Myopia is commonly known as nearsightedness or shortsightedness, a condition of the eye where the light ray that goes into the eye does not focus directly on the retina but in front of it. This condition causes the image that the person is looking at from a distance to be out of focus/blurry, but it focus when looking at a close object (Wikipedia). If one has normal vision, the two critical factors,the cornea and the clear front surface of the eye and the crystalline lens, the clear structure inside the eye that changes shape in order to help the eye focus on objects require a perfectly smooth curvature like the surface of a smooth rubber ball. A cornea and lends with such curvature bend, refraction of all incoming light rays in such a way that it makes the image on the retina sharply focused, at the back of one’s eye (MayoClinic).
There are several types of Myopia. Pathological Myopia, which is the condition which the back of the eye ball grows beyond the normal adult size; Secondary Myopia, of which may develop as a result of many different conditions, including premature birth and multiple number of eye diseases; Pseudomyopia, also known as sudden nearsightedness that rapidly grows worse because of another illness, such as uncontrolled diabetes. (WebMD)
In different cases, nearsightedness maybe caused by some other eye problem such as Cataracts and Keratoconus. On the other hand, premature birth may increase the chance of the baby being nearsighted (especially if the baby has retinopathy of prematurity, usually happens to babies born at or before 30 weeks of gestation or those weighing less that 3.3lb. As the immature retina continues to develop after premature birth, abnormal blood vessels may grow around the edges. In severe cases, the retina may detach from the eye) (29th International Congress of Ophthalmology Sydney, Australia, April 2002). People who are severely myopic have a significantly increased risk of glaucoma (an eye disease in which the optic nerve is damaged in a characteristic pattern, it is capable of damaging one’s vision permanently in the affected eye and can even lead to blindness if it is left untreated. It can be caused by dietary reasons, consuming too much caffeine, Genetic heredity etc. Main causes are still unknown) and retinal detachment (Merck Manual Home Edition, “Glaucoma”) Retinal detachment is a disorder of the eye in which the retina is peeled away from its underlying layer of support issue, the initial detachment maybe localized but if the condition is left untreated, the whole retina may detach completely, resulting in partial vision loss or blindness). Myopia is a type of refractive error, if the cornea or lens is not evenly and smoothly curved, light rays are not or can not be refracted properly, it would result in an refractive error (Retinal Detachment - MedilinePlus Medical Encyclopedia)
Eye care professionals mostly correct myopia through the use of corrective lenses, which are either spectacles or contact lenses. Myopia can also be corrected by refractive surgery, also commonly known as LAZIK. The LAZIK surgery is performed by an ophthalmologist who uses a laser or microkeratome to reshape the eye’s cornea in order to improve visual acuity ( Finn, Peter (20 December 2012). For most patients, the LASIK treatment provides a permanent alternative to spectacles or contact lenses. Just like all other surgeries, LASIK also has side effects, Major side effects include halos, starbursts, night-driving problems, keratoconus (the degenerative disorder of the eye in which there are structural changes within the cornea causing it to become thinner and change into a more conical shape, compared to its normal gradual curve) and eye dryness (LASIK complications radial-keratotomy)