The higher the number, the more short sighted you are. Mild myopia includes powers up to -3.00 dioptres (D). Moderate myopia, a power of -3.00D to -6.00D. High myopia is usually a power over -6.00D.

You can also get a myopia diagnosis as an adult. When this happens, it's usually due to visual stress or a disease like diabetes or cataracts. You can experience visual stress by spending too much time doing up-close activities, such as reading or doing computer work.

If you are short-sighted, the first number of your spectacle or contact lens prescription will be a negative number e.g. -2.00. A person has low short-sightedness if their prescription is -0.50 to -3.00, and high short-sightedness with -6.00 and higher.

If you're short-sighted, the Sph number is the most relevant. This is given in a measurement called dioptres (D), which describes how severely short-sighted you are. A score of -0.5D to -3D is usually considered to be mild myopia, while a score of more than -6D is considered to be severe or high myopia.