Uncorrected near-sightedness is one of the most common causes of vision impairment globally along with cataracts, macular degeneration, and vitamin A deficiency. Etymology
The term myopia is of Koine Greek origin: μυωπία myōpia (or μυωπίασις myōpiasis) "short-sight(-ness)", from Ancient Greek μύωψ myōps "short-sighted (man), (man) with eyes getting shut", from μύειν myein "to shut the eyes" and ὤψ ōps "eye, look, sight" (GEN ὠπός ōpos). The opposite of myopia in English is hyperopia (long-sightedness). Signs and symptoms
A myopic individual can see clearly out to a certain distance (the far point of the eye), but objects placed beyond this distance appear blurred. 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.Onset is often in school children, with worsening between the ages of 8 and 15. Causes
The underlying cause is believed to be a combination of genetic and environmental factors. Risk factors include doing work that involves focusing on close objects, greater time spent indoors, urbanization, and a family history of the condition. It is also associated with a high socioeconomic class and higher level of education.A 2012 review could not find strong evidence for any single cause, although many theories have been discredited. Twin studies indicate that at least some genetic factors are involved.
Strongly near-sighted wearers of contact lenses do not experience these distortions because the lens moves with the cornea, keeping the optic axis in line with the visual axis and because the vertex distance has been reduced to zero. Surgery
Refractive surgery includes procedures which alter the corneal curvature of some structure of the eye or which add additional refractive means inside the eye. Photorefractive keratectomy
Photorefractive keratectomy (PRK) involves ablation of corneal tissue from the corneal surface using an excimer laser. The amount of tissue ablation corresponds to the amount of myopia. While PRK is a relatively safe procedure for up to 6 dioptres of myopia, the recovery phase post-surgery is usually painful. LASIK
In a LASIK pre-procedure, a corneal flap is cut into the cornea and lifted to allow the excimer laser beam access to the exposed corneal tissue. After that, the excimer laser ablates the tissue according to the required correction. When the flap again covers the cornea, the change in curvature generated by the laser ablation proceeds to the corneal surface. Though LASIK is usually painless and involves a short rehabilitation period post-surgery, it can potentially result in flap complications and loss of corneal stability (post-LASIK keratectasia). Phakic intra-ocular lens
Instead of modifying the corneal surface, as in laser vision correction (LVC), this procedure involves implanting an additional lens inside the eye (i.e., in addition to the already existing natural lens). While it usually results in good control of the refractive change, it can induce potential serious long-term complications such as glaucoma, cataract and endothelial decompensation.