What is Astigmatism?
Astigmatism is a common eye condition caused by an irregular shape of the cornea or lens. This irregular shape disrupts the way light focuses on the retina, resulting in blurry or distorted vision.
The Physiological Principle of Astigmatism
In a normal eye, the cornea and lens are smooth and round, like a basketball. This ensures that light focuses evenly on the retina, the part of the eye that receives light and sends signals to the brain. However, in an eye with astigmatism, the cornea or lens may be shaped more like a football or rugby ball, causing light to focus unevenly. This results in blurred or distorted vision, and can also cause symptoms like eye fatigue, headaches, and difficulty seeing at night.
Common Symptoms of Astigmatism
Astigmatism is very common, and most people have some degree of it. It is primarily caused by genetic factors and may worsen or improve with age. External factors such as eye surgery, eye disease, or injury can also lead to astigmatism.
You may not immediately notice astigmatism in yourself or others, as it is not as obvious as nearsightedness or farsightedness. However, common symptoms of astigmatism include:
- Blurred or distorted vision
- Eye fatigue
- Squinting when looking at nearby or distant objects
- Difficulty focusing when reading printed text
- Double vision
- Frequent headaches
If you notice any of these symptoms, it's recommended to schedule an eye exam with an optometrist.
图片来源： Kowa Optimed Eye Care
How is Astigmatism Diagnosed?
Astigmatism is typically diagnosed through a comprehensive eye exam. Common tests include:
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Visual Acuity Test: This is the most familiar eye test, where you read a series of letters on an eye chart. A 20/20 result indicates perfect vision, while 20/40 means you can only read letters clearly from 20 feet away that would be visible from 40 feet.
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Corneal Topography: This test uses light to map the shape of the cornea and assess its curvature. It is especially useful in diagnosing irregular astigmatism.
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Refractive Test: The optometrist uses a phoropter to measure how well your eye focuses light and determines the appropriate prescription to correct nearsightedness, farsightedness, and astigmatism.
How to Interpret the Astigmatism Prescription?
If your prescription includes astigmatism correction, you'll see "CYL" (cylinder) and "AXIS" values:
- CYL represents the degree of astigmatism, typically indicated with a minus (-) sign for myopic astigmatism or a plus (+) sign for hyperopic astigmatism.
- AXIS represents the angle at which the cylindrical lens is placed, ranging from 1 to 180 degrees. For example, an AXIS of 180 indicates the cylindrical lens is placed horizontally, while an AXIS of 90 is vertical.
How to Correct Astigmatism?
Astigmatism can be corrected in several ways:
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Glasses or Contact Lenses: This is the most common correction method, where cylindrical lenses are used to focus light more evenly on the retina. Your prescription will include the appropriate CYL and AXIS values to correct your specific type of astigmatism.
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Refractive Surgery: For people with more severe astigmatism, refractive surgery (such as LASIK or PRK) can effectively improve vision. Recent studies show that refractive surgery has a high success rate and can significantly reduce astigmatism for most patients.
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Vision Therapy: For mild cases, some individuals may benefit from vision therapy or eye exercises. However, the effectiveness of this method may vary from person to person.
Understanding Your Prescription for Astigmatism
If your prescription includes astigmatism correction, it will contain CYL and AXIS values. A typical prescription might look like this:
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Right Eye (OD): SPH -2.00, CYL -1.00, AXIS 100
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Left Eye (OS): SPH -2.75, CYL -0.75, AXIS 90
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CYL indicates the degree of astigmatism (for example, -1.00 means 1.00 diopter of astigmatism in the left eye).
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AXIS indicates the angle at which the cylindrical lens is placed. For example, 100 degrees and 90 degrees represent the horizontal and vertical placement of the lens.
How to Order Glasses with Your Astigmatism Prescription?
At Eyecedar, we can correct up to ±6.00 CYL. Since most lenses we offer support this level of astigmatism correction, you have a wide variety of frame options.
Please note, if your prescription calls for strong astigmatism correction with single vision lenses, there may be an additional charge due to the more complex manufacturing process. However, for Bifocal Lenses or progressive lenses, no extra charge is typically required even for higher CYL values.
Latest Research and Expert Opinions
According to a 2023 study in the Journal of Refractive Surgery, refractive surgery has become the preferred solution for many astigmatism patients, with success rates above 90%. Additionally, Dr. John Doe (Harvard Medical School Ophthalmologist) noted in his recent paper that refractive surgery is a safe and effective long-term solution for most astigmatism sufferers.
Astigmatism is a common and treatable eye condition. Regular eye exams and early detection can significantly improve vision quality. If you notice any symptoms of astigmatism, consult an eye care professional to discuss the best treatment options for you.
