Astigmatism: Causes, Symptoms and Treatment

Astigmatism is a common refractive error in the eyes that causes blurred or distorted vision. This condition occurs when the cornea (the clear, dome-shaped front surface of the eye) or lens inside the eye has an irregular shape. Rather than being perfectly round, the cornea or lens is more oval, which leads to light being focused unevenly on the retina at the back of the eye. In this article, we’ll explore everything you need to know about astigmatism, including its causes, symptoms, treatment options and how to manage it effectively.

What is Astigmatism?

Astigmatism is a condition in which the eye doesn’t focus light properly due to an irregular curvature of the cornea or lens. The cornea is typically round like a basketball, but in someone with astigmatism, it is shaped more like a football, causing light to focus on multiple points rather than a single point on the retina. This leads to blurred or distorted vision at both near and far distances.

Types of Astigmatism:

• Corneal Astigmatism: When the cornea is unevenly shaped, leading to astigmatism.
• Lenticular Astigmatism: When the lens inside the eye has an irregular curvature.
• Mixed Astigmatism: A combination of corneal and lenticular astigmatism, where both parts of the eye contribute to the distortion.

Causes of Astigmatism

The primary cause of astigmatism is genetic. If one or both parents have astigmatism, it is more likely that their children will develop it as well. However, there are other factors that may contribute to the development or worsening of astigmatism over time:

1. Irregular Corneal Shape:

When the cornea is shaped like a football instead of a round ball, light is refracted improperly, causing blurry or distorted vision. This is the most common cause of astigmatism.

2. Irregular Lens Shape:

The lens inside the eye can also be irregularly shaped, which may cause lenticular astigmatism. This type is less common than corneal astigmatism but can still significantly affect vision.

3. Eye Injury or Surgery:

Trauma to the eye or surgical procedures such as cataract surgery can lead to changes in the shape of the cornea or lens, resulting in astigmatism.

4. Keratoconus:

Keratoconus is a progressive condition in which the cornea thins and becomes more conical, leading to astigmatism. This condition can worsen over time and may require more intensive treatment.

5. Other Eye Diseases:

Conditions like pterygium (growths on the cornea) or scarring from past infections can also lead to corneal astigmatism.

6. Age-Related Changes:

As people age, changes in the lens and cornea can lead to the development of astigmatism, even if they didn’t have it earlier in life.

Symptoms of Astigmatism

The severity of astigmatism can vary, with some people experiencing only mild symptoms, while others may find it significantly impacts their daily life. Common symptoms of astigmatism include:

1. Blurred or Distorted Vision: One of the most noticeable signs of astigmatism is blurred or distorted vision at all distances. Whether the object is near or far, it may appear stretched or wavy.
2. Eye Strain: People with astigmatism often experience eye strain from trying to focus. This can lead to discomfort after activities like reading or using a computer for extended periods.
3. Frequent Headaches: Astigmatism can cause eyestrain, which often results in headaches, particularly after reading or other visual tasks.
4. Squinting: Those with astigmatism may squint often in an attempt to bring things into clearer focus, which can worsen eye strain and fatigue.
5. Double Vision: Severe astigmatism can lead to double vision, especially when trying to focus on detailed objects like text or small objects.
6. Night Vision Problems: Astigmatism can make it difficult to see clearly at night or in low-light conditions. People with astigmatism often report halos or glare around lights.

If you experience any of these symptoms, it’s essential to see an eye care professional for a proper diagnosis and treatment plan.

Diagnosing Astigmatism

To diagnose astigmatism, eye care professionals use a variety of tests during a comprehensive eye exam:

1. Visual Acuity Test: This test measures how well you can see at various distances. If your vision is blurry or distorted, it may indicate astigmatism.
2. Keratometry: A keratometer measures the curvature of your cornea. This test helps determine the amount of astigmatism present and is essential for creating a prescription for glasses or contact lenses.
3. Corneal Topography: This test provides a detailed map of the surface of the cornea, helping to detect irregularities that could indicate astigmatism. It’s especially useful for people with more severe or irregular astigmatism.
4. Refraction Test: This is a common test where an optometrist uses a machine called a phoropter to determine the prescription for glasses or contacts, which can correct astigmatism.

Types of Astigmatism

Astigmatism is classified into different types based on its orientation and severity:

1. Regular Astigmatism:

In regular astigmatism, the principal meridians (the flattest and steepest parts of the cornea) are perpendicular to each other. This is the most common form and is easier to correct with glasses or contacts.

2. Irregular Astigmatism:

In irregular astigmatism, the principal meridians are not perpendicular, or the curvature of the cornea is uneven in more than one direction. This type of astigmatism is more challenging to treat and often requires special lenses or surgery.

3. With-the-Rule Astigmatism:

In with-the-rule astigmatism, the vertical meridian is more curved than the horizontal meridian. This type of astigmatism is most common in younger people.

4. Against-the-Rule Astigmatism:

In against-the-rule astigmatism, the horizontal meridian is more curved than the vertical meridian. It is more commonly seen in older individuals.

5. Mixed Astigmatism:

In mixed astigmatism, one meridian is nearsighted (myopic) and the other is farsighted (hyperopic). This form of astigmatism requires a special prescription for each meridian.

Treatment for Astigmatism

While astigmatism cannot be “cured,” there are several effective treatment options to correct or manage the condition:

1. Eyeglasses:

Prescription glasses are the most common and simplest way to correct astigmatism. Special cylindrical lenses are used to compensate for the irregular shape of the cornea or lens, providing clear vision.

2. Contact Lenses:

For people with astigmatism, there are several types of contact lenses available:

• Toric Lenses: These lenses are specifically designed to correct astigmatism by having different curvatures in different parts of the lens.
• Rigid Gas Permeable (RGP) Lenses: These lenses can help reshape the cornea over time and may provide better vision for people with astigmatism.
• Scleral Lenses: Larger lenses that rest on the white part of the eye, scleral lenses are often used to treat more severe or irregular astigmatism.

3. Refractive Surgery:

Laser surgery options such as LASIK, PRK and LASEK can permanently reshape the cornea and correct astigmatism. These procedures can reduce or eliminate the need for glasses or contacts. such as

• LASIK: LASIK (Laser-Assisted In Situ Keratomileusis) is a popular surgical procedure that uses lasers to reshape the cornea and correct astigmatism. It can provide permanent results for many people.
• PRK (Photorefractive Keratectomy): PRK is another laser eye surgery similar to LASIK, but it involves reshaping the cornea’s surface rather than creating a flap in the cornea.
• LASEK: This is a variation of PRK where the corneal surface is loosened with an alcohol solution before being reshaped.
• Astigmatic Keratotomy (AK): This surgical procedure involves making incisions in the cornea to correct astigmatism by altering its shape.

4. Orthokeratology (Ortho-K):

Ortho-K involves wearing special rigid contact lenses overnight to reshape the cornea temporarily. This non-surgical method can help improve vision during the day for people with mild to moderate astigmatism.

Preventing Astigmatism

Since astigmatism is usually inherited, there’s no guaranteed way to prevent it. However, maintaining regular eye exams is essential for early detection. Astigmatism can worsen over time, so it’s important to monitor changes in your vision and seek corrective treatment as needed.

Astigmatism is a common but treatable condition that can cause blurred or distorted vision. While astigmatism is often inherited, it can also develop due to injury, surgery, or age. Fortunately, astigmatism can be effectively managed with glasses, contact lenses, or surgery, helping individuals to see clearly and lead normal, active lives. Regular eye

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