What is Astigmatism? 

What is Astigmatism?

Astigmatism is a result of an oblate cornea, not being perfectly round like a football, but rather having a rugby-ball shape. As a result, the light entering the eye is not focused on one point on the retina, but instead multiple points of focus, some of which are behind or in front of the retina, or both.  

It is widely accepted that many people have a certain degree of astigmatism, which is a refractive anomaly of the eye, not a disease, and so is similar to near or farsightedness. 

Signs of Astigmatism

If you suffer from astigmatism, your vision may be blurred at all distances, with objects appearing to have soft edges. Your brain can diminish some of the blurriness, however, if astigmatism is untreated, it can lead to eye strain, headaches, and the squinting of eyes to try to improve clarity. If these symptoms are present, it is best to schedule an eye examination. 

The most common symptoms of astigmatism are: 

• Blurry vision 
• Needing to squint to see clearly
• Headaches 
• Eye strain 
• Trouble seeing at night 

If you have mild astigmatism, you might not notice any symptoms. That’s why it’s important to get regular eye exams — your eye doctor can help you make sure you’re seeing as clearly as possible. This is especially true for children, who may be less likely to realize that their vision isn’t normal. 

What corrective measures are available for astigmatism? 

Prescription lenses can effectively correct astigmatism and your optician is able to accurately measure the amount of astigmatism and provide you with a cylinder prescription to supplement your spherical (SPH) prescription. 

The cylinder and spherical components of the eye’s optical system work in tandem to focus light properly on the retina. The two components are perpendicular to one another, and the ‘axis’ value indicates the orientation of the components. This axis is expressed in degrees and does not denote the intensity of astigmatism, but only the direction. 

If astigmatism is present, your ophthalmic prescription will include a cylinder (denoted as CYL) and an axis. CYL indicates the degree of astigmatism while the axis denotes direction in degrees. It is possible for astigmatism to affect one or both eyes. 

Glasses for Astigmatism 

Usually, when selecting glasses to address myopia or hyperopia, you may follow our advice on other eye conditions from a prescription’s SPH value being positive (+) or negative (-). However, depending on the lens power and axis direction, there may be some instances in which combining the SPH and CYL parts of the lens presents an exception. 

If you require vision correction for astigmatism, specialist contact lenses are also available from opticians, while refractive surgery is also an alternative option. We recommend consulting your prescribing optician first, to explore these possibilities further to understand their benefits and disadvantages before committing to any vision correction.