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Medically Reviewed
Written by Pooja Rawat, Medical Content Writer
If a CYL (cylindrical) number is mentioned in your eyeglass prescription, you might be wondering, “What does ‘cylindrical eye power’ mean?” Is it different from your normal eye power?
Here is the simple answer for you:
Cylindrical power refers to the amount of correction required to treat astigmatism. Cylindrical power corrects an uneven curvature of the cornea or lens. It is different from spherical power, which corrects nearsightedness or farsightedness.
Astigmatism is a common refractive error that makes your vision blurry, meaning that some part of your eye (either the cornea or the lens) is more curved than it should be. To correct this, eye doctors may prescribe lenses with cylinder power (or cylindrical power) and an axis to compensate for the irregular curve.
What Cylindrical Power Means?
It refers to the lens power prescribed to correct astigmatism.
It is measured in diopters (D) and is written as CYL on an eyeglass or contact lens prescription.
In a normal eye
The cornea (dome-shaped front surface of your eye that protects the eye and helps focus light) is approximately round. This allows entering light to bend evenly and focus on one point on the retina.
With astigmatism
The cornea, or internal lens, has different curvatures in different directions. This makes light that enters your eyes focus as two lines rather than a single point. That uneven focus makes your vision blurry.
Cylindrical power corrects this directional difference in focusing.
What Does Cylindrical Power Mean on an Eye Prescription?
A typical prescription may look something like:
OD: -1.00 -2.00 × 155
Here:
- OD means the right eye.
- -1.00 SPH represents spherical power, commonly used to correct myopia.
- -2.00 CYL represents cylindrical power for astigmatism.
- 155 is the axis, measured in degrees from 0 to 180.
The CYL number tells you how much astigmatism correction is needed. The axis tells the optician where that correction must be positioned.
Cylindrical power can be written as a plus (+) or minus (-) value depending on the prescription convention.
Also Read: How to Increase Eye Power Naturally: Myths vs Facts
In simple words:
The CYL value tells you how much correction is needed, and the axis tells you the exact direction in which that correction needs to be applied.
Spherical vs. Cylindrical Power: What is the Difference
Here is the difference between cylindrical and spherical power:
Feature | Spherical Power | Cylindrical Power |
Prescription abbreviation | SPH | CYL |
Corrects | Myopia or hyperopia | Astigmatism |
Power direction | Same in all meridians | Specific meridian |
Needs an axis? | No | Yes |
Can occur together? | Yes | Yes |
Commonly found in glasses? | Yes | Yes |
Think of the difference with the following analogy:
Spherical power is like adjusting the overall focus of a camera. Cylindrical power corrects a slight distortion in the camera lens itself.
Also Read: Eye Stye(Sty) Explained: Causes, Symptoms, And How To Treat Them
Astigmatism Symptoms
Blurry vision is the most common symptom of astigmatism.
Other symptoms include:
- Seeing glare, halos, or star-like patterns around lights
- Squinting to see clearly
- Headaches
- Fatigue
- Eye strain
Causes of Cylindrical Power
Astigmatism is generally caused by the cornea having an oval or irregular shape.
Your chances of getting cylindrical power increase due to the following risk factors:
- Eyelids putting too much pressure on your eyes
- Genetics.
- Eye injuries
- Conditions like keratoconus or lenticonus
- Complications after eye surgery
- Styes
How to Diagnose Astigmatism
Astigmatism is diagnosed with an eye examination. Your eye doctor may order a complete eye exam that involves both a series of tests to evaluate your eye health and a refraction, which determines how the eyes bend light.
Also Read: What Does 6/6 Vision Mean? A Complete Guide
What is the Treatment for Astigmatism
Most individuals with astigmatism require corrective lenses. Your eye doctor may recommend glasses or contact lenses to help you see clearly.
Types of corrective lenses include:
Eyeglasses
Eyeglasses are made with lenses to help compensate for the uneven shape of the eye. They make the light bend into the eye properly.
Contact lenses
Similar to eyeglasses, contact lenses, which are available in a variety of types and styles, can correct most astigmatism.
Note: Wearing glasses or soft contacts will ensure clear vision. However, they won’t change the shape of your eye.
Refractive Surgery for Astigmatism
After determining your eligibility criteria, your doctor may recommend the following surgeries:
- Laser-assisted in-situ keratomileusis (LASIK)
- Laser-assisted subepithelial keratectomy (LASEK)
- Photorefractive keratectomy (PRK)
- Epi-LASIK (this is a variation of LASEK)
- Small-incision lenticule extraction (SMILE)
FAQ's
What is spherical and cylindrical power?
Can cylindrical power be corrected naturally?
What happens if I have cylindrical power?
Is 1.25 cylindrical eyesight bad?
When should I see my eye doctor?
Signs to See a Doctor Soon
- Persistent blurry or distorted vision
- Eye fatigue or strain after reading or screen use
- Frequent squinting to see clearly
- Headaches tied to visual tasks
- Trouble driving or seeing details at night
Emergency Red Flags
- Sudden blurriness or loss of vision
- Severe eye pain or intense headaches
- Double vision or seeing shadows
- Flashes of light or dark floating curtains
Conclusion
Astigmatism is a common and usually treatable imperfection in the curvature of the eye that causes blurred distance and near vision. It can be managed with glasses or contacts. Talk to an eye doctor about the vision correction method to avoid further complications.
And if you see a CYL number on your prescription, don’t panic. It is not a sign that the prescription is “too bad” or that cylindrical power is damaging your eyes. It is a precise measurement used to help bring your vision into focus.
