Myopia

Myopia is a refractive condition in which distant objects appear blurred because light focuses in front of the retina. It is commonly corrected with lenses that move the focal point onto the retina.

Axial length: The distance from the front of the eye to the retina, measured along the eye’s optical axis. An eye that is too long relative to its optical power focuses distant light before the retina.
Eyeglasses: Lenses worn in front of the eyes to correct vision or protect the eyes. Concave spectacle lenses diverge incoming light so distant images focus farther back on the retina.
Emmetropization: The developmental process by which eye growth adjusts toward a balance between axial length and optical power. Failure to maintain this balance during growth can leave the eye myopic.
High myopia: A severe degree of myopia, commonly defined by a refractive error of at least −6.00 diopters. Greater myopic severity is associated with longer eyes and increased risk of retinal complications.
Hyperopia: A refractive condition in which light tends to focus behind the retina when accommodation is relaxed. Its usual focal error lies behind the retina, opposite myopia’s forward focus.
Refractive error: A mismatch between the eye’s optical power and its length that prevents light from focusing sharply on the retina. Myopia is one type of refractive error, alongside hyperopia and astigmatism.
Contact lens: A thin lens worn directly on the eye’s surface to correct vision or serve another optical purpose. A negative-power contact lens corrects myopia while moving with the eye.
Outdoor activity and myopia: The association between time spent outdoors and a lower risk of developing myopia in children. Evidence links outdoor exposure with reduced onset, although it does not fully explain the causes of myopia.
Myopic maculopathy: Degenerative damage to the central retina associated with pathologic myopia. Excessive eye elongation can stretch and damage the macula, impairing central vision.
Astigmatism: A refractive condition in which unequal optical power across meridians causes distorted or blurred vision. Astigmatism arises from direction-dependent focusing, unlike myopia’s principal distance-focus error.

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