Unless you work in optometry, an optical prescription is likely to look very confusing. The wide range of numbers and abbreviations listed on a prescription follow a consistent format used by opticians across the UK. Here is a basic guide to reading your optical prescription:
The abbreviation “SPH” stands for sphere, which represents the amount of short or long sightedness present. Numbers with a plus in front of them represent corrections for long-sightedness (a difficulty seeing objects that are close to you) while numbers with a minus in front of them represent corrections for short-sightedness (a difficulty seeing objects that are in the distance). The larger the number, the stronger the lens you will require and therefore the thicker your lens will be.
The abbreviation “CYL” stands for cylinder, which represents the amount of astigmatism present. Astigmatism results when your eye is not completely round but is shaped similarly to a rugby ball. It causes your vision to become distorted when you are looking at close up and distant objects. Your cylinder measurement may have a plus or a minus in front of it.
The abbreviation “AXI” stands for axis, which represents the angle at which your lens needs to be set into the frame of your glasses. It is measured as an angle and can be between 0 and 180 degrees.
The “Prism” box represents the amount of correction required to align your eyes so that they are able to work well together. A prism is a type of lens that bends light rays, without altering your eyes’ ability focus. Your prism box may be left blank, in which case no correction is necessary.
The abbreviation “Near ADD” stands for near addition, which represents the amount of correction that must be added over your distance prescription to enable you to see objects clearly when they are viewed close up. While your optician may only list one near addition measurement on your prescription, the near addition power must be added to both of your prescription lenses.
The abbreviation “Int. ADD” stands for intermediate addition, which represents the amount of correction that must be added over your distance prescription to enable you to see objects clearly in the intermediate distance (approximately 65 centimetres away). The intermediate addition measurement is usually only added to your prescription if you intend on having computer glasses made.
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