A prescription (also known as an Rx prescription or optical prescription), is a personalised set of values measured by a professional optician or optometrist, which details the lens requirements to correct any vision impairments you may have. A prescription might seem confusing to read, so let us explain some of the main terms, symbols, abbreviations, and numbers.
• OD/OS/OU - These reference the left and right eyes. Many optometrists now use the terms "right eye" (RE) and "left eye" (LE) instead of OD, OS, and OU.
• SPH - SPH is an abbreviation for sphere and it refers to the strength of the lens in your eye. A minus sign (-) denotes nearsightedness, and a plus (+) signs denotes farsightedness.
• CYL - CYL is an abbreviation of 'cylinder' and it refers to the lens power required to correct your astigmatism.
• Axis - The axis measurement is the number that comes before the 'x' on your prescription. It will be within the range of 1 and 180.
• Add - This measurement is the power that assists you with reading and other activities that require focusing at close distance.
• Prism - The prism dioptres measurement on a prescription tells us how to adjust the thick edge of your glasses lens. It is used to correct eye misalignment.
Your prescription may recommend an anti-reflective coating, photochromic lenses, or progressive lenses. You may also find your PD measurement (pupillary distance) listed.