction using conventional treatment methods is more appropriate and more promising.

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Author:

Dr. Victor Derhartunian

Nachdem er sein Handwerk von den beiden Pionieren der Laserchirurgie gelernt hat, gehört Dr. Victor Derhartunian zu den führenden Augenlaser-Chirurgen. Er leitet die Praxis in Wien und kann seine Patienten in fünf Sprachen beraten.