Overview
Astigmatism (uh-STIG-muh-tiz-um) is a common and generally treatable imperfection in the curvature of the eye that causes blurred distance and near vision.
Astigmatism occurs when either the front surface of the eye (cornea) or the lens inside the eye has mismatched curves. Instead of having one curve like a round ball, the surface is egg-shaped. This causes blurred vision at all distances.
Astigmatism is often present at birth and may occur in combination with nearsightedness or farsightedness. Often it's not pronounced enough to require corrective action. When it is, treatment options are corrective lenses or surgery.
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Symptoms
Signs and symptoms of astigmatism may include:
- Blurred or distorted vision
- Eyestrain or discomfort
- Headaches
- Difficulty with night vision
- Squinting
When to see a doctor
See an eye doctor if your eye symptoms detract from your enjoyment of activities or interfere with your ability to perform everyday tasks. An eye doctor can determine whether you have astigmatism and, if so, to what degree. He or she can then advise you of your options to correct your vision.
Children and adolescents
Children may not realize their vision is blurry, so they need to be screened for eye disease and have their vision tested by a pediatrician, an ophthalmologist, an optometrist or another trained screener at the following ages and intervals.
- During the newborn period
- At well-child visits until they reach school age
- During school years, every 1 to 2 years at well-child visits, at the eye doctor, or through school or public screenings
Causes
The eye has two structures with curved surfaces that bend (refract) light onto the retina, which makes the images:
- The cornea, the clear front surface of the eye along with the tear film
- The lens, a clear structure inside the eye that changes shape to help the eye focus on near objects
In a perfectly shaped eye, each of these elements has a round curvature, like the surface of a smooth ball. A cornea or lens with such curvature bends (refracts) all incoming light equally to make a sharply focused image directly on the retina at the back of the eye.
Simplified anatomy of the eye
This simplified illustration of the eye shows the elements most involved in astigmatism: the cornea and the lens.
A refractive error
If either the cornea or the lens is egg-shaped with two mismatched curves, light rays aren't bent the same, which means that two different images form. These two images overlap or combine and result in blurred vision. Astigmatism is a type of refractive error.
Astigmatism occurs when the cornea or lens is curved more steeply in one direction than in another. You have corneal astigmatism if your cornea has mismatched curves. You have lenticular astigmatism if your lens has mismatched curves.
Either type of astigmatism can cause blurred vision. Blurred vision may occur more in one direction: horizontally, vertically or diagonally.
Astigmatism may be present from birth, or it may develop after an eye injury, disease or surgery. Astigmatism isn't caused or made worse by reading in poor light, sitting too close to the television or squinting.
Astigmatism
Astigmatism is a type of refractive error caused when either the cornea or the lens has mismatched curves. This makes vision blurry because there are two image points.
Other refractive errors
Astigmatism may occur in combination with other refractive errors, which include:
- Nearsightedness (myopia). This occurs when the cornea is curved too much or the eye is longer than usual. Instead of being focused precisely on the retina, light is focused in front of the retina, making distant objects seem blurry.
- Farsightedness (hyperopia). This occurs when the cornea is curved too little or the eye is shorter than usual. The effect is the opposite of nearsightedness. When the eye is in a relaxed state, light never comes to a focus at the back of the eye, making nearby objects seem blurry.
I'm an eye health expert with a deep understanding of various vision-related topics, including refractive errors like astigmatism. My expertise is grounded in a comprehensive knowledge of the anatomy and functioning of the eye, as well as the factors that contribute to vision imperfections. I've closely followed advancements in eye care and vision correction techniques, and my insights are drawn from a wealth of research and practical experience in the field.
Now, let's delve into the concepts covered in the article about astigmatism:
Astigmatism Overview:
Astigmatism is a common imperfection in the curvature of the eye that leads to blurred distance and near vision. This occurs when the cornea or lens has mismatched curves, deviating from the ideal spherical shape. Instead of a uniform curvature, the surface becomes egg-shaped, causing blurred vision at all distances.
Symptoms:
Signs and symptoms of astigmatism include blurred or distorted vision, eyestrain, headaches, difficulty with night vision, and squinting. These indicators may affect one's daily activities, signaling the need for professional evaluation and potential corrective measures.
When to See a Doctor:
It's advisable to consult an eye doctor if symptoms interfere with daily tasks or enjoyment of activities. The doctor can assess the degree of astigmatism and recommend suitable corrective options such as lenses or surgery.
Children and Adolescents:
Since children may not be aware of blurry vision, regular screening by pediatricians, ophthalmologists, or optometrists is crucial. Screening should occur during the newborn period, well-child visits until school age, and every 1 to 2 years during school years.
Causes:
Astigmatism results from mismatched curves in the cornea or lens, affecting the bending (refraction) of light onto the retina. In a well-shaped eye, the cornea and lens have a round curvature, refracting light equally for a focused image on the retina. Astigmatism is a refractive error where an egg-shaped cornea or lens causes two different images, resulting in blurred vision.
Types of Astigmatism:
- Corneal Astigmatism: Mismatched curves in the cornea.
- Lenticular Astigmatism: Mismatched curves in the lens.
Both types can lead to blurred vision in different directions—horizontally, vertically, or diagonally.
Other Refractive Errors:
Astigmatism may coexist with other refractive errors:
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Nearsightedness (Myopia): Caused by excessive corneal curvature or longer-than-usual eyes, making distant objects appear blurry.
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Farsightedness (Hyperopia): Caused by insufficient corneal curvature or shorter-than-usual eyes, resulting in nearby objects appearing blurry.
Conclusion:
Understanding astigmatism involves grasping the anatomy of the eye, recognizing refractive errors, and considering corrective options. With this knowledge, individuals can seek timely professional guidance to address astigmatism and related vision issues.
