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What does axis mean on my prescription?
Medically reviewed by Alastair Lockwood on 11 December 2020
The axis figure on prescription contact lenses is for people who have astigmatism and indicates the required location of cylindrical power on the lens. This determines the angle of vision correction that someone with astigmatism would need, due to the irregular curvature of their eye, which can be described as shaped like a rugby ball.
Typically given in 10s, the axis figure on a contact lens prescription can be between 1 and 180. Ninety means that the cylindrical power is positioned vertically to correct your astigmatism, whereas 180 would suggest it is positioned horizontally.
What does the cylinder figure mean on my prescription?
The cylinder number on a contact lens prescription is also necessary for those with astigmatism as it indicates the extra power required at the axis to correct the vision of an irregularly curved eye.
The figure can be plus (for long-sightedness) or minus (for short-sightedness) and is always given alongside the usual spherical power on a contact lens prescription.
Those who do not have astigmatism won't find any figures written in the cylinder or axis columns on their prescription.
What does the sphere figure mean on my prescription?
The sphere is measured in dioptres. It indicates the strength of lens prescribed to correct long-sighted and short-sighted vision.
If the SPH number has a minus sign, this means you are near-sighted, whereas a plus sign indicates that you are farsighted.
If you are neither long-sighted nor short-sighted, you may find the infinity symbol or the word Plano written in the sphere column of your prescription. These are equal to zero.
What is the normal eye SPH, CYL, and Axis value?
"Normal" eyes would typically have about 0.50 dioptres of negative cylinder cyl power at an axis number of 180.
Typically, most people have between 0.5 to 0.75 dioptres of astigmatism and won't need contact lenses or glasses to see clearly. Those with astigmatism will have a dioptric power of 1.5 and above.
The axis number becomes irrelevant for those with a dioptre cylinder power of 0.00. A "perfect" eye with no astigmatism has a dioptric sphere power and cylinder power of 0.00.
What does it mean when your eye test says 0.50 in each eye?
A 0.50 measurement is extremely mild whether it is the figure in the sphere, cylinder or axis. If found in the cylinder or axis, this indicates a mild correction for astigmatism.
The larger the measurement, the higher the correction needed.
What are toric contact lenses?
Toric contact lenses are, quite simply, contact lenses that have been specially designed to offer astigmatic correction. Your toric contacts will include a cylinder and axis, which will both be provided on the packaging and on your contact lens prescription.
Quick links:A guide to astigmatism
How do toric contact lenses work?
How to read my contact lens prescription