Causes of short-sightedness
NHS ChoicesMedical Reference
There is a tendency for myopia to run in families, although it is believed that a number of factors combine to cause myopia.
A person's genetic make-up, and the environment they grow up in, are considered to be linked to the development of myopia.
Blurred vision can also be a symptom of other health problems (see box, right).
Children have an approximately 30% chance of developing myopia if one of their parents has the condition, and a 55% chance if both have it.
People who spend a lot of time reading, working at a computer or doing other close-vision work may develop temporary myopia (where vision returns after resting the eyes). Also, they may be more likely to develop permanent myopia.
Some people develop 'night myopia' - blurred distance vision that only occurs at night. This is because blue light makes the eyes artificially short-sighted, and a small degree of myopia becomes more significant at night.
- Genes contain information that you inherit from your parents, such as eye or hair colour. They are carried by chromosomes.