Cylinder (CYL)

Cylinder, often abbreviated to CYL, is a number on your eye test prescription that indicates the degree of astigmatism you have. Astigmatism occurs when your cornea or lens is not perfectly round, but rather oval or rugby ball-shaped. As a result, light hits multiple points in your eye, rather than a single sharp point on the retina, causing blurred or distorted vision.

The cylinder value is always given in dioptres and is usually preceded by a minus sign, for example -0.75 or -1.50. The higher the number (in absolute terms), the stronger the cylindrical correction you need. Some people have no cylinder on their prescription, whilst others have a value ranging from mild to strong. The cylinder works in conjunction with the axis, which indicates the direction in which the correction should be applied.

You’ll find the cylinder value on your contact lens or glasses prescription, alongside the sphere (SPH) and the axis. Contact lenses that correct astigmatism are known as toric lenses. Not all lenses have a cylinder value; only people with astigmatism are prescribed a CYL value.

When do you need a cylinder value?

You’ll be given a cylinder value on your prescription if your optician or ophthalmologist detects astigmatism during your eye test. This can occur with even a slight deviation, but also with a more severe distortion. Without cylindrical correction, your vision will remain blurred, particularly when looking at details, letters or lines.

Cylinder in contact lenses

If you have astigmatism and want to wear contact lenses, you’ll need toric lenses. As well as the power, these lenses also have a cylinder and axis value. At SMEYEL , you’ll find contact lenses for astigmatism in various strengths and brands. Always ensure you order the exact CYL and axis values from your prescription, as even a small difference can affect your vision.

Difference between the cylinder value on a glasses prescription and a contact lens prescription

The cylinder value on a prescription for glasses may differ slightly from that on a contact lens prescription, particularly for higher prescriptions. This is because glasses sit further away from your eye than contact lenses. Your optician or optometrist will convert this for you, so always use the correct prescription for the correct product.

No cylinder means no astigmatism

If there is no CYL value on your prescription, or if it says 0.00 or has a dash, then you do not have astigmatism and do not need a cylindrical correction. In that case, you can use standard spherical lenses or spectacle lenses.