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What You Should Know About Nearsightedness

Why should we have to keep our eyes’ health? Because it will mean nothing if ewe can not see our beautiful world. We can’t recognize anything that surround us by the face or sight. How if we have eyes disease?
One of common eyes disease is nearsightedness, we also know that by myopia. It causes difficulty seeing objects at a distance. Many people choose soft contact lenses for correction of myopia. Other vision correction choices include glasses, gas permeable contact lenses and eye surgery. The condition can be corrected with eyeglasses, contact lenses or surgery.

* Symptoms
– The primary symptom of nearsightedness is objects in the distance appearing blurred, indistinct and out of focus. The individual cannot read signs or posters from a distance.
– You may have eyestrain or headaches whenever you saw the distant object
– Nearsighted people commonly squint when trying to see distant objects, because this improves focus.
– Vision got blurred and can not see some object rightly.

* Classification
Simple myopia is more common than other types of myopia and is characterized by an eye that is too long for its optical power (which is determined by the cornea and crystalline lens) or optically too powerful for its axial length. Both genetic and environmental factors, particularly significant amounts of near work, are thought to contribute to the development of simple myopia.
Degenerative myopia, also known as malignant, pathological, or progressive myopia, is characterized by marked fundus changes, such as posterior staphyloma, and associated with a high refractive error and subnormal visual acuity after correction.[5] This form of myopia gets progressively worse over time. Degenerative myopia has been reported as one of the main causes of visual impairment.
Nocturnal myopia, also known as night myopia or twilight myopia, is a condition in which the eye has a greater difficulty seeing in low illumination areas, even though its daytime vision is normal. Essentially, the eye’s far point of an individual’s focus varies with the level of light. Night myopia is believed to be caused by pupils dilating to let more light in, which adds aberrations resulting in becoming more nearsighted. A stronger prescription for myopic night drivers is often needed. Younger people are more likely to be affected by night myopia than the elderly.
Pseudomyopia is the blurring of distance vision brought about by spasm of the ciliary muscle.
Induced myopia, also known as acquired myopia, results from exposure to various pharmaceuticals, increases in glucose levels, nuclear sclerosis, oxygen toxicity (e.g., from diving or from oxygen and hyperbaric therapy) or other anomalous conditions. The encircling bands used in the repair of retinal detachments may induce myopia by increasing the axial length of the eye.
Index myopia is attributed to variation in the index of refraction of one or more of the ocular media. Cataracts may lead to index myopia.
Form deprivation myopia is a type of myopia that occurs when the eyesight is deprived by limited illumination and vision range, or the eye is modified with artificial lenses or deprived of clear form vision. In lower vertebrates this kind of myopia seems to be reversible within short periods of time. Myopia is often induced this way in various animal models to study the pathogenesis and mechanism of myopia development.
Nearwork Induced Transient Myopia (NITM), is defined as short-term myopic far point shift immediately following a sustained near visual task.

 

* Cause
Elevation of blood-glucose levels can also cause edema (swelling) of the crystalline lens (hyperphacosorbitomyopicosis) as a result of sorbitol (sugar alcohol) accumulating in the lens. This edema often causes temporary myopia (nearsightedness). A common sign of hyperphacosorbitomyopicosis is blurring of distance vision while near vision remains adequate.

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