MYOPIA

Myopia

Myopia

Description

Myopia is defined as a form of optical refractive error (ametropia) of the eye. It is mostly a result of either an eyeball too long or too heavy for its length, refractive power of the optically active constituents. The result is an aberration that makes distant objects appear blurred than nearby. The degree of myopia is a refraction determined in diopters indicated. It is one of the most common defects in refractive vision consists in the fact that the optical path of the eye focuses light rays properly. Measuring eye with no muscle tone accommodation, focuses parallel light rays precisely on the retina, which is infinitely distant object on the retina will be the sharpest picture. In order to improve visual acuity shortsighted used prescription glasses or contact lenses. These are the lens concave-convex scattering. Their optical power in diopters is given by adding a minus sign. The light rays that pass through the optical means eye (cornea, lens, etc.) are focused within the eyeball, but in front of the retina instead of on the retina. According National Academies Press, (1989) The maximum distance at which a sighted person can see clearly is inversely proportional to the degree of myopia. For example, a myopic -2.00 Diopters able to see clearly at a maximum of 0.5m (50cm) (i.e. 1/2 meter) and no further. Myopia is hereditary and usually appears in childhood. This vision problem may stabilize or progress with age. The severity of myopia is measured in diopters (indicate the power of the corrective lenses necessary to compensate the defect) up to four diopters of myopia is slight and is considered a visual defect in an otherwise healthy eye, 4 to 9 diopters is medium myopia, and myopia greater than 9 dioptres was considered high grade. This is also called pathological, since there is an increased risk of diseases such as ocular chorioretinal or retinal detachment or glaucomapp. 1689).

Before the discussion it is important to know about parts of an eye.

Retina

The retina is the membrane of the inner eye . The sensitive cells to radiation light ( photoreceptors ) are sent to the brain via the optic nerve, which interpret the information. Among the cells that compose the retina must be mentioned: the cones are responsible for color vision but only sensitive to light, rather intense, the rods , which are particularly sensitive to low light intensities, but not the colors.

Cornea

It is convex outer layer of the eyeball in its front. The human cornea is approximately 11.5 mm in diameter and 0.5-0.6 mm thick in the middle part and 0.6-0.8 mm in the peripheral portion. For the cornea is the aqueous and lens by its translucency.

Lense

The lens of the eye is a crystal clear elastic body that both the front and at the rear side stronger convexly curved. It is known in the medical term as the Lens crystallina and bundles as lens through the pupil to light entering the back of the eye so that the retina can ...