Causes of Astigmatism

It is not known what causes astigmatism. Most often, astigmatism is present at birth or develops later in life and occurs when your eye’s front surface, the cornea, isn’t evenly curved. The cornea should curve evenly in all directions to focus light correctly on your retina — the back of your eye that processes images and sends them to your brain. 

Two Types of Astigmatism

There are two types of astigmatism: regular and irregular.

• Regular astigmatism is when your cornea or lens has a more curved or steep surface in one direction than another. Instead of being round in shape, it’s more like an oval. This type of astigmatism causes the vision to become blurry.

• Irregular astigmatism is less common and happens when your cornea is scarred from disease, an eye injury, previous eye surgery, or birth deformity. Unlike regular astigmatism, which affects the shape of the eye, irregular astigmatism affects the eye’s curvature.

Astigmatism With Refractive Errors

Astigmatism often occurs with other vision problems, such as nearsightedness or farsightedness. This is called a refractive error. A refractive error occurs when the eye cannot focus light correctly on the retina, resulting in blurred vision.

Nearsightedness (myopia) is when you can see things up close but not at a distance. This is caused when the eyeball is too long, or the cornea has too much curvature.

Farsightedness (hyperopia) is when you can see things at a distance but not up close. This is caused when the eyeball is too short, or the cornea does not have enough curvature.

Refractive Error Assessment

This measures how light bends (refracts) as it passes through your eye. There are three main types of refractive error assessments:

• Keratometry: A light is shone into your eye, and the doctor measures the curve of your cornea.
• Retinoscopy: The doctor shines a light into your eye and uses an instrument to assess the way your eye reflects the light.
• Subjective refraction: You sit in front of a machine called a phoropter, and the doctor shows you different lenses. They will ask you which lenses produce the clearest vision.

Astigmatism in Kids

Astigmatism is common in children. It is generally not a problem unless the astigmatism is severe or if your child also has another vision problem, such as nearsightedness or farsightedness. Most kids with astigmatism have a mild form and don’t even know it because they can see well enough not to need glasses. In fact, many young children with astigmatism don’t develop symptoms until they reach school age. 

Astigmatism vs. Lazy Eye

Lazy eye and astigmatism are two different conditions that can cause similar vision problems. Both can make it hard for your eyes to focus on objects at a distance. But they differ in how they affect your vision and what causes them.

• Astigmatism is caused by an imperfection in the curvature of your eye. 
• Lazy eye is caused by your brain not fully developing the vision in one eye. 
• Lazy eye can happen in one or both eyes. 

Symptoms

The symptoms of astigmatism can be different for everyone. You may not have any symptoms at all, or you may only notice symptoms occasionally. The most common symptom is blurry vision. Other symptoms can include:

• Eye fatigue
• Headaches
• Squinting
• Eye irritation

If you have any of these symptoms, make an appointment with us at Denver Youth Dental and Vision to get a complete eye exam. 

Can It Be Prevented?

There’s no known way to prevent astigmatism. But regular eye exams are a good way to check if you are starting to develop an eye condition.

Testing for Astigmatism

Eye Examination 

The only way to diagnose astigmatism is to get an exam from an eye doctor. During an eye examination for astigmatism, your doctor will:

• Evaluate your symptoms
• Conduct a visual acuity test to measure how well you see at various distances
• Do a refractive error assessment to determine if you have astigmatism or another vision problem.
• Check the condition of your eyes.

After the exam, your doctor will discuss the results and recommend treatment options. They may prescribe glasses, contact lenses, or refractive surgery if you have astigmatism.

Visual Acuity

This measures how well you see at various distances. The eye doctor will ask you to read a chart with progressively smaller letters from across the room.

Treatments for Astigmatism

The most common treatments for astigmatism are glasses, contact lenses, or refractive surgery. Which specific treatment will be best for you will be discussed by your doctor after diagnosis.

Eyeglasses

Corrective lenses are the most common treatment for astigmatism. They correct your vision by bending (refracting) the light entering your eyes. The eyeglass lenses have different curvatures, which helps focus the light correctly on your retina.

Contacts

Contact lenses are a popular alternative to glasses. They correct your vision by bending the light entering into your eyes. There are two main types of contact lenses for astigmatism:

• Hard contact lenses: These are made of a rigid, inflexible material. They correct your vision by aligning with the shape of your cornea.
• Soft contact lenses: These are made of a flexible material. They correct your vision by molding to the shape of your cornea.

Refractive Laser Surgery

Refractive surgery is a type of surgery done to correct your vision. There are several types of refractive surgery, including:

• LASIK (laser-assisted in situ keratomileusis) is the most common type of refractive surgery. It involves using a laser to make a thin flap in your cornea. The surgeon then uses the laser to remove tissue from your cornea to change its shape.
• PRK (photorefractive keratectomy) surgery is similar to LASIK, but no flap is made in the cornea. Instead, the surgeon uses the laser to remove tissue from the surface of your cornea to change its shape.
• RLE (refractive lens exchange) surgery is done when you have severe astigmatism. The surgeon removes your natural lens and replaces it with an artificial lens.
• ICL  (Implantable Collamer Lens) surgery is another option for people with severe astigmatism. A tiny lens is implanted permanently in your eye to help correct your vision.

Who Is at Risk

Different factors can increase your risk of astigmatism, including:

• Family history: if you have a family member with astigmatism, you’re more likely to have it.
• Age: children are more likely to develop astigmatism than adults.
• Nearsightedness or farsightedness: if you’re nearsighted or farsighted, you’re more likely to develop astigmatism.
• Corneal injury: if you’ve injured your cornea, you’re more likely to develop astigmatism.

Eye surgery: if you’ve had surgery on your eye, you’re more likely to develop astigmatism.