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.
As an ophthalmology enthusiast with a deep understanding of visual imperfections, particularly astigmatism, I aim to provide comprehensive insights into this common condition. My knowledge is rooted in both theoretical understanding and practical experience, having engaged with the latest research, clinical practices, and patient interactions.
Astigmatism Overview:
Astigmatism is a prevalent and usually correctable irregularity in the eye's curvature, leading to blurred vision at various distances. The primary cause lies in the misshapen curvature of either the cornea or the lens, deviating from the normal spherical form to an egg-shaped structure. This deviation results in distorted vision, affecting both near and far distances.
Symptoms:
Recognizing the signs of astigmatism is crucial for seeking timely intervention. Symptoms include blurred or distorted vision, eyestrain, headaches, difficulty with night vision, and squinting. These indicators should prompt individuals to consult an eye doctor if they impact daily activities or diminish overall visual enjoyment.
When to See a Doctor:
Consultation with an eye care professional is recommended if astigmatism symptoms affect daily life. The degree of astigmatism can be assessed, and appropriate corrective measures, such as lenses or surgery, can be suggested based on individual needs.
Children and Adolescents:
Given that children may not be aware of blurry vision, regular screenings by pediatricians, ophthalmologists, or trained screeners are essential during the newborn period, well-child visits until school age, and every 1 to 2 years during the school years.
Causes:
Astigmatism results from the mismatched curves of the cornea or lens, affecting the refraction of light onto the retina. In a perfectly shaped eye, light is refracted uniformly, creating a sharply focused image on the retina. However, with astigmatism, the mismatched curves create two different images that overlap, leading to blurred vision.
Types of Astigmatism:
There are two main types of astigmatism: corneal astigmatism and lenticular astigmatism. Corneal astigmatism involves mismatched curves in the cornea, while lenticular astigmatism occurs when the lens has mismatched curves. Both types result in blurred vision, and the direction of blurriness may vary—horizontally, vertically, or diagonally.
Development and Aggravating Factors:
Astigmatism may be present at birth or develop after an eye injury, disease, or surgery. Importantly, common activities such as reading in poor light, sitting too close to the television, or squinting are not causative factors.
Other Refractive Errors:
Astigmatism can coexist with other refractive errors, including nearsightedness (myopia) and farsightedness (hyperopia). Myopia involves the cornea being curved too much or the eye being longer than usual, resulting in blurred distance vision. Hyperopia, on the other hand, occurs when the cornea is curved too little or the eye is shorter than usual, causing nearby objects to appear blurry.
In summary, astigmatism is a multifaceted condition, and its understanding is crucial for timely detection and effective management. If you or someone you know is experiencing visual symptoms, seeking professional eye care is paramount to ensuring optimal vision and overall eye health.
