Nearsightedness, also known as myopia, is an eye condition that causes blurry distance vision. People who are nearsighted have more trouble seeing things that are far away (such as when driving) than things that are close up (such as when reading or using a computer). If it is not treated with corrective lenses or surgery, nearsightedness can lead to squinting, eyestrain, headaches, and significant visual impairment.\n\nNearsightedness usually begins in childhood or adolescence. It tends to worsen with age until adulthood, when it may stop getting worse (stabilize). In some people, nearsightedness improves in later adulthood.\n\nFor normal vision, light passes through the clear cornea at the front of the eye and is focused by the lens onto the surface of the retina, which is the lining of the back of the eye that contains light-sensing cells. People who are nearsighted typically have eyeballs that are too long from front to back. As a result, light entering the eye is focused too far forward, in front of the retina instead of on its surface. It is this change that causes distant objects to appear blurry. The longer the eyeball is, the farther forward light rays will be focused and the more severely nearsighted a person will be.\n\nNearsightedness is measured by how powerful a lens must be to correct it. The standard unit of lens power is called a diopter. Negative (minus) powered lenses are used to correct nearsightedness. The more severe a person's nearsightedness, the larger the number of diopters required for correction. In an individual with nearsightedness, one eye may be more nearsighted than the other.\n\nEye doctors often refer to nearsightedness less than -5 or -6 diopters as "common myopia." Nearsightedness of -6 diopters or more is commonly called "high myopia." This distinction is important because high myopia increases a person's risk of developing other eye problems that can lead to permanent vision loss or blindness. These problems include tearing and detachment of the retina, clouding of the lens (cataract), and an eye disease called glaucoma that is usually related to increased pressure within the eye. The risk of these other eye problems increases with the severity of the nearsightedness. The term "pathological myopia" is used to describe cases in which high myopia leads to tissue damage within the eye.

Primary or spontaneous detachment of the retina occurs due to underlying ocular disease and often involves the vitreous as well as the retina. The precipitating event is formation of a retinal tear or hole, which permits fluid to accumulate under the sensory layers of the retina and creates an intraretinal cleavage that destroys the neurosensory process of visual reception. Vitreoretinal degeneration and tear formation are painless phenomena, and in most cases, significant vitreoretinal pathology is found only after detachment of the retina starts to cause loss of vision or visual field. Without surgical intervention, retinal detachment will almost inevitably lead to total blindness (summary by McNiel and McPherson, 1971).

A cataract is an opacity or clouding that develops in the crystalline lens of the eye or in its capsule.

A type of retinal detachment arising due to a combination of contracting retinal membranes, abnormal vitreoretinal adhesions, and vitreous changes. It is usually seen in the context of diseases that induce a fibrovascular response, e.g. diabetes.

Diminished clarity of vision.

Fluid which has escaped from retinal blood vessels with a high concentration of lipid, protein, and cellular debris with a typically bright, reflective, white or cream colored appearance on the surface of the retina.

A cataract which affects the layer of the lens surrounding the nucleus, i.e., the lens cortex. It is identified by its unique wedge or spoke appearance.

Nystagmus consisting of horizontal to-and-fro eye movements.

An area of the retina that is buckled so that a sector-shaped sheet of retina lies in front of the normal retina. This feature is of congenital onset.

A nuclear cataract is an opacity or clouding that develops in the lens nucleus. That is, a nuclear cataract is one that is located in the center of the lens. The nucleus tends to darken changing from clear to yellow and sometimes brown.

Separation of the vitreous humor from the retina.

A reduction of previously attained ability to see.

Wasting (atrophy) of the retinal pigment epithelium present in small, isolated areas.

Atrophy of the choroid and retinal layers of the fundus.

A small break in the retina.

A manifest or latent ocular deviation in which one or both eyes tends to deviate nasally.