Astigmatism: A Closer Look

What is Astigmatism?

Astigmatism is a common, but much less understood type of refractive error (a condition of the eye that causes objects viewed by the eye to be out of focus). It is different from nearsightedness and farsightedness, the other more well-known refractive errors. In order to understand what it really is and how it affects our vision, we need to understand four concepts:
 

1. 1. Light Refraction: When light enters our eye, it bends (refracts) to focus at a certain point (the focal point). In an eye with no prescription (also called emmetropia or an eye with “perfect vision”), light focuses precisely on the back part of the eye called the retina (our eye sensors). When the focal point is precisely on the retina, the image is perfectly in focus and a clear image is sent to the brain.
    

2. 2. The Astigmatic Eye: Astigmatic eyes refract light in such a way that results in two focal points instead of one focal point like in myopia and hyperopia. Instead of having a perfectly spherical (like a basketball) shaped cornea (the clear, front part of the eye) like in myopia and hyperopia, individuals with astigmatism have a cornea that resembles a football. A football has a steeper curve and a flatter curve perpendicular from the steeper curve. This football shape creates the two focal points. It is impossible to naturally focus both points on the retina at the same time, so the image from both distant and near objects sent to the brain will be blurry.
    

3. 3. Accommodation: The action of the eye focusing light closer to the front of the eye is called accommodation. To do this, the muscles of the eye’s focusing system strain and cause light to bend at a steeper angle in the eye, which causes it to focus closer to the front of the eye. The only way for the eye to try to make images sharper is to try to accommodate. No amount of accommodation can perfectly focus both focal points on the retina, so the astigmatic eye is always blurry and constantly accommodates and strains to try to see clearer.
    

4. 4. Pinhole Effect: For the purposes of this article, the concept of the pinhole effect is that as the size of the hole through which light from an object enters the eye decreases, the object comes into better focus. This concept explains why people squint to see better when an image is blurry. The more they squint, the smaller the hole, the clearer the object. Squinting helps people see things more clearly, but it also causes strain on the eyelid and facial muscles responsible for squinting. This commonly leads to eyestrain and even headaches. This is why it is much more common for astigmatic eyes to experience eyestrain and blur for both far and near objects.

Symptoms and Everyday Challenges

1. 1. Blurry Distance and Near Vision: Seeing distant objects, driving, sports, and outdoor activities may be challenging due to blurred far vision. Reading a book, working on a computer, texting, or examining small details may be challenging due to blurred close-up vision. o While most people with moderate astigmatism know the benefits of having sharp vision, people with mild astigmatism may not realize how much going from mildly blurry, but manageable vision to sharp vision can make. For example, nighttime glare can be a nuisance and almost dangerous when driving. Many people with astigmatism who can legally drive without glasses wear prescription glasses at night because it can significantly decrease glare and help them drive more safely.
    

2. 2. Eyestrain and Headaches: Frequent eyestrain and headaches can occur from squinting and accommodating as the astigmatic eye tries to sharpen its vision. o Eyestrain can be considered a type of headache since it causes discomfort to the area around the eyes. While eyestrain can be considered a type of headache, it is important to differentiate between eyestrain and other headaches since eyestrain is not a medical emergency while some other types of headaches may be. Eyestrain also may lead to other headaches due to the amount of tension in facial muscles leading to pain in other parts of the head.
    

Causes and Risk Factors

1. 1. Genetics: Astigmatism tends to run in families. If a person’s parents or siblings have it, they are more likely to develop it.
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3. 2. Eye Shape: The shape of the cornea affects how light refracts. In astigmatism, the cornea has two different curvatures, which results in blur.

Corrective Measures

1. 1. Eyeglasses: Correctly prescribed glasses help to focus light onto the retina. This gives much needed relief from blur, eyestrain, and headaches. Glasses also allow patients to optimally enjoy tasks that rely on sharp and comfortable vision.
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3. 2. Contact Lenses: Correctly prescribed contact lenses also help to focus light onto the retina. They perform the same task as glasses while usually giving more comfort. Glasses for high amounts of astigmatism can be heavy and bulky. Contact lenses do not have any of these drawbacks.
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5. 3. Refractive Eye Surgery (LASIK/PRK/ICLs): If an astigmatic patient seeks a more permanent solution, laser surgeries such as LASIK and PRK reshape the cornea to improve focus. Implantation of an ICL improves focus by implanting a synthetic lens in front of the natural lens. There are pros and cons to each surgery, so consult an ophthalmologist to determine if you are a suitable candidate for any of these surgeries.

Monitoring and Lifestyle Tips

1. 1. Regular Eye Exams: Symptoms of astigmatism may subtly worsen over time. Routine eye exams help track changes and adjust prescriptions.
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3. 2. Good Lighting: Adequate lighting slightly reduces blur and may minimize the need for glasses and/or contact lenses.
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5. 3. Rest Your Eyes: Follow the 20-20-20 rule: Every 20 minutes, look at something 20 feet away for 20 seconds

How iCare Optometry Can Help

1. 1. Optimal Glasses/Contact Lens Prescriptions: Sharp vision is very important for most people and can help them better enjoy the world as well as function during important tasks. It is usually easy for an Optometrist to help someone see clearly, but clearly without eyestrain is a different story. If glasses are too strong, patients are usually able to see clearly, but have to strain to do so. Our Optometrist takes the time to make sure our patients’ vision is not only clear, but also comfortable.
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3. 2. Ideal Glasses Options: Glasses lenses for astigmatism become bulkier, heavier, and minifies the patient’s eyes the more the prescription increases. High Index lens material and/or smaller frames may be recommended to reduce the inconvenience of these issues.
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5. 3. Refractive Eye Surgery Information: Taking into account the magnitude of the prescription, patient age, and patient goals, we can provide personalized information to help our patients decide if seeing an Ophthalmologist for refractive surgery is the best course of action. We can also go into more detail on the differences between LASIK, PRK, and ICLs.
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7. 4. Ruling Out Eyestrain: Some patients with chronic headaches are referred to us by their primary care providers (PCPs) to rule out more benign causes of headaches such as blur. Before more costly and invasive procedures such as MRIs and CT scans are performed, most PCPs and patients want to see if simple glasses and/or contacts can alleviate headaches. We have helped many patients resolve their headaches caused by eyestrain with our glasses and contact lens prescriptions.

For more information on astigmatism, please visit iCare Optometry at our office in Idaho Falls, Idaho. We work with our patients to understand their visual needs and help them in the best way possible. Please call (208) 522-2839 to discuss any questions with our team of experts or to schedule an appointment today