If you wear glasses or contact lenses, you probably have some degree of astigmatism. But how much do you really know about this all-too-common refractive error?
Below, we answer some of the most frequently asked questions about astigmatism and explain why scleral contact lenses are often prescribed to astigmatic patients.
1. What is Astigmatism?
Astigmatism is a common refractive error caused by a cornea that isn’t perfectly spherical. The cornea is the outer front covering of the eye and is partially responsible for refracting light onto the retina. When the cornea is misshapen, it refracts light incorrectly, creating two focus points of light entering the eye. Since the light is no longer focused on the retina, it results in blurred vision at all distances.
2. What are the Symptoms of Astigmatism?
The main symptom of astigmatism is blurred vision, but it can also cause symptoms like:
- Objects appearing wavy or distorted
- Poor night vision
- Frequent eye strain
3. How Common is Astigmatism?
Astigmatism affects approximately 1 in 3 individuals around the world. Most people with myopia (nearsightedness) or hyperopia (farsightedness) also have some level of astigmatism.
4. What’s the Difference Between Astigmatism, Nearsightedness and Farsightedness?
Although all 3 of these refractive errors negatively affect visual clarity, they are caused by different mechanisms.
Astigmatism is a result of a non-spherical cornea, which causes two focal points and blurry vision. Myopia occurs when the corneal focusing power is too high and the light focuses in front of, instead of directly, on the retina. Hyperopia occurs when the corneal power is too weak, so the light rays focus behind the retina, not on it. Both myopia and hyperopia can occur with a spherical cornea.
5. How is Astigmatism Corrected?
In cases of mild to moderate astigmatism, the blurred vision can be easily corrected with prescription glasses or contact lenses. But for patients with high levels of astigmatism, standard contact lenses may not be an option. Toric contact lenses are a popular choice for patients with mild or moderate astigmatism due to their unique focusing features and oblong shape. Scleral contact lenses are suitable for moderate to severe astigmatism.
Refractive surgery is also an option, but comes with the risk of surgical complications.
6. Why Can’t Individuals With High Astigmatism Wear Standard Contact Lenses?
A highly astigmatic cornea has an irregularly shaped surface that isn’t compatible with standard soft contact lenses. Standard soft lenses are limited in the amount of astigmatism they can correct, as these lenses move around on the cornea due to the cornea’s irregular shape. This, in turn, reduces visual clarity and comfort.
Regular hard lenses can often correct astigmatism better than soft lenses, but they, too, have limitations: these lenses are smaller and may also move around too much.
7. Why are Scleral Lenses Ideal For Astigmatism?
Scleral contact lenses are customized to each patient. They have a larger diameter than standard lenses, and thus cover the entire front surface of the eye. These specialized rigid lenses gently rest on the white part of the eye (sclera) and don’t place any pressure on the sensitive cornea, making them suitable for even highly astigmatic eyes.
Furthermore, scleral contact lenses contain a nourishing reservoir of fluid that sits between the eye and the inside of the lens, providing the cornea with oxygen and hydration all day long. In fact, patients typically report that sclerals provide sharper vision than other types of contact lenses.
Have Astigmatism? We Can Help
If you’ve been told that you have astigmatism and that your current contacts or glasses just aren’t cutting it, ask your optometrist whether scleral contact lenses are right for you.
At Northwestern Eye Associates Scleral Lens and Keratoconus Center, we provide a wide range of eye care services, including custom scleral lens fittings and consultations. Our goal is to help all patients achieve crisp and comfortable vision, no matter their level of astigmatism or corneal shape.
To schedule your appointment or learn more about what we offer, call Northwestern Eye Associates Scleral Lens and Keratoconus Center today!
Northwestern Eye Associates Scleral Lens and Keratoconus Center serves patients from Mt. Dennis, Toronto, York, and Rockcliffe Smythe, ON and surrounding communities.
Q: Can a person outgrow astigmatism?
- A: About 20% of all babies are born with mild astigmatism, but only 1 of those 5 babies with astigmatism still have it by the age of 5 or 6, at which point it is unlikely to diminish or disappear. Astigmatism can continue to change and even progress as the child grows, but tends to stabilize at around age 25.
Q: Can eye surgery cause astigmatism?
- A: Yes. For example, cataract surgery may cause or worsen astigmatism as the surgeon makes a tiny incision in the cornea to replace the lens. During the healing process, the cornea may change its shape and lead astigmatism to develop.