Observing your eye test results, you may have noticed a section labelled "CYL".

If you’re wondering what this strange term means, this article explains what CYL is and what it means in relation to your vision.

Let’s dive in.

 

What does CYL mean on an eye prescription?

CYL stands for Cylinder and refers to the dioptric strength required to correct astigmatism in either or both of your eyes. Astigmatism is a common condition where the cornea or lens of the eye is not perfectly round but slightly curved, resulting in blurred or distorted vision at any distance. The CYL value on your prescription helps to counteract this irregular curvature, thus correcting how light is focused upon your retina.

 

How is CYL measured?

The CYL value on your prescription is measured in dioptres, which is the unit used to measure the optical power of your lenses. A positive (+) or negative (-) number will be assigned depending on the type of astigmatism you have.

Positive values: These indicate farsighted astigmatism.

Negative values: These indicate nearsighted astigmatism.

The higher the absolute value, the more severe your astigmatism. For example, a CYL value of -0.75 means you have mild astigmatism, while a value of -2.50 suggests a higher degree of curvature that requires stronger correction.

If you're buying lenses online, here’s a basic guide on what thickness of lenses to choose based on your SPH and CYL powers.

SPH power	CYL power	Rec. index
up to +/- 2.00	Up to +/- 1.50	1.50 (Standard)
+/-4.00 to 6.75	Up to +/- 2.00	1.60 (Thinned)
+/-7.00 to 9.00	Up to +/- 2.00	1.67 (Super thin)
+/-7.00 to 9.00	+/-2.25 to 6.00	1.74 (Ultra thin)

 

What if CYL is blank?

If the CYL column on your prescription is blank, this simply means that you don’t have significant astigmatism and no correction is needed for that particular eye. In this case, your lenses will be prescribed based on the other values in your prescription, usually just your SPH (sphere) and your ADD (addition) if you need it.

Please note that if you don’t have a CYL value on your prescription, you will, by default, not have an AXIS value either. This is because cylinder and axis are interrelated.

 

How does CYL affect lenses?

CYL mainly affects the price and physical thickness of your lenses; two factors which you should consider if you're buying your lenses online.

For mild CYL values over +/-1.50, it's recommended that you choose thinned lenses with a refractive index of 1.60.

For stronger CYL values over +/-2.50, aim for lenses with a refractive index of 1.67, 1.7 or higher.

As a rule of thumb, the higher your CYL, the higher the refractive index of your lenses should be. The prevents your lenses being overly thick and 'spilling' out the rims of your frame.

Naturally, high index lenses will be more expensive but will save you from having that weird milk bottle look with weird magnified eyes. For extra measure, anti-glare and anti-scratch coatings will prevent reflections on these flatter lenses and keep them lasting longer.

 

CYL FAQs

What is a normal CYL for eyes?

There is no ‘normal’ value when it comes to CYL values. But generally, a CYL measurement between -0.50 and -1.00 dioptres is considered mild astigmatism. Most people with mild astigmatism may not even notice significant issues with their vision, but prescription lenses would still help improve visual clarity.

 

What is a bad astigmatism cylinder number?

A CYL value of +/-1.50 or higher is generally regarded as moderate to high astigmatism. At this level, astigmatism is more likely to cause noticeable visual disturbances, such as blurred or distorted vision, which can be corrected with appropriate lenses.

 

How bad is a 1.50 CYL eye prescription?

A CYL of +/-1.50 indicates moderate astigmatism. While it’s not considered severe, it is enough to cause visual discomfort, particularly with activities that require focus, such as reading or driving at night. Corrective lenses are recommended to sharpen your vision.

 

Should I wear my glasses all the time for astigmatism?

Whether you should wear glasses all the time for astigmatism depends on the severity of your condition. If your astigmatism is mild, you might only need your glasses for tasks like reading, working on a computer, or driving. For higher levels of astigmatism, wearing your glasses more frequently will help prevent eye strain and give you clearer, more comfortable vision throughout the day.

 

What is a high astigmatism CYL?

A CYL value over +/-2.00 dioptres is typically classified as high astigmatism. If you have high astigmatism, it’s recommended that you wear corrective lenses to ensure proper focus and avoid eye fatigue.

 

Hopefully, you found this article helpful. Please check out our other eyecare blogs. Thanks for stopping by.