Astigmatism Meaning
Astigmatism meaning or Astigmatism definition can be explained as an optical imperfection that obscures the vision. Before realizing what causes this deformity, we first have to understand how the eye sees the light. When light enters a circular focal point (round like a ball), it refracts or twists, equitably. On the off chance that the focal point isn't circular or spherical, the light that enters the focal point is refracted more one direction than another. An unpredictably shaped cornea or lens keeps light from concentrating appropriately on the retina, the light-sensitive surface at the rear of the eye. Subsequently, vision gets obscured at any separation. This can prompt eye distress and cerebral pains.
Types of Astigmatism
The eye defect is usually brought about by a sporadically formed cornea or mutilated lens. At the point when the cornea has an irregular shape, what is said as corneal astigmatism meaning. At the point when the state of the lens is twisted, you have lenticular astigmatism. Because of either type, your vision for both close and far articles seem foggy or bent. It's practically similar to investigating a funhouse mirror in which you show excessively tall, excessively broad, or overly slender.
The steepest and flattest meridians of an eye with astigmatism are known as the vital or principal meridians.It can additionally be delegated regular astigmatism and irregular astigmatism as two types of astigmatism. Inconsistent, head meridians are opposite to one another (90-degree detachment). Inverse to this, irregular, the principal meridians are not different from one another.
Most astigmatism is regular astigmatism, a corneal, which gives the front surface of the eye a sporadically curvy shape, similar to that of a spoon. Eye wounds and injuries that bring about scars on the cornea can cause a sporadic deformity. Particular kinds of eye medical procedures or a sickness called keratoconus (continuous diminishing of the cornea) can likewise be one of the astigmatism causes.
Regular Astigmatism
Irregular cornea or lens bend of the eye causes regular astigmatism, which is one of the types of astigmatism. In this condition, the principal meridians are consistently separated by 90 degrees from one another. For this situation, there will be a back to back variety in the refractive force, starting with one meridian then onto the next. Every meridian in regular astigmatism has a smooth bend at each point over the passage of the understudy.
This is the most popular sort of astigmatism in which the manifestations included are hazy vision, cerebral pains, light affectability, and so forth.
Irregular Astigmatism
In irregular astigmatisms, which is one of the types of astigmatism, the principal meridians are isolated by any edge other than 90°, i.e., they are not opposed to one another. In this sort, the shape at every meridian isn't uniform; however, changes start with one point then onto the next over the pupil's passage.
Astigmatism Causes and Correction
Your eye has two structures with curved surfaces that twist (refract) light onto the retina, which makes the pictures.
The cornea, the away from the surface of your eye alongside the tear film
The focal point, a reasonable structure inside your eye that changes shape to help focus around close to objects.
In a formed eye, every one of these components has a round ebb and flow, similar to the outside of a smooth ball. A cornea and focal point with such an arch curve (refract) all approaching light similarly make a pointedly centered picture straightforwardly around the retina, at the rear of your eye.
We can correct Astigmatism by wearing eyeglasses, contact lenses, and Orthokeratology.
Solved Questions
Which Lens is Used in Astigmatism?
Lens used in Astigmatism is the toric lens, a soft contact lens which a doctor recommends.
Fun Facts
Astigmatism causes also seem to have a genetic component, which may be passed down to you from generation to generation.
Astigmatism can be hard to detect as one of the common symptoms of astigmatism is a blurry vision, which is so mild that hardly people recognize it.
Optometrist can easily detect Astigmatism with proper eye exam for measuring the eye’s ability to identify the details and errors.
FAQs on Astigmatism Eye Defects
1. What is astigmatism from a physics perspective?
From a physics standpoint, astigmatism is a type of refractive error where the eye cannot focus light into a single, sharp point on the retina. This occurs because the eye's cornea or lens has an irregular curvature, meaning it is shaped more like a rugby ball than a perfect sphere. As a result, light rays passing through different planes (meridians) of the eye are refracted differently and converge at multiple focal points, causing blurred or distorted vision.
2. What is the primary physical cause of astigmatism in the human eye?
The primary physical cause of astigmatism is a non-uniform curvature of the eye's refractive surfaces. This is most commonly found in the cornea (the eye's transparent outer layer), a condition known as corneal astigmatism. Less frequently, it can be caused by an irregularly shaped lens inside the eye, which is called lenticular astigmatism. In either case, the surface is not perfectly spherical, leading to different refractive powers along different axes.
3. How does astigmatism differ from myopia and hypermetropia?
Astigmatism differs fundamentally from myopia and hypermetropia in how it affects light focus. In myopia (nearsightedness) and hypermetropia (farsightedness), the eye's curvature is uniform, but the overall refractive power or eyeball length causes a single focal point to form either in front of or behind the retina. In contrast, astigmatism is caused by non-uniform curvature, resulting in multiple focal points. This means that instead of uniformly blurry vision, a person with astigmatism experiences distorted vision where lines in one direction might be clearer than lines in another.
4. What are the common symptoms that indicate an astigmatic eye defect?
The common symptoms that may indicate astigmatism are a direct result of the eye's inability to form a clear image. These include:
Blurred, distorted, or fuzzy vision at all distances.
Eyestrain or discomfort, particularly after reading or focusing for long periods.
Frequent headaches.
Difficulty with night vision, such as seeing halos around lights.
Squinting to try and see clearly.
5. How is astigmatism corrected using lenses as per the CBSE 2025-26 syllabus?
As per the CBSE syllabus, astigmatism is corrected using spectacles or contact lenses with a cylindrical lens. Unlike a spherical lens which has the same curvature in all directions, a cylindrical lens has curvature in only one axis. This special lens is oriented precisely to counteract the irregular curvature of the patient's cornea or lens. It adds or reduces refractive power only in the specific meridian that requires correction, allowing all light rays to once again converge at a single focal point on the retina.
6. Why is a cylindrical lens, and not a standard spherical lens, required to correct astigmatism?
A standard spherical lens, used for myopia or hypermetropia, refracts light equally in all directions because its curvature is uniform. This cannot correct astigmatism because the problem in an astigmatic eye is asymmetrical—the eye has different refractive powers in different planes. A cylindrical lens is required because it has refractive power in only one direction (along its axis). This allows an optometrist to add corrective power to the exact plane that is faulty, neutralising the eye's irregular refraction without affecting the plane that is already focusing correctly.
7. What are the two main types of astigmatism based on its location in the eye?
The two main types of astigmatism, based on where the irregularity occurs, are:
Corneal Astigmatism: This is the most common type, where the defect is caused by an imperfectly curved cornea. The cornea, instead of being dome-shaped, is toric (like a slice from the side of a donut).
Lenticular Astigmatism: This is a less common type where the defect is caused by an irregularity in the curvature of the eye's natural lens, which is located behind the cornea.
In both cases, the result is the same: light is not focused to a single point, leading to distorted vision.
8. How does having astigmatism affect a person's ability to see objects at different orientations?
A key effect of astigmatism is the inability to see lines at all orientations with equal clarity. Because the eye has different focal lengths for different meridians, a person with astigmatism might be able to see vertical lines clearly while horizontal lines appear blurry, or vice versa. For example, when looking at a plus sign (+), one bar might seem sharp and dark while the other looks faint and fuzzy. This selective blurring is a classic example of how astigmatism distorts vision, unlike the uniform blurriness of uncorrected myopia or hypermetropia.
