Myopia

Also known as: Nearsightedness, Short-sightedness

A refractive error in which distant objects appear blurred while near objects remain sharp, caused by an elongated eyeball or excess corneal curvature.

Myopia is the most common refractive error worldwide; global prevalence has roughly doubled in the past 30 years and is projected to affect half the global population by 2050. In children, the eye is still elongating, and prolonged near-focus combined with insufficient outdoor light exposure are the strongest modifiable risk factors. The 20-20-20 rule helps with day-to-day eye strain but is not a primary myopia control intervention; the 20-20-2 rule (2 hours of daily outdoor time) has the strongest evidence for slowing progression in children.