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How to read your eye prescription

Following your eye test, you'll be given a prescription which will usually be valid for two years. The different numbers and abbreviations show the prescription that you require, but what exactly do these numbers and abbreviations mean? Read on to find out more about how your eyesight is measured.

SPH (Sphere)

This shows the power of the lenses required to correct either long-sightedness or short-sightedness. 

CYL (Cylinder)

This relates to the level of astigmatism that is present in your eyes. Astigmatism occurs when the layer of tissue at the front of your eye (the cornea), or your eye's lens, isn't perfectly curved. Instead, it is oval-shaped. This can cause your eye to bend light incorrectly, resulting in blurred vision.


This shows which position a cylindrical power should be placed to correct for astigmatism.


This is the correction needed to align the eyes, overcoming an eye muscle weakness and ensuring that both look straight and work well together. A prism is a lens that bends the path of light without altering focus.


This added lens power magnifies the image to correct presbyopia. Presbyopia is a condition that causes gradually worsening vision. It usually affects the near aspect of vision.  Symptoms of presbyopia include blurred vision, headaches, and difficulty focusing on objects up close.

If you don’t know your eye prescription, you can book in for an eye test at Optical Express. You should have your eyes examined every two years.

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