Astigmatism is one of the most common refractive errors. In the US, about 1 in 3 people (or approximately 33% of the population) have some degree of astigmatism. Even though it’s common, there is still confusion about astigmatism and what exactly it means for your vision.
In this post, we discuss seven of the most important astigmatism facts that you need to know.
- Astigmatism is the imperfection of the curvature of the cornea.
Under normal circumstances, the cornea is shaped like a dome. Think of the cornea like a ball or globe, with perfectly symmetrical curves on all sides. With astigmatism, the cornea has asymmetrical curves, which leads to blurry vision from all distances.
- There are two types of astigmatism.
The two types of astigmatism are:
- Corneal astigmatism – Corneal astigmatism means the cornea has an asymmetrical curvature. It is the more common type of astigmatism.
- Lenticular astigmatism – Lenticular astigmatism means it is the lens that has an asymmetrical curvature. It is less common than corneal astigmatism.
Source: Fairview Health Services
- Astigmatism has varying degrees of severity.
The different levels of severity for astigmatism are measured in diopters, and they are:
- Mild astigmatism (less than 1.00 diopter) – Mild astigmatism is considered normal, and individuals who have it often don’t need corrective lenses or surgery to see clearly.
- Moderate astigmatism (1.00 to 2.00 diopters) – The symptoms of moderate astigmatism are already noticeable. Individuals who have moderate astigmatism may be able to function without corrective lenses, but eye care professionals (ECPs) will often recommend the use of corrective lenses.
- Severe astigmatism (2.00 to 3.00 diopters) – Severe astigmatism causes serious symptoms like headaches and eye strain. Individuals who have severe astigmatism will find it difficult to function without wearing corrective lenses.
- Extreme astigmatism (greater than 3.00 diopters) – Individuals with extreme astigmatism are unable to see clearly at all. As such, extreme astigmatism requires treatment in the form of corrective lenses or LASIK surgery.
- Astigmatism has a variety of symptoms that can make it difficult to diagnose
Astigmatism is a common refractive error, and its main symptom is blurred vision. However, astigmatism has several other symptoms which can include:
- double vision
- depth perception problems
- night vision problems
- excessive squinting
- eye strain
Mild astigmatism can be easy to miss. Because the vision is only very slightly blurred, it doesn’t have much of an effect on the individual. Meanwhile, doctors can mistake headaches and eye strain as symptoms of other illnesses, so they don’t refer the patient to an eye care professional. As such, it is possible for individuals to have astigmatism and not even know it, especially if it’s only mild astigmatism.
- There are several ways to diagnose astigmatism.
There are a few different ways to diagnose astigmatism and determine its severity:
- Visual acuity test
The ECP will ask you to read letters on a standard eye chart (the Snellen chart) from 20 feet away to determine your visual acuity, which is denoted in fractions (normal is 20/20 vision).
The numerator (top value) is the standard distance of the test, which is 20 feet. The denominator (bottom value) is the smallest size of letters you were able to read. If you have 20/40 vision, that means you need to be 20 feet away to read what patients with normal vision were able to read from 40 feet away.
- Refraction test
The ECP will place an instrument called a phoropter in front of your eyes. The phoropter contains a series of lenses that measure how the eyes focus light. The ECP will then ask you which lens provides you with the best vision, and your answer will help the ECP determine if you have astigmatism and what your prescription should be.
The ECP will measure the curvature of the anterior (front) surface of your cornea by using an instrument known as a keratometer or ophthalmometer. The keratometer focuses a circle of light onto the cornea and measures its reflection to determine the exact curvature of your cornea. ECPs also use keratometers to determine the proper fit for contact lenses.
- There are several treatment options available for individuals with astigmatism.
Depending on how severe your astigmatism is, you can choose from the following treatment options:
- Eyeglasses – Eyeglasses are ideal if you have mild to moderate astigmatism. Eyeglasses for astigmatism have curved lenses to counter the effect of astigmatism.
- Contact lenses – Contact lenses are also a great treatment option. If you have moderate astigmatism, your ECP may prescribe you soft contact lenses that are specially designed for astigmatism, called toric contact lenses. Unlike regular contact lenses, toric contact lenses have different powers across different meridians of the lens. If you have severe astigmatism, your ECP may prescribe you rigid gas-permeable (RGP) contact lenses.
- Refractive surgery – Commonly known as LASIK or laser eye surgery, refractive surgery permanently changes the shape of your cornea to correct astigmatism. This treatment option is advisable if you have severe to extreme astigmatism, but anyone with astigmatism can choose to get refractive surgery.
- There is a genetic component to astigmatism.
While the exact cause of astigmatism remains unclear, experts agree that astigmatism is linked to genetics. The mismatched curvature of the cornea is a genetic trait like your eye color, hair color, and skin color. Astigmatism is a trait that can be passed down from generation to generation.
Our goal is to educate people about the nature of astigmatism, its effects on daily function, how it’s diagnosed, and the treatment options available. If you have some degree of astigmatism, you may want to consult with your ECP about wearing toric contact lenses. We have a wide range of toric contact lenses available at Lens.com.