Corneal Curvature – Everything you need to know about astigmatism
A corneal curvature (medical: astigmatism, also called intentionality) occurs when the cornea of the eye does not have a uniform, spherical curvature, but a slightly oval or irregular shape. As a result, the eye does not focus light in a single point on the retina, resulting in blurred or distorted vision, both near and far.
Corneal curvature is one of the most common visual defects worldwide1 and affects people of all ages. Many sufferers do not know for years that their visual impairment has a clearly measurable cause. Typical complaints are blurred vision, headaches and rapid eye fatigue, especially with prolonged reading or screen work.
On this page you will get a complete overview: What exactly is a corneal curvature, what causes it, how is it measured and what treatment options are available? For each aspect, you will find an introduction here as well as the link to the in-depth article.
What is a corneal curvature? A definition
Corneal curvature, also known as astigmatism, is a common ametropia in which the cornea (or sometimes the lens of the eye) is not evenly curved.
This irregular curvature means that the light that falls into the eye is not correctly focused on a single point on the retina. Instead, multiple focal points or distorted lines appear on the retina, resulting in blurred or distorted vision. Therefore, astigmatism also has its name – this comes from Greek and can be translated as “pointlessness”.
The curvature of the cornea can be in different forms, from mild to severe, and affects both near and distant vision. Astigmatism often occurs together with other visual defects such as nearsightedness (myopia) or farsightedness (hyperopia) 2. In the international classification system ICD, astigmatism is listed under the code H52.2 and can be corrected by glasses, contact lenses or surgical procedures such as laser eye surgery.
Astigmatism is listed in the international classification system under ICD code H52.23.
Types of Astigmatism
Astigmatism occurs in various forms, depending on the way the light is refracted through the eye.
The most common type is regular astigmatism, in which the curvature of the cornea is different in two main meridians perpendicular to each other. This shape can be easily corrected with glasses or toric contact lenses, as the deviations are even.
Another variant is irregular astigmatism, which is caused by an uneven curvature of the corneal surface, often caused by scars or diseases such as keratoconus. Even with irregular astigmatism, the refraction of light is irregular, which makes correction more difficult. Special hard contact lenses or even surgical procedures are often necessary to compensate for visual impairment.
An ophthalmologist can determine not only whether a corneal curvature is present, but also what type of astigmatism it is. Accordingly, he will go through the treatment options with you and provide you with comprehensive advice.
Corneal curvature, nearsightedness and farsightedness – differences at a glance
Corneal curvature, nearsightedness and farsightedness are all common visual defects that affect vision in different ways. In the case of corneal curvature (astigmatism), the curvature of the cornea of the eye or the lens of the eye is irregular, as a result of which the light strikes the retina at several focal points. This results in blurred or distorted vision at all distances as the eye cannot evenly focus the light.
Short-sightedness (myopia), on the other hand, is a defective vision in which distant objects appear blurred. This is because the eye is either too long or the refractive power of the cornea is too strong, focusing the light in front of the retina. People with nearsightedness have difficulty seeing things clearly in the distance, while nearby objects remain clearly visible.
Farsightedness (hyperopia) is the opposite of nearsightedness. With this refractive error, the eyeball is often too short or the refractive power of the cornea too weak, so that incident light rays are focused behind the retinal plane. This causes nearby objects to appear blurry, while the view of distant objects is often unimpaired. Farsightedness may also become more pronounced with age (presbyopia), as the eye’s ability to focus on nearby objects decreases.
Corneal curvature often occurs together with another defective vision – nearsightedness or farsightedness. Nevertheless, astigmatism must be considered and treated as an independent defective vision.
Risk factors: Possible causes of corneal curvature?
A corneal curvature is usually congenital: the cornea does not grow uniformly round, but slightly oval (a genetic predisposition that cannot be prevented). In addition, there are acquired causes that can change the shape of the cornea in the course of life:
All risk factors and what they mean for your treatment can be found under the causes of corneal curvature.
Typical symptoms of a corneal curvature
Blurred vision near and far, distorted lines, headaches after prolonged reading or screen work4: Many sufferers attribute these complaints to fatigue for years, not to their defective vision. Added to this are glare sensitivity and poorer visual quality in the dark, especially when driving. The symptoms can vary greatly depending on the severity and often occur together with nearsightedness or farsightedness.
What which symptom means and when an ophthalmologist visit makes sense, read about the symptoms of corneal curvature.
Diagnosis: As the ophthalmologist determines astigmatism
A corneal curvature is reliably detected by the ophthalmologist through several examinations. First, the doctor checks the visual acuity, followed by a refraction measurement with the phoropter, which determines the exact refractive error of the eye.
For a precise measurement of the corneal surface, ophthalmometry or corneal topography 2 is also used (especially important if laser treatment is an option). The result shows the degree and axis of the curvature and forms the basis for the optimal correction.
Severity of astigmatism
Not every corneal curvature is equally pronounced. Clinically, a rough distinction is made between three levels:¹
- Mild astigmatism (below 1.00 diopter): Often no noticeable complaints, correction is not always necessary.
- Clinically relevant astigmatism (from 1.00 diopter): Measurable impairment of visual acuity and quality of life, correction through glasses, contact lenses or lasers is recommended.
