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Myopia, otherwise known as short sightedness or nearsightedness, is one of the types of eye defects that can occur. The five main classifications for this condition are induced, degenerative, pseudomyopia, simple, and nocturnal. A classification of the condition is dependent on the severity and symptoms.
In terms of vision issues with notable symptoms, this condition is quite common. It is known as a refractive disorder. In a normal eye, light passes through the eye and the retina focuses that light. From the retina, the messages are sent to the optic nerve where the brain processes the signals into images. People with myopia see blurred images from a distance because the retina has not focused properly.
Induced, or acquired, myopia can be a result of several factors. Short sightedness can be caused by an excessive exposure to prescription medications. It can also be caused by nuclear sclerosis or increased glucose. The bands used to repair retinal detachments can stretch the length of the eye, also leading to short sightedness.
Degenerative myopia has an increased amount of refractive error. This category is progressive, which means it will worsen over time. In this case, the eye continues to enlarge and blurred vision increases. This is due to the growing distance between the outer eye and the retina.
Another type of myopia is pseudomyopia. This form is temporary and occurs when the ciliary muscle spasms. The ciliary muscle is the muscle in the eye that controls focusing abilities. Muscle spasms make natural or manual focusing abilities more difficult, resulting in blurred images in the distance.
Simple myopia is the most common form of this condition. The patient's eye is too long for the optical power it has. Genetics and environment can lead to the development of this form. It does not usually progress over time and is often easier to treat.
Nocturnal myopia is classified when a person has trouble seeing things far away when there is low lighting, but daytime vision is normal. Pupils dilate and constrict in response to light levels. When the pupils dilate to allow more light to come into the eyes, a distortion of images occurs.
Most cases of myopia can be treated. There are three methods used to correct this condition. Corrective lenses are special prescription glasses or contacts. Some people with more severe vision problems may also choose to undergo corrective surgery.