About Astigmatism
The two main causes of astigmatism are irregularities in the cornea and the crystalline lens.
Root causes:
- Refractive astigmatism: This includes all the factors that cause astigmatism, such as irregularities in the shape of the cornea (the clear front layer of the eye) or the lens inside the eye. It explains how light is bent unevenly as it enters the eye, causing blurry vision.
- Corneal astigmatism: This refers specifically to irregularities in the shape of the cornea, which is the most common cause of moderate to high astigmatism. The cornea’s uneven shape bends light in multiple directions, making it harder for the eye to focus properly.
Non-modifiable risk factors for astigmatism are factors that cannot be changed or controlled. This includes:
- Genetic factors: Family and twin studies have shown that genetic factors play a role in the development of corneal and refractive astigmatism. It is estimated that about 50-65% of astigmatism may be inherited.
Modifiable risk factors for astigmatism are factors that can be influenced or changed. These include:
- Maternal smoking during pregnancy: Studies suggest that maternal smoking during pregnancy may be a risk factor for astigmatism.
- Ethnicity: Certain ethnicities, such as Hispanic, African American, and Asian races, have been associated with an increased risk of astigmatism.
- Iris color: Darker iris color (the colored part of the eye) has been identified as a potential modifiable risk factor for astigmatism.
It's important to note that these risk factors may vary in their impact on individual cases. It's always best to consult with your healthcare professional for personalized advice and guidance.
The most common early symptoms of astigmatism include:
- Blurred or distorted vision at all distances
- Headaches
- Squinting in order to see clearly
- Eyestrain, especially when the eye has to focus for long periods
- Difficulty seeing or driving at night
As astigmatism progresses or becomes more severe, other common symptoms may occur, such as:
- Increased blurry vision
- Increased eyestrain
- Needing to squint more frequently to see clearly
- More frequent headaches
- Difficulty seeing objects or reading small print up close
It's important to note that these symptoms may vary from person to person and can be influenced by other factors such as the presence of myopia (nearsightedness) or hyperopia (farsightedness). If you experience any of these symptoms, it is advisable to have an eye exam to determine the cause and receive appropriate treatment.
To diagnose astigmatism, eye specialists commonly perform the following examinations, tests, and procedures:
- Visual acuity test: This test measures how well a person can read letters or characters at a distance. It involves reading lines of letters on a chart, with the letters becoming progressively smaller on each line.
- Keratometry: A keratometer measures how light reflects off the surface of the cornea. This helps determine the shape and curvature of the cornea.
- Corneal topography: Corneal topography is an imaging technology that creates detailed maps of the cornea. It provides a more thorough assessment of the cornea’s shape and surface compared to a keratometer.
- Refraction test: A general test used to diagnose refractive errors like astigmatism, nearsightedness, and farsightedness. It involves placing lenses in front of the eyes to determine how light is focused
Additional examinations, tests, and procedures may be performed to assess the degree of astigmatism and its impact on vision. These may include:
- Subjective optometry: A specific part of the refraction test where the patient provides feedback to find the lenses that improve vision the most. This helps refine the measurement of astigmatism.
- Autorefractometry: This test uses an automated device to measure refractive errors, including astigmatism, without requiring patient feedback.
- Orbscan II: This advanced device evaluates astigmatism by measuring both surfaces of the cornea in specific areas that affect how light is focused (called optical zones). It combines information from an autorefractor and subjective refraction tests to provide a detailed assessment.
These examinations, tests, and procedures help in diagnosing astigmatism and assessing the degree of it and its impact on vision. It is important to consult with an eye specialist for accurate diagnosis and appropriate treatment options.
The goals of treatment for astigmatism are to correct the irregular shape of the cornea or lens and improve visual acuity. Here are the different types of treatments and how they work to achieve these goals:
- Corrective lenses: Glasses or contact lenses with a specific prescription can help focus images properly onto the retina. These lenses have spherical power to correct near or far-sightedness, cylindrical power to correct astigmatism, and an axis measurement to indicate the position of the astigmatism correctly.
- Laser surgery: Some people may opt for laser surgery to correct astigmatism. This procedure uses a laser to reshape the cornea, correcting its irregular shape. Laser surgery can provide long-term improvement in vision.
- Orthokeratology: This treatment involves wearing specially designed rigid contact lenses while sleeping to temporarily reshape the cornea. It does not permanently correct vision but can improve eyesight for several hours after the lenses are removed.
It's important to note that medication types and therapeutic procedures are not typically recommended for treating astigmatism. However, it's always best to consult with your eye care professional for personalized advice and recommendations.