- Severe astigmatism (from 2.00 dioptres): More intensive measures such as toric contact lenses or laser treatment are usually necessary.
¹ Wang et al. (2018): Influence of severity and types of astigmatism on visual acuity in school-aged children. Int J Ophthalmol.
You can find out what values your eyeglass prescription shows and what they mean in the corneal curvature values.
Treatment of a corneal curvature
Today, a corneal curvature can be reliably corrected. The most common methods are glasses with cylindrical lenses and toric contact lenses, which optically compensate for the irregular corneal curvature. Modern laser procedures such as SMILE® Pro or Femto-LASIK, which precisely reshape the cornea, are suitable for a permanent solution without a visual aid. Which method is individually suitable depends on the severity of the astigmatism, the thickness of the cornea and other factors.
All options in comparison can be found in the article on the treatment of corneal curvature.
Laser treatments for corneal curvature in Bányai Neue Augen
Bányai Neue Augen in Stuttgart and Karlsruhe offers modern and proven methods for correcting corneal curvature (astigmatism). Leading procedures include Femto-LASIK and SMILE® Pro, both of which provide precise and gentle solutions to permanently correct the curvature of the cornea.
The Femto-LASIK method is particularly suitable for patients with corneal curvature, as it models the cornea in a targeted and controlled manner. This procedure makes it possible to refocus the light correctly on the retina, which leads to a significant improvement in the quality of vision. At Bányai Neue Augen, this method is carried out using state-of-the-art laser technology to ensure maximum safety and efficiency.
SMILE® Pro offers a minimally invasive method and is also suitable for patients with dry eyes or thin corneas. This procedure is gentler because only a small access to the cornea is required. Both methods allow for quick recovery and provide long-term results.
In addition, Bányai Neue Augen also offers the option of artificial lenses. These toric lenses replace the natural lens of the eye and correct not only astigmatism, but also other visual defects such as farsightedness or presbyopia. And an A-PRK treatment can also be carried out – as part of a preliminary examination, we can find the ideal procedure for you.
Thanks to our many years of experience and the use of state-of-the-art technologies, we ensure that each treatment is individually adapted to achieve the best possible result for each patient.
FAQs on corneal curvature (astigmatism)
Corneal curvature can be treated in several ways. The most common methods are wearing glasses with cylindrical lenses or toric contact lenses that compensate for the irregular curvature of the cornea. For a permanent solution, laser treatment such as femto-LASIK or SMILE® PRO can also be considered to correct the cornea in a targeted manner.
With a corneal curvature, the light is not properly focused due to the uneven curvature of the cornea, resulting in blurred or distorted vision. This refractive error can affect both near and far vision and usually requires correction by visual aids or laser treatment.
With a corneal curvature, the light is not properly focused due to the uneven curvature of the cornea, resulting in blurred or distorted vision. This refractive error can affect both near and far vision and usually requires correction by visual aids or laser treatment.
If a corneal curvature is not corrected, it can lead to permanent problems such as chronic headaches, constant eye strain and deterioration of vision. Especially in children, an unrecognized and untreated corneal curvature can lead to weakness (amblyopia), in which one eye permanently sees worse than the other.
Yes, astigmatism and corneal curvature denote the same defective vision. The medical term astigmatism comes from Greek and describes the irregular curvature of the cornea, which prevents light from being focused at a point on the retina. In German-speaking countries, the terms corneal curvature and intentionality are also common.
Congenital corneal curvature usually remains stable in adult life, but can still change slightly during puberty. However, in certain corneal diseases, such as keratoconus, the curvature may progress. Regular check-ups with the ophthalmologist help to detect a change at an early stage and to act in a timely manner.
Whether a correction makes sense depends not only on the measured value, but also on whether complaints are present. Mild astigmatism below 1.00 diopters often causes no noticeable limitations. From 1.00 dioptres, the curvature is considered clinically relevant and correction through glasses, contact lenses or lasers may be indicated. You can find out what the values on your eyeglass prescription mean in the corneal curvature values.
Modern laser procedures such as SMILE® Pro or femto-LASIK can permanently correct a corneal curvature by precisely reshaping the cornea. Glasses and contact lenses visually compensate for the defective vision, but do not change the cornea itself. An individual preliminary examination will determine whether a laser procedure is suitable for you. All options can be found in the article on the treatment of corneal curvature.
In children, a corneal curvature is often detected late because they get used to blurred vision and do not express any complaints. If left untreated, it can impair vision development and lead to lazy vision (amblyopia). Regular eye examinations in childhood are therefore particularly important. The correction is usually carried out with special lenses.
References
1 Hashemi H et al. (2018): Global and regional estimates of prevalence of refractive errors: Systematic review and meta-analysis. Journal of Current Ophthalmology, 30(1):3-22.
2 Gurnani B, Kaur K (2022): Astigmatism. StatPearls, Treasure Island (FL): StatPearls Publishing.
3 Federal Ministry of Health: ICD code H52.2 – Astigmatismus. gesund.bund.de.
4 Read SA, Vincent SJ, Collins MJ (2014): The visual and functional impacts of astigmatism and its clinical management. Ophthalmic and Physiological Optics, 34(3):267-294.
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