Near-sightedness

Near-sightedness
Other namesMyopia, short-sightedness, near-sighted
Myopia.gif
Diagram showing changes in the eye with near-sightedness
SpecialtyOphthalmology
SymptomsDistant objects appear blurry, close objects appear normal, headaches, eye strain[1]
ComplicationsRetinal detachment, cataracts, glaucoma[2]
CausesCombination of genetic and environmental factors[2]
Risk factorsNear work, greater time spent indoors, family history[2][3]
Diagnostic methodEye examination[1]
PreventionMore time outside for children[4]
TreatmentEyeglasses, contact lenses, surgery[1]
Frequency1.5 billion people (22%)[2][5]

Near-sightedness, also known as short-sightedness and myopia, is an eye disorder where light focuses in front of, instead of on, the retina.[1][2] This causes distant objects to be blurry while close objects appear normal.[1] Other symptoms may include headaches and eye strain.[1] Severe near-sightedness is associated with an increased risk of retinal detachment, cataracts, and glaucoma.[2]

The underlying cause is believed to be a combination of genetic and environmental factors.[2] Risk factors include doing work that involves focusing on close objects, greater time spent indoors, and a family history of the condition.[2][3] It is also associated with a high socioeconomic class.[2] The underlying mechanism involves the length of the eyeball growing too long or less commonly the lens being too strong.[1][6] It is a type of refractive error.[1] Diagnosis is by eye examination.[1]

Tentative evidence indicates that the risk of near-sightedness can be decreased by having young children spend more time outside.[4][7] This may be related to natural light exposure.[8] Near-sightedness can be corrected with eyeglasses, contact lenses, or surgery.[1] Eyeglasses are the easiest and safest method of correction.[1] Contact lenses can provide a wider field of vision, but are associated with a risk of infection.[1] Refractive surgery permanently changes the shape of the cornea.[1]

Near-sightedness is the most common eye problem and is estimated to affect 1.5 billion people (22% of the population).[2][5] Rates vary significantly in different areas of the world.[2] Rates among adults are between 15 and 49%.[3][9] Rates are similar in females and males.[9] Among children, it affects 1% of rural Nepalese, 4% of South Africans, 12% of Americans, and 37% in some large Chinese cities.[2][3] Rates have increased since the 1950s.[9] Uncorrected near-sightedness is one of the most common causes of vision impairment globally along with cataracts, macular degeneration, and vitamin A deficiency.[9]

Signs and symptoms

Near-sighted vision (top/left), normal vision (bottom/right)

A myopic individual can see clearly out to a certain distance, but everything further becomes blurry. If the extent of the myopia is great enough, even standard reading distances can be affected. Upon routine examination of the eyes, the vast majority of myopic eyes appear structurally identical to nonmyopic eyes. In cases of high myopia, a staphyloma can sometimes be seen on fundoscopic examination. Because the most significant cause of myopia is the increase in axial length of the eye, the retina must stretch out to cover the increased surface area. As a result, the retina in myopic patients can become thin and might develop retinal holes and lattice degeneration in the periphery. High myopia increases the risk of retinal tears and detachment.