Astigmatism is a refractive error which can cause blurred vision. It’s a common, but usually minor eye condition; similar to myopia (short-sightedness) and hyperopia (long-sightedness).
It’s caused by an unusually-shaped cornea or lens. The cornea or lens is normally curved like a tennis ball, but if you have astigmatism, the shape can be likened to a rugby ball (or American football). If perfectly curved, light focuses on one point at the back of the eye. Astigmatism causes light to be focused on two points, making it difficult to focus on light and causing blurred vision.
Astigmatism can be described as corneal or lenticular. Corneal astigmatism (more common) is where your cornea is not perfectly curved. If your lens is irregularly curved, it is referred to as lenticular astigmatism.
Astigmatism is sometimes inherited and is often present at birth, and can develop as you get older. It can also be caused by an eye injury or operation.
Regular and Irregular Astigmatism
Regular astigmatism is where the refractive error is limited to one area on the cornea/lens. This is the most common form, and is usually corrected quite easily.
Irregular astigmatism is where the cornea is uneven across a number of points on the cornea. It is less common, and usually caused by an eye injury and scarring. It could also be a sign of early keratoconus , a more severe form of astigmatism.
The most common and obvious symptom of astigmatism is blurred vision. Astigmatism often occurs in combination with myopia or hyperopia, and if left untreated may lead to the following additional symptoms:
Regular Astigmatism can be corrected with glasses or contact lenses, or even cured with laser eye surgery. The irregular form can be corrected with contact lenses, but not glasses.
Contact lenses that correct astigmatism are commonly known as toric contact lenses. These have additional measurements which correct your astigmatism; sphere, cylinder and axis.
Your Astimatic Prescription Explained
If you have astigmatism your prescription will normally have a sphere, a cylinder and axis measurement. This may look something like the below:
-1.00(Sphere)/-1.00(Cylinder) x 90 (axis)
The sphere will indicate whether you are myopic or hyperopic. The cylinder will indicate the amount of astigmatism you have and the axis will be the position at where this extra power is needed to correct the irregularity in the cornea or lens.
If you think you may have astigmatism, you should arrange an appointment with your nearest eye care practitioner. Your optometrist can determine whether or not you have astigmatism with a regular routine eye exam, using the same equipment and methods used to detect other refractive errors. You can also take our online astigmatism test , although this is not a replacement for a visit to your Optician.