Myopia often occurs when the eyeball grows too long, preventing the light rays from refracting (bending) correctly. This means that the light coming through doesn't focus in front of the retina (light-sensitive tissue at the back of the eye) - instead, light rays incorrectly focus in front of the retina. Simply put, your eye isn't able to produce a clear image of objects in the distance.

Myopia has the opposite effect of another refractive error, hyperopia (long-sightedness) that makes close objects appear blurred. It's possible to be diagnosed with astigmatism alongside myopia, where your cornea or lens is curved more steeply in one direction, causing your vision to be blurred at any distance. Myopia is usually genetic, but environmental and health factors such as constant visual stress and diabetes are believed to be additional risk factors.

There are three types of myopia:

• Simple myopia: a mild type of the eye condition where the eyeball is otherwise healthy.

• High myopia: a more severe type of myopia that occurs when someone develops nearsightedness at a young age but is left untreated and worsens as they get older. High myopia can increase the possibility of developing other conditions such as glaucoma, cataracts or retinal detachment.

• Pathologic myopia: a rare type of the condition, also known as malignant or degenerative myopia. Pathologic myopia is usually genetic and worsens into adulthood, increasing your chances of experiencing abnormal blood vessel growth, retinal detachment and glaucoma.

What is myopia?