How to read your eye prescription

12 September 2019

Author: Kate Green

How to read your eye prescription

Suitability for vision correction treatment


We get lots of questions about optical prescriptions, exactly what the letters and numbers on that piece of paper mean, and whether or not, based on these numbers, someone is suitable for vision correction treatment with us. Depending on where you go for an eye test and who issues your prescription, the information might be laid out differently, confusing things even further! We’ll talk through some of the letters you tend to see on your prescription and explain which aspects of your vision they relate to. This should also help you to determine whether or not you’re suitable for treatment with us, which you can work out by entering your prescription details into our suitability calculator. Alternatively, you can have a quick look at the table below to see if your prescription falls within our basic treatment parameters:



Understanding the details


R and L: Firstly, you’ll see that your prescription details are divided into two sections, R and L. This is very simple to understand: R refers to your right eye, while L refers to your left eye. People’s prescriptions are rarely exactly the same across both eyes, so when you have treatment with us, we vary the laser application, or lens implant, for each eye to make sure you have 20/20 vision in both.


SPH/Sphere: Simply put, this refers to whether you’re long-sighted or short-sighted. Long-sightedness means that you can see objects at a further distance away from you, but struggle to see things close up. Being short-sighted means that you have difficulty seeing into the distance but have no problems seeing objects close to you. Long-sightedness is indicated by a (+) followed by a number while (-) denotes short-sightedness. The closer the number is to zero, the more mild your prescription is. The numbers are presented in increments of 0.25 with the unit of measurement called “dioptres”.


CYL/Cylinder: This gives an indication of whether or not you have astigmatism. Astigmatism is a relatively common condition whereby the eye is shaped more like a rugby ball than being perfectly round, as you might expect. The higher the number of your CYL value, the more severe your astigmatism is. Small astigmatisms are completely normal but if you find yourself suffering from headaches when trying to focus, have tired eyes, or blurry and distorted vision you might have a larger astigmatism. We can treat patients with astigmatism but it depends on the severity, so we can only determine your suitability upon consultation. If the CYL column is left blank on your prescription, you have no astigmatism.


Axis: The axis is also related to the astigmatism but gives the optician, or in our case the surgeon, an indication of how many degrees correction will be needed to give you 20/20 vision. The number will be between 1 and 180, providing details of the position of the cylinder.


Prism: Most prescriptions don’t have a prism value on them, as it usually denotes that a person’s eyes don’t work well together. It typically comes down to muscle imbalance between the two eyes, so your prescription will focus on helping your eyes coordinate and eliminate double vision. People who have glasses to help their near vision or to reduce headaches will probably have a prism value on their prescription. If your prism cannot be corrected by contact lenses, it’s unlikely that you’re suitable for laser eye surgery, as vision correction surgery doesn’t affect the muscle imbalance in the eyes.


Add: Once you reach the age of around 40, the natural lens in your eye begins to deteriorate and harden with age. This means it’s less flexible and so you might struggle to focus on objects close to you. To help with this, many prescriptions of people around this age include a reading addition, which can either be achieved by using additional reading glasses, or by wearing bifocal or varifocal glasses. The value tends to range between +0.75 to +3.00 dioptres and will be the same power in both eyes.


Reading glasses

The need for reading glasses, called presbyopia, can be corrected by treatment at Optimax either by lens treatment, or Monovision laser treatment. With lens treatment, your natural lens is replaced with an artificial one which can either be monofocal, multifocal, or trifocal. As the name suggests, monofocal doesn’t provide any additional focusing abilities, while multifocal allows you to focus on objects both in the distance and close to you. Trifocal is even more advanced, providing the same as a multifocal lens, but with intermediate focus vision included too.


Monovision laser treatment involves treating your non-dominant eye to make it slightly shorted-sighted for better close up vision. Your dominant eye remains untreated, leaving you with good distance vision. Your eyes learn to work together and, between the two of them, can focus on a range of distances. While this might sound a bit strange, it’s actually something that a lot of contact lens wearers already do in order to eliminate the need for reading glasses! If you want to get rid of your readers, get in touch and we can discuss treatment options.


Understanding your prescription is vital if you want to start looking into vision correction surgery. Depending on your prescription details and overall eye health, we will suggest a variety of options for you and recommend the procedure which we think will result in the best vision for you. It is also important for you to have a stable prescription so we can be sure that your visual requirements won’t change over the coming years, affecting the outcome of your treatment with us. Give us a call on 0800 093 1110 or email to start your Optimax journey today.

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