The degree of nearsightedness that is considered high myopia (also known as pathological or severe myopia) is unusually high. High myopia is characterized by an eyeball protruding too far in front of the retina, instead of directly on top of it.
This causes light to enter and focus directly in front of the retina. Distance vision can be blurred while near vision remains clear.
Myopia high is defined as refractive error exceeding -6.00 diopters. However, the severity of myopia can vary from person to person, with some individuals experiencing refractive error greater than -8.00 and even exceeding -10.00. The condition usually appears during childhood or adolescence, and it progresses slowly over time.