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Understanding your prescription

How much do you know about your prescription? We're here to help you understand it, as well as the information you'll need to give us when you are booking your consultation.


Did you know?
OD, stands for 'oculus dextrum', which are the readings for your right eye. OS, stands for 'oculus sinistrum', which are the readings for your left eye.

In the box diagram above, you will see 'SPH', which stands for 'SPHERE' and 'D' stands for 'dioptres'. This is the reading that will determine the measurement for how farsighted (hyperopic) and nearsighted (myopic) you are:

  • You are nearsighted if your SPH measurement is minus.
  • You are farsighted if your SPH measurement is plus.
SPH 0-3.0D
SPH 3.0-6.0D
Mild prescription
Moderate prescription
High prescription

What is myopia?

This means you are nearsighted, and struggle to see things that are a distance away, but can focus on things that are near.

What is hyperopia?

This means you are farsighted. You are able to see things that are a distance away but struggle with focusing on things that are nearby.

What is presbyopia?

This comes with the natural aging of the eye, and is the normal deterioration of the near focusing ability of your vision.

What is astigmatism?

Your eyes wouldn't be perfectly spherical, but instead, rugby ball shaped, meaning blurred or distorted vision.

Short-sighted, long-sighted, astigmatism diagram

If you suffer with astigmatism, you would have a measurement in CYL, which stands for 'Cylinder'. Initially, many people believe that this means they aren't eligible for laser eye surgery, but this certainly isn't the case.

Your astigmatism is also measured in 'dioptres' and therefore shown in a plus or minus.
The AXIS would show the position of the CYL (0-180 degrees).

At Ultralase, the SPH and CYL are added together to determine your suitability for laser eye treatment. 

Here is more information around a few more abbreviations that you should know:

VA - this stands for visual acuity. You will be familiar with this measurement if you have been asked to read a Snellen chart in an opticians appointment, which shows various letters that get smaller as you go down the chart. 

Did you know?
Visual acuity is where the term '20/20' comes from.

Optometry eye test

This means an individual can see details from 20 feet away, the same way an individual with normal eyesight would from 20 feet away. If an individual had 20/40 vision, it would mean they can see detail from 20 feet away, that a normal person would see from 40 feet away, meaning that their vision would only be half as good as someone with 20/20 vision.

'Rdg add' would be something that may come up in your prescription if you are over the age of 40-45. This means that you will need two prescriptions; for reading and for distance. This stands for 'reading addition', and highlights the additional positive power that will be needed for eyes to focus for closer work. 

Our focusing ability declines as we get older. This is also known as 'PRESBYOPIA'. 

'Near VA' highlights the smallest sized print that you can read with your prescription. This is usually written as 'Nx' and 'x' shows the print size number. 
N5 is the smallest, and N8 is usually the same size as regular newsprint. 

Do you have any other questions?

Feel free to give our advisers a call on 0800 988 6390 or email us at enquiries@ultralase.com