On an eyeglass prescription, “cylinder” (often written as CYL) tells you how much astigmatism your eye has and how strong the correction needs to be for it.

What “cylinder” actually means

  • The cylinder value is the extra lens power built into your glasses to correct an astigmatism , which is an irregular shape of the cornea or lens that makes light focus unevenly.
  • If your prescription has no cylinder number , it usually means you don’t have significant astigmatism.

How it appears on your prescription

  • You’ll see CYL (or “Cylinder”) next to a number like –1.00, +1.50, etc., measured in diopters.
  • A minus cylinder (e.g., –0.75) typically corrects nearsighted astigmatism; a plus cylinder (e.g., +1.25) corrects farsighted astigmatism, depending on the notation your optometrist uses.

Cylinder plus axis

  • Cylinder always comes paired with an axis number (from 0 to 180 degrees), which shows the direction the cylinder power is placed in the lens to match the odd curve of your eye.
  • Together, CYL + axis let the lab make lenses that smooth out your astigmatism so your vision looks clearer and less blurry or distorted.
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Term Role in glasses prescription
Sphere (SPH) Basic power for nearsightedness or farsightedness (spherical correction).
Cylinder (CYL) Extra power needed to correct astigmatism; higher number = stronger astigmatism.
Axis Angle (0–180°) showing where the cylinder power is oriented in the lens.
Information gathered from public forums or data available on the internet and portrayed here.