Patients always want to know, “Am I nearsighted or farsighted?” but the more they think about it, the more confused they get. It’s really very simple: your prescription is named after what is easier for you to see without glasses. Without glasses, people with nearsightedness (or myopia) see better up close than far away. The larger your prescription, the closer objects need to be for you to see them clearly.

Nearsightedness happens when there is a mismatch between the curvature of the cornea (the clear windshield of the eye) and the length of the eyeball. Either your cornea is too curved, or your eye is too long. Or both!

The number one cause of nearsightedness is… your parents (or grandparents). Genetics play the biggest role in creating myopia but recent studies have shown that the environment also contributes. No, it’s not the amount of reading you do or time spent on electronic devices. The only environmental variable that correlates with nearsightedness is (drum roll, please): time spent outdoors in childhood. Children who spend at least 45 minutes per day outdoors develop less nearsightedness in adulthood than those who don’t regularly spend time outdoors. We don’t know specifically why (yet), but it’s a good idea to regularly chase your kids outdoors to play. It lessens obesity, too.

There are a few advantages to being nearsighted:

But unless you have LASIK surgery, you will need glasses or contacts to see far away.