Looking at your eye prescription, it can seem like a jumble of confusing numbers and terms.
Understanding what these mean isn’t exactly necessary, but it’d nice to at least have an idea of what’s going on with your precious peppers. An eye prescription is divided into three parts including spherical, cylindrical, and axis.
The term axis plays an important role in correcting specific vision problems. In this article, we'll simply break down what axis means on your eye test results and what it means for your visual correction.
Let’s dive in.
What does Axis mean on your eye prescription?
The axis is a value between 1 and 180 degrees that tells your lens manufacturer exactly where to position the astigmatism correction in your glasses. Astigmatism occurs when the cornea (the front part of your eye) is slightly irregular in shape, meaning it isn't perfectly round. This irregular shape causes light to focus unevenly on your retina, leading to blurry or distorted vision.
The angle of axis tells the lens maker the exact direction along which to correct this astigmatism. In short, it shows where on the eye the cylindrical power should be applied to allow for clear vision. Without the correct axis, your glasses won't properly align with your eye's shape, and your vision could remain blurred.
How does Axis relate to your CYL?
The axis and cylinder (CYL) work together as a team to correct astigmatism - neither measurement is useful without the other.
Cylinder (CYL) tells you how much astigmatism correction you need. This number indicates the strength or power of the cylindrical lens required to compensate for your eye's irregular shape.
Axis tells you where to place that correction. It specifies the precise angle at which the cylindrical power should be oriented in your lens.
For example, a prescription might look something like this:
- SPH: -2.00
- CYL: -1.25
- Axis: 100
How is the Axis Measured?
The axis measurement is expressed in degrees, ranging from 0 to 180. This describes the orientation of the astigmatism on a flat plane. For example, if the axis is 90 degrees, the cylindrical correction would be vertically aligned, while an axis of 180 degrees be horizontally aligned.
How optometrists measure it
There are different ways to identify the correct axis in your eyes.
Phoropter Testing: This is a large instrument with multiple lenses that you look through during your exam. Your optometrist will slowly rotate these different cylindrical lenses and ask you which view appears clearest. This simple test can pinpoint the exact axis of your astigmatism.
Auto-Refractor Analysis: Many eye care professionals also use an auto-refractor, which automatically measures your eye's refractive errors. This computerized device projects light into your eye and analyzes how it reflects back.
Your optometrist determines this value during an eye test using specific equipment designed to asses astigmatism and its orientation. The axis helps ensure that your prescription lenses are accurately aligned with the irregular curve of your cornea.
How the Axis Impacts Your Glasses Lenses
If you have an axis measurement on your prescription, it means your lenses will be customised to correct astigmatism. The axis helps position the cylindrical correction in the right place to ensure clear vision. For people with astigmatism, this precision is key to making sure that light properly focuses on the retina.
If the axis is even slightly off, the lenses won’t function as intended, and you could still experience blurriness or discomfort when wearing your glasses. This is why it’s essential to have an accurate prescription from your optometrist.
FAQs about Axis in eye prescriptions
Can the axis number change over time?
Yes, your axis measurement can change over time, particularly if your astigmatism shifts or your cornea changes shape. Regular eye tests will ensure that your prescription stays accurate.
What happens if my glasses’ axis is incorrect?
Incorrect axis alignment can cause persistent blurred vision, eye strain, and headaches. Even if the cylinder power is correct, placing it at the wrong angle means your astigmatism isn't properly corrected. It’s important to have your prescription checked if you’re experiencing these issues.
Can I wear contact lenses with an axis prescription?
Yes, contact lenses can be made to correct astigmatism. These are known as toric lenses, and they work in a similar way to glasses lenses, with the cylinder and axis providing the necessary correction.
What axis should my eyes be?
There isn’t a specific axis number that your eyes “should” be. The axis is a unique measurement for each person’s astigmatism, ranging from 0 to 180 degrees. It represents the orientation of your astigmatism rather than a “good” or “bad” number. Your optometrist will determine the exact axis that works for your eyes during your eye test.
Is an axis of 180 good or bad?
An axis of 180 is neither inherently good nor bad. It simply means that the astigmatism correction is applied horizontally along the 180-degree line. The key is that the axis is accurate for your eyes, regardless of the specific number.
Can my eye axis be 0?
Yes, an axis can be 0 degrees. This just means that the astigmatism correction is applied along the 0-degree (or horizontal) axis. Like with any other axis number, it’s not a sign of good or bad vision but a measurement specific to the orientation of your astigmatism.
Hopefully, you found this article helpful. Please check out our other eyecare blogs. Thanks for stopping by.